Section Navigation

Browse



logged in as: pbpl
logout
list users

426 conference proceedings:

Edit | List
title: Transverse dynamics of a short, relativistic electron bunch in a plasma lens
format: conference proceeding
conference: Annual Meeting of the Division of Plasma Physics of the APS
year: 1995
6 authors: G. Hairapetian | P. Davis | C. E. Clayton | C. Joshi | C. Pellegrini | T. Katsouleas
abstract: Dynamic focusing of a 3.8 MeV, 25 ps long, full width at half-maximum (FWHM), electron bunch by an overdense (n/sub p/[right angle bracket][right angle bracket]n/sub b/, where n/sub p/ and n/sub b/ are the plasma and bunch densities, respectively) plasma lens has been studied experimentally. The plasma focused the bunch from an initial transverse size of approximately 2.4 mm (FWHM) to about 0.5 mm, 21 cm downstream of the plasma. The sharp rise time (7 ps 10%-90%) of the electron bunch, excites a large-amplitude ([left angle bracket]1 MeV/m) plasma wave (plasma wake field). The peak focusing force of the lens is partly (60%) due to the beam-generated, azimuthal magnetic field and partly (40%) due to the radial component of the electrostatic wake field. (29 References).
keywords:
Download | Details | Edit | Delete
title: Plasma Lens Experiments at the Final Focus Test Beam
format: conference proceeding
conference: PAC 1993
year: 1993
1 author: Lieu, R.
abstract: We intend to carry out a series of plasma lens experiments at the Final Focus Test Beam facility at SLAC. These experiments will be the first to study the focusing of particle beams by plasma focusing devices in the parameter regime of interest for high energy colliders, and is expected to lead to plasma lens designs capable of unprecedented spot sizes. Plasma focusing of positron beams will be attempted for the first time. We will study the effects of lens aberrations due to various lens imperfections. Several approaches will be applied to create the plasma required including laser ionization and beam ionization of a working gas. At an increased bunch population of 2.5 X 10(10), tunneling ionization of a gas target by an electron beam - an effect which has never been observed before - should he significant. The compactness of our device should prove to be of interest for applications at the SLC and the next generation linear colliders.
keywords:
Download | Details | Edit | Delete
title: An undulator with nonadiabatic tapering for the IFEL project
format: conference proceeding
conference: FEL 2001 23rd
year: 2002
6 authors: A. A. Varfolomeev | S.V. Tolmachev | T. V. Yarovoi | P. Musumeci | C. Pellegrini | J.B. Rosenzweig
abstract: We describe the design of a planar undulator with unusually strong tapering, for the inverse FEL experiment (on the IFEL experiment at the UCLA Neptune Lab. Presented at the 2001 Particle Accelerator Conference, June 18-22, 2001, Chicago, Illinois) to be carried out in Neptune Lab. (Nucl. Instr. and Meth. A 410 (1998) 437) at UCLA. A powerful TW CO_2 laser will be used to accelerate electrons up to 50-60 MeV in 50 cm long undulator. A strong undulator tapering is needed because of the short Rayleigh length of the laser beam. Both the magnetic field and the undulator period are tapered to provide synchronicity of the laser beam interaction with a captured electron bunch along the whole undulator length. The most critical part of the undulator is the region near the laser focus. The main characteristics of the IFEL, such as the percentage of trapped electrons, energy of accelerated electrons and sensitivity to the laser focus transverse position, are given. The general principles of the design of this undulator construction can also be useful for high efficiency FEL amplifiers of intense laser modes.
keywords:
Download | Details | Edit | Delete
title: Large-field-strength short-period undulator design
format: conference proceeding
conference: FEL 1991 13th
year: 1992
6 authors: A. A. Varfolomeev | S. N. Ivanchenkov | A. S. Khlebnikov | C. Pellegrini | Baranov, G. A. | Michailov, V. I.
abstract: A high-quality strong-field hybrid undulator has been designed for an infrared FEL project to be performed at UCLA. The primary magnetic flux is provided by C-shaped vanadium-permendur yokes and SmCo_5 magnets. An additional magnetic flux is supplied by thin NdFeB magnet blocks placed between the yoke poles. This magnet geometry provides a high saturation limit for the magnetic field in the gap area. With the 15 mm period and 5 mm gap a peak on-axis field of 7.3 kG has been achieved. The undulator contains 40 periods. The high accuracy of the yoke poles alignment along with the ability to move the thin permanent magnet blocks provides an on-axis magnetic field accuracy better than 0.5%. (9 References).
keywords:
Download | Details | Edit | Delete
title: Conceptual design of a 300 GeV accelerator based on the Inverse Free Electron Laser mechanism
format: conference proceeding
conference: HEACC 1983 12th
year: 1983
3 authors: C. Pellegrini | P. Sprangle | W. Zakowicz
abstract: The authors describe an Inverse Free Electron Laser Accelerator and how it can be used to accelerate electrons to energies of several hundred GeV, with an average acceleration rate of 150 MeV/m. They discuss the system scaling laws for several undulator designs and the methods for laser beam transport over the required distance of a few kilometers. (9 References).
keywords:
Download | Details | Edit | Delete
title: An inverse free electron laser driven linear collider electron-positron B-factory
format: conference proceeding
conference: PAC 1993
year: 1993
3 authors: N. Barov | C. Pellegrini | Sandweiss, J.
abstract: We discuss an electron-positron linear collider B-Factory using Inverse Free Electron Lasers (IFEL) to accelerate the beams. The requirements on luminosity, larger than 10/sup 33/ cm/sup -2/ s/sup -1/, and energy spread of a B Factory introduce stringent conditions on the accelerator and the interaction region. We study the longitudinal dynamics through the IFEL, the efficiency of the acceleration process, and the ratio of particles which become accelerated, and fall within the resonance. The device is found to perform well in the presence of large variations in the laser field intensity over the beam. We also discuss the laser system powering the IFEL, and some of the system tolerances. (7 References).
keywords:
Download | Details | Edit | Delete
title: Status of the UCLA PEGASUS Injector Laboratory
format: conference proceeding
conference: FEL 2002 24th
year: 2003
6 authors: G. Andonian | P. Frigola | Sven Reiche | J.B. Rosenzweig | S. Telfer | and G. Travish
abstract: The PEGASUS plane wave transformer injector has been conditioned to 20 MW of RF power. Initial operations show a 15 MeV dark current beam that will be used for beam radiation studies. The design of a new LaB_6 cathode will allow for both thermionic emission and photoinjection operation. Experiments currently planned include novel beam instrumentation, surface effects in optical transition radiation, and waveguide SASE FEL.
keywords:
Download | Details | Edit | Delete
title: Progress towards a turn-by-turn beam profile monitor for the Fermilab Booster
format: conference proceeding
conference: Second Annual Workshop on Accelerator Instrumentation
year: 1991
4 authors: J.B. Rosenzweig | V. Bharadwaj | J. Lackey | P. Zhou
abstract: Describes the design and pre-installation testing of a turn-by-turn beam profile monitor for the Fermilab Booster. this non-intrusive monitor collects the ions created by beam particle collisions with the residual gas onto a microchannel plate (MCP) detector using a large (50-100 kV/m) clearing field, to obtain a projected image of the beam distribution in a given plane. The output of the MCP is an anode strip array which gives a 48 channel image with 1.5 mm resolution. The strip current signal is digitized on a turn-by-turn basis to potentially generate more than 16000 beam profiles in one Booster cycle. The purpose of this device is to aid in understanding the effects which drive the transverse emittance growth in the Booster, which may have time scales as short as one turn. (6 References).
keywords:
Download | Details | Edit | Delete
title: Demonstration of electron beam self-focusing in plasma wake fields
format: conference proceeding
conference: Annual Meeting of the Division of Plasma Physics of the APS
year: 1990
10 authors: J.B. Rosenzweig | P. Schoessow | B. Cole | C. Ho | W. Gai | R. Konecny | S. Mtingwa | J. Norem | M. Rosing | J. Simpson
abstract: The direct observation of wake-field self-focusing of an electron beam in plasma is reported. The dynamics of beam self-pinching and the fast collisionless evolution of a Bennett-like, near-equilibrium profile are examined theoretically and computationally. The experimental results are compared to predictions of the analysis and discussed in the context of application to the plasma lens and the plasma wake-field accelerator. (19 References).
keywords:
Download | Details | Edit | Delete
title: Propagation of Short Electron Pulses in Underdense Plasmas
format: conference proceeding
conference: PAC 1993
year: 1993
2 authors: N. Barov | J.B. Rosenzweig
abstract: Our program for an experimental plasma wake field accelerator (PWFA) to take place at the Argonne Wakefield Accelerator (AWA) facility, in the recently proposed blow-out regime relies on the propagation of an intense electron beam through an underdense plasma with a minimum of degradation. This paper presents a near-equilibrium model of beam propagation using the Maxwell-Vlasov equations governing the beam?s transverse behavior. Numerical results are presented which use this model simultaneously with the plasma electron cold fluid equations. A solenoidal magnetic field, which is necessary for high density plasma containment, also provides an initial beam equilibrium to begin the calculation. We compare the equilibrium model with a discrete beam particle simulation, which verifies the basic conclusions of the equilibrium model, and shows the collisionless damping approach to equilibrium in the beam head. The initial matching requirements for the beam?s entry into the plasma are examined. We also discuss the possibility of performing an adiabatic lens experiment.
keywords:
Download | Details | Edit | Delete
title: A fast method to estimate the gain of the microbunch instability in a bunch compressor
format: conference proceeding
conference: FEL 2002 24th
year: 2003
2 authors: Sven Reiche | J.B. Rosenzweig
abstract: To reach high peak currents driving Free-Electron Lasers an initial chirped electron bunch is compressed in a bunch compressor. The interaction of the electron beam with its radiation field can yield a collective instability, which amplifies any initial modulation in the current profile. We present a model, which allows to derive an explicit analytical expression for the gain of the microbunch instability. The results are compared to those of the more complex analytical models.
keywords:
Download | Details | Edit | Delete
title: The UCLA IR FEL project
format: conference proceeding
conference: FEL 1992 14th
year: 1993
21 authors: G. Baranov | N. Barov | P. Davis | M. Fauver | B. Gitter | G. Hairapetian | S. Hartman | M. Hogan | S. Ivanchenkov | C. Joshi | A. Khlebnikov | P. Kwok | N. Luhmann | S. Park | C. Pellegrini | J.B. Rosenzweig | K. Schenk | Smolin, J. A. | P. Tran | G. Travish | A. A. Varfolomeev
abstract: A 10.6 mu m free electron laser (FEL) operating in the high gain regime is under construction at UCLA. FEL physics significant to future short wavelength operation is emphasized including optical guiding, superradiance, saturation and self-amplified spontaneous emission (SASE). A 5 MeV RF photocathode gun illuminated by a UV laser supplies a high brightness electron beam which is injected into a plane wave transformer (PWT) linac for acceleration to 20 MeV. Recent measurements of the gun emittance as well as quantum efficiency are presented. The undulator is of a modified hybrid design producing approximately 7.5 kG peak field on axis with 5 mm gap spacing and 1.5 cm pole period. Simulation results which include three-dimensional effects are furnished. The present status and future plans of the project are summarized. (16 References).
keywords:
Download | Details | Edit | Delete
title: Plasma wake field acceleration: a proposed experimental test
format: conference proceeding
conference: Workshop on Laser Acceleration of Particles 2nd
year: 1985
9 authors: J.B. Rosenzweig | D. B. Cline | R. N. Dexter | D. J. Larson | A. W. Leonard | K. R. Mengelt | J. C. Sprott | F. E. Mills | F. T. Cole
abstract: The prospect of achieving very high accelerating fields has led to proposals for using electrostatic plasma waves to accelerate charged particles for high energy physics. It has been predicted theoretically that these plasma waves can be driven by the wake fields of short bunches, or trains of bunches, of charged particles, to accelerate a subsequent bunch; the longitudinal electric fields could possibly be of the order of a few GV/m. The authors present an outline of a proposed experimental test of this principle. (14 References).
keywords:
Download | Details | Edit | Delete
title: Remarks on short wavelength free electron lasers
format: conference proceeding
conference: Conference on Nonlinear and Relativistic Effects in Plasmas
year: 1992
1 author: C. Pellegrini
abstract: The author reviews the main physics issues and the scaling laws for short wavelength free electron lasers. The author discusses the two main operating modes, oscillator and self amplified spontaneous emission. The author also compares different electron beam drivers, like RF linacs and storage rings. The favourable scaling laws and the recent progress in FELs physics and technology show that the FEL is a good candidate for a tunable soft-X-ray laser. (38 References).
keywords:
Details | Edit | Delete
title: Results of the VISA SASE FEL Experiment at 840 nm
format: conference proceeding
conference: FEL 2002 24th
year: 2003
26 authors: A. Murokh | R. Agustsson | M. BABZIEN | I. Ben-Zvi | L. Bertolini | K. van Bibber | R. Carr | M. Cornacchia | P. Frigola | J. Hill | E. Johnson | L. Klaisner | G.P. Le Sage | M. Libkind | R. Malone | H-D. Nuhn | C. Pellegrini | Sven Reiche | G. Rakowsky | J.B. Rosenzweig | Ruland, R. | Skaritka, J. | A. Toor | A. Tremaine | X. Wang | V. Yakimenko
abstract: VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission (SASE) free-electron laser (FEL), which achieved saturation at 840 nm within a single-pass 4-m undulator. A gain length shorter than 18 cm has been obtained, yielding the gain of 2x10(8) at saturation. The FEL performance, including the spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. The results are compared to 3-D SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL system. Detailed agreement between simulations and experimental results is obtained over the wide range of the electron beam parameters.
keywords:
Download | Details | Edit | Delete
title: A 2 to 4 nm high power FEL on the SLAC linac
format: conference proceeding
conference: FEL 1992 14th
year: 1993
13 authors: C. Pellegrini | J.B. Rosenzweig | Nuhn, H. D. | P. Pianetta | R. Tatchyn | H. Winick | Bane, K. | Morton, P. | T. Raubenheimer | J. Seeman | K. Halbach | K.J. Kim | Kirz, J.
abstract: The authors report the results of preliminary studies of a 2 to 4 nm SASE FEL, using a photoinjector to produce the electron beam, and the SLAC linac to accelerate it to an energy up to 10 GeV. Longitudinal bunch compression is used to increase ten fold the peak current to 2.5 kA, while reducing the bunch length to the subpicosecond range. The saturated output power is in the multi-gigawatt range, producing about 10/sup 14/ coherent photons within a bandwidth of about 0.2% r.m.s., in a pulse of several millijoules. At 120 Hz repetition rate the average power is about 1 W. The system is optimized for X-ray microscopy in the water window around 2 to 4 nm, and will permit imaging a biological sample in a single subpicosecond pulse. (21 References).
keywords:
Download | Details | Edit | Delete
title: Luminosity enhancement in linear colliders using a short focal length plasma lens
format: conference proceeding
conference: UCLA Workshop on Linear-Collider BB Factory Conceptual Design
year: 1987
4 authors: J.B. Rosenzweig | B. Cole | D. J. Larson | D. B. Cline
abstract: It is likely that powerful new focusing methods will be required for the linear colliders of the future. One scheme that shows much promise is plasma focusing in which a particle bunch traversing a plasma is focused by its own wake-fields. The authors present a review of the theory of self pinching due to plasma wake-fields and extend these previous results by discussing how this effect might be of use in constructing a short focal length plasma lens. They then discuss the general properties of short focal length lenses, and the luminosity enhancement that can be theoretically obtained from them. They also examine some of the practical issues involved in installing a plasma lens in a linear collider. (12 References).
keywords:
Download | Details | Edit | Delete
title: Nonlinear plasma and beam physics in plasma wake-fields
format: conference proceeding
conference: Conference on Nonlinear and Relativistic Effects in Plasmas
year: 1992
1 author: J.B. Rosenzweig
abstract: In experimental studies of the plasma wake-field accelerator performed to date at the Argonne Advanced Accelerator Test Facility, significant nonlinearities in both plasma and beam behavior have been observed. The plasma waves driven in the wake of the intense driving beam in these experiments exhibit three-dimensional nonlinear behavior which has as yet no quantitative theoretical explanation. This nonlinearity is due in part to the self-pinching of the driving beam in the plasma, as the denser self-focused beam can excite larger amplitude plasma waves. The self-pinching is a process with interesting nonlinear aspects: the initial evolution of the beam envelope and the subsequent approach to Bennett equilibrium through phase mixing. (35 References).
keywords:
Download | Details | Edit | Delete
title: Quantum efficiency measurements of a copper photocathode in an RF electron gun
format: conference proceeding
conference: PAC 1993
year: 1993
8 authors: P. Davis | G. Hairapetian | C. Clayton | C. Joshi | S. Hartman | S. Park | C. Pellegrini | J.B. Rosenzweig
abstract: A 4.5 MeV photocathode RF gun has been commissioned at UCLA. A photo-injector drive laser produces sub 2 ps pulses of UV ( lambda =266 nm) light with up to 200 mu J/pulse, and illuminates a copper cathode. The photoelectrons are accelerated to an energy of 3.5 MeV within the gun. The electron beam charge is measured as a function of laser energy using an integrating current transformer (ICT). We present measurements of quantum efficiency as a function of laser polarization for injection angles of 2 degrees and 70 degrees with respect to the cathode normal. At 70 degrees incidence a 50% enhancement in quantum efficiency (>10(-4)) is observed for p-polarized light over s-polarized light. (7 References).
keywords:
Download | Details | Edit | Delete
title: Pulse length control in an X-ray FEL by using wakefields
format: conference proceeding
conference: FEL 2002 24th
year: 2003
3 authors: Sven Reiche | P. Emma | C. Pellegrini
abstract: For the users of the high-brightness radiation sources of free-electron lasers it is desirable to reduce the FEL pulse length to 10 fs and below for time-resolving pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of longitudinal wakefields in the undulator and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented.
keywords:
Download | Details | Edit | Delete
title: Slippage, noise and superradiant effects in the UCLA FEL experiment
format: conference proceeding
conference: FEL 1993 15th
year: 1994
5 authors: R. Bonifacio | P. Pierini | C. Pellegrini | J.B. Rosenzweig | G. Travish
abstract: We present the results of numerical calculations of the effects of noise, slippage and superradiance in the UCLA infrared (IR) free electron laser (FEL). The experiment, which uses a high brightness electron beam produced by a photocathode RF gun and a 1.5 cm period planar undulator, compares the FEL evolution starting from noise to that starting from an input signal. Numerical studies indicate that we can observe saturation, optical guiding effects and a superradiant spike.
keywords:
Download | Details | Edit | Delete
title: The LCLS Single-shot Relative Bunch Length Monitor System
format: conference proceeding
conference: Erice 2005
year: 2006
4 authors: Sven Reiche | M. Dunning | G. Travish | J.B. Rosenzweig
abstract: The Particle Beam Physics Lab (PBPL) at UCLA is developing a single-shot relative bunch length monitor system for the Linac Coherent Light Source (LCLS) X-ray Free Electron Laser at SLAC. To ensure high-quality lasing, feedback systems are needed. The bunch length monitor system will be a crucial part of the linac longitudinal feedback system, which is necessary to keep the final peak beam current stable. The system will consist of two multi-channel single-shot grating polychromators, one after each bunch compressor, and will use the coherent synchrotron radiation (CSR) or coherent edge radiation (CER) from bunch compressor chicane dipole magnets. Details of the system will be presented, and the system will be compared to alternatives. Plans for testing and integration into the LCLS beamline will be presented as well.
keywords:
Download | Details | Edit | Delete
title: RF Voltage Modulation at Discrete Frequencies, for Application to Proton Extraction Using Crysal Channeling
format: conference proceeding
conference: PAC 1993
year: 1993
4 authors: Gabella, W. | J.B. Rosenzweig | Kick, R. | Peggs, S.
abstract: RF voltage modulation at a finite number of discrete frequencies is described in a Hamiltonian framework. The theory is applied to the problem of parasitic extraction of protons from a circulating beam in a high energy hadron collider, using a bent crystal as a thin ?septum? extraction element. Three modes of employing discrete resonances are discussed: a strong, single drive resonance which may be used to excite protons to hit, deep within the crystal; a single resonance ramped in such a manner that the island can carry trapped particles from low to high amplitudes; and overlapping resonances to create a chaotic band for separating the moving island and the large amplitude island. Simulations are used to confirm the expected dynamics, and finally a prototypical extraction scheme is described.
keywords:
Download | Details | Edit | Delete
title: Measurements of nonlinear harmonic radiation and harmonic microbunching in a visible SASE FEL
format: conference proceeding
conference: FEL 2002 24th
year: 2003
13 authors: A. Tremaine | X. J. Wang | M. Babzien | I. Ben-Zvi | M. Cornacchia | R. Malone | A. Murokh | H. D. Nuhn | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | Skaritka, J. | V. Yakimenko
abstract: The experimental characterization of nonlinear harmonic generation (NHG) and electron beam microbunching at saturation from a visible SASE FEL are presented in this report. The gain lengths, spectra and energies of NHG were experimentally measured up to the third harmonic, and agree with theoretical predictions. Electron beam microbunching in both the fundamental and the second harmonic as the function of the SASE output were experimentally observed over the full range of SASE gain. The bunching factors for both the fundamental (b(1)) and second harmonic (b(2)) were experimentally characterized at saturation. The microbunching data provides another test of SASE saturation as well as correlating the NHG and electron beam microbunching modes to the fundamental SASE.
keywords:
Download | Details | Edit | Delete
title: A Study of Linewidth, Noise and Fluctuations in a FEL Operating in SASE
format: conference proceeding
conference: FEL 1993 15th
year: 1994
5 authors: Bonifacio, R. | De Salvo, L. | P. Pierini | Piovella, N. | C. Pellegrini
abstract: We study the evolution of the FEL radiation intensity and spectrum starting from noise in the electron beam longitudinal distribution. Due to the slippage both the time and frequency structure of the emitted radiation pulse show a very different behavior when the bunch length is much longer than or of the order of the cooperation length l(c). The occurrence of superradiant spikes is discussed. We present analytical and numerical results.
keywords:
Download | Details | Edit | Delete
title: Chirped-beam two-stage SASE-FEL for high power femtosecond x-ray pulse generation
format: conference proceeding
conference: Conference on Optics for Fourth-Generation X-Ray Sources
year: 2001
5 authors: C. B. Schroeder | C. Pellegrini | Sven Reiche | J. Arthur | P. Emma
abstract: We present a method for generating femtosecond duration x-ray pulses using a single-pass free-electron laser (FEL). This method uses an energy-chirped electron beam to produce a frequency-chirped x-ray pulse through self-amplified spontaneous emission (SASE). After the undulator we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse, and therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE-FEL, and consider the performance of the chirped-beam two-stage option for the Linac Coherent Light Source (LCLS).
keywords:
Download | Details | Edit | Delete
title: PRELIMINARY RESULTS FROM THE UCLA/SLAC ULTRA-HIGH GRADIENT CERENKOV WAKEFIELD ACCELERATOR EXPERIMENT
format: conference proceeding
conference: Erice 2005
year: 2006
12 authors: M.C. Thompson | H. BADAKOV | J.B. Rosenzweig | G. Travish | M. Hogan | R. Ischebeck | N. Kirby | P. Muggli | A. Scott | R. Siemann | D. Walz | R. Yoder
abstract: The first phase of an experiment to study the performance of dielectric Cerenkov wakefield accelerating structures at extremely high gradients in the GV/m range has been completed. This experiment takes advantage of the unique SLAC FFTB electron beam and its demonstrated ultra-short pulse lengths and high currents (e.g., ?z = 20 ?m at Q = 3 nC). The FFTB electron beam has been successfully focused down and sent through varying lengths of fused silica capillary tubing with two different sizes: ID = 200 ?m / OD = 325 ?m and ID = 100 ?m / OD = 325 ?m. The pulse length of the electron beam was varied in the range 20 ?m < ?z < 100 ?m which produced a range of electric fields between 2 and 20 GV/m at the inner surface of the dielectric tubes. We observed a sharp increase in optical emissions from the capillaries in the middle part of this surface field range which we believe indicates the transition between sustainable field levels and breakdown. If this initial interpretation is correct, the surfaced fields that were sustained equate to on axis accelerating field of several GV/m. In future experiments we plan to collect and measure coherent Cerenkov radiation emitted from the capillary tube to gain more information about the strength of the accelerating fields.
keywords:
Download | Details | Edit | Delete
title: Experimental demonstration of plasma lens focusing
format: conference proceeding
conference: PAC 1993
year: 1993
7 authors: G. Hairapetian | P. Davis | C. E. Clayton | C. Joshi | S. Hartman | C. Pellegrini | T. Katsouleas
abstract: The magnetic self-focusing of a relativistic electron beam propagating through a plasma is demonstrated. The plasma which is produced by an RF discharge in a glass tube with no externally applied magnetic field focuses a 3.5 MeV, 25 ps (FWHM) long electron beam from an initial size of 2.5 mm (FWHM) to about 0.5 mm (FWHM) at a focal length of 18 cm. (7 References).
keywords:
Download | Details | Edit | Delete
title: Streak camera measurements of electron bunch length from a copper photocathode in an RF gun
format: conference proceeding
conference: PAC 1993
year: 1993
8 authors: G. Hairapetian | P. Davis | M. Everett | C. Clayton | C. Joshi | S. Hartman | S. Park | C. Pellegrini
abstract: Short laser pulses (sub 2 ps) of UV ( lambda =266 nm) light with 200 mu J/pulse are used to produce electrons from a copper cathode in an RF gun. The electron bunch length is measured by streaking the Cerenkov radiation ( lambda =530 nm) from a thin (250 mu m) fused silica etalon. Streaks for both 0 degrees and 70 degrees laser incidence angles with respect to the cathode normal are presented with a temporal resolution of 3.6 ps. The shortest electron bunch length measured was 9 ps. (3 References).
keywords:
Download | Details | Edit | Delete
title: EXPERIMENTAL TESTING OF DYNAMICALLY OPTIMIZED PHOTOELECTRON BEAMS
format: conference proceeding
conference: Erice 2005
year: 2006
16 authors: J.B. Rosenzweig | A.M. Cook | M. Dunning | R. J. England | P. Musumeci | M. Bellaveglia | M. Boscolo | L. Catani | A. Cianchi | G. Di Pirro | M. Ferrario | D. Filipetto | G. Gatti | L. Palumbo | L. Serafini | C. Vicario
abstract: We discuss the design of and initial results from an experiment in space-charge dominated beam dynamics which explores a new regime of high-brightness electron beam generation at the SPARC (located at INFN-LNF, Frascati) photoinjector. The scheme under study employs the natural tendency in intense electron beams to configure themselves to produce a uniform density, giving a nearly ideal beam from the viewpoint of space charge-induced emittance. The experiments are aimed at testing the marriage of this idea with a related concept, emittance compensation, We show that the existing infrastructure at SPARC is nearly ideal for the proposed tests, and that this new regime of operating photoinjector may be the preferred method of obtaining highest brightness beams with lower energy spread. We discuss the design of the experiment, including developing of a novel time-dependent, aerogel-based imaging system. This system has been installed at SPARC, and first evidence for nearly uniformly filled ellipsoidal charge distributions recorded.
keywords:
Download | Details | Edit | Delete
title: Emittance measurements of the 4.5 MeV UCLA RF photoinjector
format: conference proceeding
conference: PAC 1993
year: 1993
10 authors: S. C. Hartman | N. Barov | S. Park | C. Pellegrini | J.B. Rosenzweig | G. Travish | R. Zhang | P. Davis | C. Joshi | G. Hairapetian
abstract: The 1.5 cell RF photoinjector has been operated for the past several months using a copper cathode illuminated by 4 ps long pulses of UV (246 nm light, with a variable energy of between 0 to 300 mu J. This typically produces up to 3 nC of charge per bunch. Because space charge forces dominate the electron beam transport a pepper pot measurement system is used to measure the emittance. The emittance is measured as a function of charge, peak accelerating field, laser spot size and initial phase with respect to the RF field. This is accomplished with an automated control and data acquisition system which can measure single shot emittances at a rate of 5 Hz developed at UCLA. The experimental results obtained are then compared with theory and simulations. (4 References).
keywords:
Download | Details | Edit | Delete
title: Mitigation of RF Gun Breakdown by Removal of Tuning Rods in High Field Regions
format: conference proceeding
conference: PAC 2007
year: 2007
5 authors: A.M. Cook | M.P. Dunning | J.B. Rosenzweig | K. Serratto | P. Frigola
abstract: The pi-mode resonant frequency of the 1.6 cell SLAC/BNL/UCLA style RF photoinjector electron gun is conventionally tuned using cylindrical copper tuning pieces that extend into the full-cell cavity through holes in the side of the gun. This design begins to fail in many versions of this popular gun design at higher voltage levels, when the cavity undergoes electric breakdown in the vicinity of the tuners. In order to remove the tuners from the region of high electric field, mitigating this problem, one must change the full cell geometry significantly. We have investigated a method for accomplishing this, in which we stretch the gun structure to tune the resonant frequency up by over 2 MHz. We constructed a device to perform this stretching and tested the modified photoinjector in an RF test bed. We succeeded in putting approximately 8.4 MW of RF power into the gun, an improvement over the 4 MW routinely achieved with a similar gun using conventional tuning methods installed at the UCLA Neptune laboratory. Recent results in testing this gun with a magnesium cathode insert are reported as well.
keywords: pbpl  
Download | Details | Edit | Delete
title: A Comparison Between the Performance of Split and Integrated RF Photoinjectors
format: conference proceeding
conference: PAC 1999
year: 1999
4 authors: J.B. Rosenzweig | S. Anderson | X. Ding | L. Serafini
abstract: RF photoinjectors, the present source of choice for production of ultra-high brightness electron beams, have two basic design types: split, in which a short, high gradient rf gun is followed by a a drift and a booster linac, and a lower gradient integrated photoinjector, in which the linac acceleration is connected directly to the gun. The first type is represented at UCLA by the Neptune photoinjector, the second by the newly constructed S-band PWT photoinjector. We examine, through simulation and theory, the relative merits of each type of injector, both from the point of view of the beam physics (ability of the source to produce high currents and low emittances), and of relative technical advantages.
keywords:
Download | Details | Edit | Delete
title: The effects of RF asymmetries on photoinjection beam quality
format: conference proceeding
conference: PAC 1999
year: 1999
4 authors: J.B. Rosenzweig | S. Anderson | X. Ding | D. Yu
abstract: A general multipole-based formalism to study the effects of RF asymmetries on the production of ultra-high brightness beam is presented, which employs both analytical and computational techniques. These field asymmetries can cause the degradation of beam emittance due to time dependent and nonlinear focusing effects. Two cases of interest are examined: the dipole asymmetry produced by a coupling slot in a standard high gradient RF gun, and the higher multipole content introduced by the support/cooling rods in a PWT structure. Practical implications of our results, as well as comparison to cold test and beam-based experimental tests, are discussed. (8 References).
keywords:
Download | Details | Edit | Delete
title: Slab symmetric dielectric micron scale structures for high gradient electron acceleration
format: conference proceeding
conference: PAC 1999
year: 1999
2 authors: P.V. Schoessow | J.B. Rosenzweig
abstract: A class of planar microstructures is proposed which provide high accelerating gradients when excited by an infrared laser pulse. These structures consist of parallel dielectric slabs separated by a vacuum gap; the dielectric or the outer surface coating are spatially modulated at the laser wavelength along the beam direction so as to support a standing wave accelerating field. We have developed numerical and analytic models of the accelerating mode fields in the structure. We show an optimized coupling scheme such that this mode is excited resonantly with a large quality factor. The status of planned experiments on fabricating and measuring these planar structures is described. (9 References).
keywords:
Download | Details | Edit | Delete
title: The UCLA/NICADD Plasma Density Transition Trapping Experiment
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: M.C. Thompson | W. Lu | W. Mori | J.B. Rosenzweig | G. Travish | N. Barov
abstract: Plasma density transition trapping is a recently purposed self-injection scheme for plasma wake-field accelerators. This technique uses a sharp downward plasma density transition to trap and accelerate background plasma electrons in a plasma wake-field. Two and three dimensional Particle-In-Cell (PIC) simulations show that electron beams of substantial charge can be captured using this technique, and that the beam parameters such as emittance, energy spread, and brightness can be optimized by manipulating the plasma density profile. These simulations also predict that transition trapping can produce beams with brightness > 5x10^14 Amp/(m-rad)^2 when scaled to high plasma density regimes. A proof-of-principle plasma density transition trapping experiment is planned for the near future. This experiment is a collaboration between UCLA and the Northern Illinois University (NICADD). The goal of experiment is to capture a ~100 pC beam with ~4% rms energy spread out of a 2 x 10^13 cm^-3 peak density plasma using a ~6nC, 14 MeV drive beam. Status and progress on the experiment are reported.
keywords:
Download | Details | Edit | Delete
title: Plasma Lens Experiments at the Final Focus Test Beam
format: conference proceeding
conference: PAC 1993
year: 1995
33 authors: R. Lieu | W. Barletta | S. Chattopadhyay | P. Chen | D. B. Cline | W. Craddock | W. Gabella | I. Hsu | R. Iverson | T. Katsouleas | P. Kwok | P. Lai | W. Leemans | R. Liou | D. Meyerhofer | K. Nakajima | H. Nakanishi | C. K. Ng | Y. Nishida | J. Norem | A. Ogata | S. Rajagopalan | T. Shintake | J.B. Rosenzweig | M. Ross | A. Sessler | J. Spencer | J. J. Su | N. Walker | G. Westenskow | D. Whittum | R. Williams | J. Wurtele
abstract: We intend to carry out a series of plasma lens experiments at the Final Focus Test Beam facility at SLAC. These experiments will be the first to study the focusing of particle beams by plasma focusing devices in the parameter regime of interest for high energy colliders, and is expected to lead to plasma lens designs capable of unprecedented spot sizes. Plasma focusing of positron beams will be attempted for the first time. We will study the effects of lens aberrations due to various lens imperfections. Several approaches will be applied to create the plasma required including laser ionization and beam induced tunneling ionization of a working gas - the latter which has never been observed before. The compactness of our device should prove to be of interest for applications at the SLC and the next generation linear colliders.
keywords:
Download | Details | Edit | Delete
title: Underdense plasma lens experiment at the UCLA Neptune Laboratory
format: conference proceeding
conference: PAC 1999
year: 1999
10 authors: Suk, H. | C. E. Clayton | G. Hairapetian | C. Joshi | Loh, M. | P. Muggli | R. Narang | C. Pellegrini | J.B. Rosenzweig | T.C. Katsouleas
abstract: An underdense plasma-lens experiment is planned at the UCLA Neptune Laboratory. For this experiment, a LaB/sub 6/-based discharge plasma source was developed and tested. Test results of the plasma source show that it can provide satisfactory Ar plasma parameters for underdense plasma lens experiments, i.e., a density in the low 10/sup 12/ cm/sup -3/ range and a thickness of a few cm. In the plasma chamber a YAG slab and a Cherenkov radiator are placed for electron beam diagnostics so that both time-integrated and time-resolved information will be obtained and compared with the MAGIC code (2 and 1/2 dimensional particle-in-cell) simulations. In this paper, the planned experiment including test results of the plasma source, diagnostics and MAGIC simulation results is presented. (5 References).
keywords:
Download | Details | Edit | Delete
title: Acceleration of Injected Electrons In A Laser Beatwave Experiment
format: conference proceeding
conference: PAC 2003
year: 2003
10 authors: S. Ya. Tochitsky | R. Narang1 | C.V. Filip1 | P. Musumeci | C.E. Clayton | R. Yoder | K.A. Marsh1 | J.B. Rosenzweig | C. Pellegrini | and C. Joshi11
abstract: Plasma-based accelerators of particles are of great interest because plasmas can sustain very strong electric fields. They are utilizing a relativistic plasma wave with a phase velocity close to the speed of light driven by a high-power laser beam. The Neptune Laboratory at UCLA is being used for plasma beatwave acceleration of injected electrons. Here, a two-wavelength laser pulse (frequencies w1,w2) resonantly drives a longitudinal electron plasma wave of frequency equal to w1-w2, providing a field strength of GeV/m and, therefore, accelerates an injected electron beam at this very high gradient. A 10 ps beam of 12 MeV electrons is loaded in a 3-cm long plasma beatwave accelerator driven by a TW CO2 laser pulse. At the resonance condition, the electrons have been accelerated to 50 MeV with a gradient of ~1.3 GeV/m. It is shown that for large volume diffraction limited plasmas, when efficiency of the plasma wave excitation is restricted by ionization-induced refraction, acceleration of electrons is enhanced significantly by using asymmetric (fast front and slow fall) long pulses. 2D PIC simulations revealed that guiding of the laser pulse in a ponderomotive, self-induced ion channel, formed ~200 ps after the field ionization, allows compensation for the ionization-induced defocusing and efficient driving of the beatwave over the entire length.
keywords:
Download | Details | Edit | Delete
title: A linear collider phi factory and beam dynamics test machine
format: conference proceeding
conference: Workshop on CP Violation in Particle Physics and Astrophysics
year: 1990
8 authors: W.A. Barletta | R. C. Berg | A. Boden | C. Buchanan | D.B. Cline | A. Fridman | C. H. Ho | C. Pellegrini
abstract: The authors present the design of a high luminosity linear collider phi factory. This machine can be used to search for violation of CPT invariance and the study of CP violation (epsilon). It can also serve as a test collider to study the feasibility of L > 10(34) cm(-2) sec(-1) BB factory and the beam dynamics of large disruption systems. The machine will be asymmetric in beam energy, thus giving the phi's a boost.
keywords:
Details | Edit | Delete
title: A measurement of high gain SASE FEL induced electron beam micro-bunching using coherent transition radiation
format: conference proceeding
conference: PAC 1999
year: 1999
9 authors: A. Tremaine | S. Anderson | Pedro Frigola | M. Hogan | A. Murokh | C. Pellegrini | J.B. Rosenzweig | D. C. Nguyen | Sheffield, R.
abstract: Coherent transition radiation (CTR) was used to study the longitudinal modulations of an electron beam exiting the UCLA/LANL high gain SASE FEL. The induced longitudinal micro-bunching of the electron beam at the exit of the undulator was measured with a frequency domain technique using the CTR emitted when this beam strikes a thin conducting foil. Formalisms for both CTR and SASE theories are related using the simulation code GINGER in which the SASE FEL gain of the output radiation and the micro-bunching of the electron beam are given. Experimental results from the CTR measurement will show the limit of standard transition radiation theory is being approached and new analysis is needed. (8 References).
keywords:
Download | Details | Edit | Delete
title: The Brookhaven free electron laser experiment
format: conference proceeding
conference: Bendor Free Electron Laser Conference
year: 1983
5 authors: S. Krinsky | A. Luccio | C. Pellegrini | A. van Steenbergen | L. H. Yu
abstract: Reports on the status of the free electron laser experiment at Brookhaven with a description of the permanent undulator already built and ready to be installed on the VUV storage ring. (0 References).
keywords:
Download | Details | Edit | Delete
title: A permanent-magnet focused X-band photoinjector
format: conference proceeding
conference: PAC 1999
year: 1999
8 authors: D. Yu | D. Newsham | Wilson, P. | Zeng, J. | J.B. Rosenzweig | X. Ding | F. Hartemann | Landahl, E.
abstract: A Plane-Wave-Transformer (PWT), integrated photoinjector operating at an X-band frequency (8.547GHz) is being developed by DULY Research Inc. in a DOE SBIR project, in collaboration with UCLA and UCD/ILSA. Upward frequency scaling from an S-band PWT photoinjector would result in a compact photoinjector with unprecedented brightness. Challenging technological innovations are required at X-band. In particular, water cooling capacity, mechanical support strength, and materials properties do not scale linearly with frequency. Instead of using large solenoids, we have successfully designed the required focusing for an X-band PWT using a compact, permanent magnet system. Also described in this paper is a system design of the X-band photoinjector, including the RF system and the cooling/support of the PWT structure.
keywords:
Download | Details | Edit | Delete
title: The UCLA Pegasus Plane-Wave Transformer Photoinjector
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: G. Travish | G. Andonian | P. Frigola | Sven Reiche | J.B. Rosenzweig | and S. Telfer
abstract: A photoinjector based on a multicell plane wave transformer accelerating structure has been commissioned at the UCLA Department of Physics' Pegasus Laboratory. Design and construction of the novel structure have been previously reported [J. Rosenzweig, et al. PAC Proceedings 1997], and recent operation with a thermionic cathode is being presented at this conference [P. Frigola, et al. these proceedings]. This paper describes the planned operation of the PWT gun as a photoinjector, including design and construction details of the drive laser. Progress to date and future plans are discussed.
keywords:
Download | Details | Edit | Delete
title: Analysis of the Evolution of Classical Distribution Functions Using Quantum Methods
format: conference proceeding
conference:
year: 1998
1 author: J.B. Rosenzweig
abstract:
keywords:
Download | Details | Edit | Delete
title: X-Band Dipole Mode Deflecting Cavity for the UCLA Neptune Beamline
format: conference proceeding
conference: PAC 2005
year: 2005
5 authors: R. J. England | B. O'Shea | J.B. Rosenzweig | G. Travish | D. Alesini
abstract: We report progress on the design and construction of a nine-cell cavity operating in a TM110-like dipole mode for use as a temporal diagnostic of the 14 MeV, 300 pC electron bunches generated at the UCLA Neptune Laboratory linear accelerator, with an anticipated temporal resolution of 50 fs at a peak input power of 50 kW. The cavity is a center-fed standing-wave pi-mode structure, operating at 9.6 GHz, and incorporating a knife-edge and gasket assembly which minimizes the need for brazing or welding. Results of initial RF testing of the prototype cavity are discussed and compared with simulation results obtained using the commercial code HFSS.
keywords:
Download | Details | Edit | Delete
title: Nonlinear beam dynamics experimental program at SPEAR
format: conference proceeding
conference: Workshop on Nonlinear Dynamics in Particle Accelerators: Theory and Experiments
year: 1995
5 authors: P. Tran | C. Pellegrini | M. Cornacchia | M. Lee | W. Corbett
abstract: Since nonlinear effects can impose strict performance limitations on modern colliders and storage rings, future performance improvements depend on further understanding of nonlinear beam dynamics. Experimental studies of nonlinear beam motion in three-dimensional space have begun in SPEAR using turn-by-turn transverse and longitudinal phase-space monitors. This paper presents preliminary results from an on-going experiment in SPEAR. (10 References).
keywords:
Download | Details | Edit | Delete
title: Optimization of an X-ray SASE FEL
format: conference proceeding
conference: ICFA Beam Dynamics Workshop on Physics of, and Science with, the X-Ray Free-Electron Laser 19th
year: 2001
7 authors: C. Pellegrini | Sven Reiche | J.B. Rosenzweig | C. Schroeder | A. A. Varfolomeev | Tolmachev, S. | H-D. Nuhn
abstract: The most important characteristics of an X-ray SASE-FEL are determined by the electron beam energy, transverse and longitudinal emittance, and by choice of the undulator period, field, and gap. Among them are the gain and saturation length, the amount and spectral characteristics of the spontaneous radiation, the wake fields due to the vacuum pipe. The spontaneous radiation intensity is very large in all X-ray SASE-FELs now being designed, and it contributes to the final electron beam energy spread, thus affecting the gain. It also produces a large background for the beam and radiation diagnostics instrumentation. The wake fields due to the resistivity and roughness of the beam pipe through the undulator, also affects the beam 6-dimensional phase space volume, and thus the gain and the line width. In this paper, we discuss ways to optimize the FEL when considering all these effects. In particular we consider and discuss the use of a hybrid iron-permanent magnet helical undulator to minimize some of these effects, and thus optimize the FEL design.
keywords:
Download | Details | Edit | Delete
title: Measurements of Copper RF Surface Resistance at Cryogenic Temperatures for Applications to X-Band and S-Band Accelerators
format: conference proceeding
conference: IPAC 2016
year: 2016
11 authors: A. Cahill | A. Fukasawa | J.B. Rosenzweig | Y. Higashi | G.B. Bowden | V.A. Dolgashev | J. Guo | M. Franzi | S. Tantawi | P.B. Welander | C. Yoneda
abstract: Recent SLAC experiments with cryogenically cooled X- band standing wave copper accelerating cavities have shown that these structures can operate with accelerating gradi- ents of 250 MV/m and low breakdown rates. These results prompted us to perform systematic studies of copper rf prop- erties at cryogenic temperatures at low rf power. We placed copper cavities into a cryostat with a cryocooler, so the cavities could be reduced to 4K. We used different shapes of cavities for the X-band and S-band measurements. RF properties of the cavities were measured using a network analyzer. We calculated rf surface resistance from measured Q 0 at temperatures from 4 K to room temperature. The re- sults were then compared to the theory proposed by Reuter and Sondheimer. These measurements are part of studies with the goal of reaching very high operating accelerating gradients in normal conducting rf structures.
keywords:
Download | Details | Edit | Delete
title: Recent Results from and Future Plans for the VISA II SASE FEL
format: conference proceeding
conference: PAC 2005
year: 2005
19 authors: G. Andonian | R. Agustsson | P. Frigola | A. Murokh | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | G. Travish | M. BABZIEN | I. Ben-Zvi | V. Litvinenko | V. Yakimenko | I. Boscolo | S. Cialdi | A. Flacco | M. Ferrario | L. Palumbo | C. Vicario | J. Huang
abstract: The VISA II (Visible to Infrared SASE Amplifier) project, a consequent experiment to the succesful VISA enterprise, entails the use of a chirped electron beam to drive a high gain SASE FEL. The resulting ultra-short pulses will be characterized using an advanced FROG (Frequency Resolved Optical Gating) technique, as well as a double differential spectrum (angle/wavelength) diagnostic. Implementation of sextupole corrections to the longitudinal aberrations affecting the high energy-spread chirped beam during transport to the VISA undulator is studied. Start-end simulations, including radiation diagnostics, are discussed. Initial experimental results involving a highly chirped beam transported without sextupole corrections, the resulting high gain lasing, and computational analysis are briefly reported.
keywords:
Download | Details | Edit | Delete
title: RF Design of the UCLA/INFN Hybrid SW/TW Photoinjector
format: conference proceeding
conference:
year: 2006
9 authors: J.B. Rosenzweig | Alessandro Boni | A. Fukasawa | D. Alesini | Massimo Ferrario | Bruno Spataro | Luca Ficcadenti | Andrea Palumbo | B. O'Shea
abstract: With increasing demand for high brightness, low emittance beams for use with freeelectron lasers, Compton scattering systems and wake-field accelerator experiments, stringent requirements have been placed on the design and operation of the 1.6 cell photoinjector. The proposed hybrid photoinjector combines the BNL/UCLA/SLAC style 1.5/1.6 cell standing wave gun with a traveling wave accelerator. Our goal is an injector that meets today’s requirements and is scalable in design to meet tomorrow’s demands: emittances in the region of 1 mm-mrad for higher brightness as well as higher currents. The hybrid photoinjector also offers higher energy operation, enhanced cost effectiveness and better scalability than current designs such as integrated PWT photoinjectors and split gun/accelerating sections. The use of both SW and TW systems allows for higher gradients (Eo = 70 MV/m) in the SW gun for effective capture at lower emittances, while the lower energy acceleration in the TW sections (Eo = 13.5 MV/m) allows generation of higher energy beams which are less sensitive to space charge effects. We note the current results of simulation of beam dynamics, en,x = 3 mm-mrad, an energy spread of 1.5% with beam energies of 21 MeV at currents as high as 1.2 kA. Further we explore the possibilities of scalability to higher frequencies, analysis of coupling design, present cold test preparations and simulated RF analysis of the structure.
keywords:
Download | Details | Edit | Delete
title: Beam collimation for LCLS beam emittance and charge control
format: conference proceeding
conference: ICFA Beam Dynamics Workshop on Physics of, and Science with, the X-Ray Free-Electron Laser 19th
year: 2001
3 authors: C.B. Schroeder | H. D. Nuhn | C. Pellegrini
abstract: We describe an electron beam collimator for the linac coherent light source (LCLS). The collimator reduces both the transverse emittance and the total charge of the electron beam. Beam optics are designed to increase the beam spot size for collimation. The impedance of the collimator is calculated, and the wakefield induced emittance growth is determined. (12 References).
keywords:
Download | Details | Edit | Delete
title: Production of High Harmonic X-ray Radiation from Non-linear Thomson Scattering at LLNL PLEIADES
format: conference proceeding
conference: PAC 2005
year: 2005
11 authors: J. Lim | A. Doyuran | P. Frigola | G. Travish | J.B. Rosenzweig | S. Anderson | S. Betts | J. Crane | D. Gibson | F. Hartemann | A. Tremaine
abstract: We describe an experiment for production of high harmonic x-ray radiation from Thomson backscattering of an ultra-short high power density laser by a relativistic electron beam at the PLEIADES facility at LLNL. In this scenario, electrons execute a ``figure-8'' motion under the influence of the high-intensity laser field, where the constant characterizing the field strength is expected to exceed unity: $a_{L}=eE_{L}/m_{e}c\omega_{L}\geq1$. With large $a_{L}$ this motion produces high harmonic x-ray radiation and significant broadening of the spectral peaks. This paper is intended to give a layout of the PLEIADES experiment, along with progress towards experimental goals.
keywords:
Download | Details | Edit | Delete
title: Measurements of high gain and noise fluctuations in a SASE free electron laser
format: conference proceeding
conference: FEL 1997 19th
year: 1998
12 authors: M. Hogan | S. Anderson | K. Bishofberger | P. Frigola | A. Murokh | N. Osmanov | C. Pellegrini | S. Reiche | J.B. Rosenzweig | G. Travish | A. Tremaine | A.A. Varfolomeev
abstract: We report measurements of large gain for a single pass free-electron laser operating in self-amplified spontaneous emission (SASE) at 16 mu m starting from noise. We also report the first observation and analysis of intensity fluctuations of the SASE radiation intensity in the high-gain regime. The results are compared with theoretical predictions and simulations. (11 References).
keywords:
Download | Details | Edit | Delete
title: The design for the LCLS RF photoinjector
format: conference proceeding
conference: FEL 1998 20th
year: 1999
16 authors: R. Alley | Bharadwaj, V. | Clendenin, J. E. | P. Emma | Fisher, A. | Frisch, J. | Kotseroglou, T. | R. H. Miller | D. T. Palmer | Schmerge, J. F. | Sheppard, J. C. | Woodley, M. | Yeremian, A. D. | J.B. Rosenzweig | D. Meyerhofer | L. Serafini
abstract: We report on the design of the RF photoinjector of the Linac Coherent Light Source. The RF photoinjector is required to produce a single 150 MeV bunch of similar to 1 nC and similar to 100 A peak current at a repetition rate of 120 Hz with a normalized rms transverse emittance of similar to 1 pi mm-mrad. The design employs a 1.6-cell S-band RF gun with an optical spot size at the cathode of a radius of similar to 1 mm and a pulse duration with an rms sigma of similar to 3 ps. The peak RF field at the cathode is 150 MV/m with extraction 57 degrees ahead of the RF peak. A solenoidal field near the cathode allows the compensation of the initial emittance growth by the end of the injection linac. Spatial and temporal shaping of the laser pulse striking the cathode will reduce the compensated emittance even further. Also, to minimize the contribution of the thermal emittance from the cathode surface, while at the same time optimizing the quantum efficiency, the laser wavelength for a Cu cathode should be tunable around 260 nm. Following the injection linac the geometric emittance simply damps linearly with energy growth. PARMELA simulations show that this design will produce the desired normalized emittance, which is about a factor of two lower than has been achieved to date in other systems. In addition to low emittance, we also aim for laser amplitude stability of 1% in the UV and a timing jitter in the electron beam of 0.5 ps rms, which will lead to less than 10% beam intensity fluctuation after the electron bunch is compressed in the main linac.
keywords:
Download | Details | Edit | Delete
title: The UCLA IR-FEL
format: conference proceeding
conference: IEEE International Conference on Plasma Science 1990
year: 1990
11 authors: F. Aghamir | W. Barletta | D. B. Cline | J. Dodd | S. Hartman | C. Joshi | J. Kolonko | N. Luhmann | D. McDermott | C. Pellegrini | C. Terrien
abstract: A high-brightness RF gun operating at 2.856 GHz is being used as the injector for an IR-FEL (free-electron laser) experiment. The RF gun consists of a disk loaded, 1.5 cell cavity and a photocathode in the end wall of the cavity. A strong electric field within the half cell near the photocathode quickly accelerates the electrons, thus preventing emittance blow-up. The photocathode is to be driven by a Nd:YAG laser system producing a 10-ps pulse. The power for the RF gun will be supplied by a 25-MW klystron. The RF power is coupled to the cavity via an S-band waveguide attached to the sidewall of the gun. The TE_10 mode excited in the waveguide strongly couples to the pi-mode with the RF gun while the zero mode is suppressed. (0 References).
keywords:
Download | Details | Edit | Delete
title: UCLA-KIAE focusing permanent magnet undulator for SASE experiment
format: conference proceeding
conference: FEL 1997 19th
year: 1998
9 authors: Osmanov, N. | Tolmachev, S. | A. A. Varfolomeev | A. A. Varfolomeev | Pedro Frigola | M. Hogan | C. Pellegrini | R. Carr | Lidia, S.
abstract: A description of a new 2 m undulator is presented which was specially designed and manufactured for a SASE mode FEL experiment. It is a one section two plane focusing permanent magnet construction. The uniform period length is 2.06 cm, total number of periods is 98. The peak field on the axis is 5.4 kG for a 5 mm gap. (8 References).
keywords:
Download | Details | Edit | Delete
title: The VISA FEL Undulator
format: conference proceeding
conference: FEL 1998 20th
year: 1999
14 authors: R. Carr | I. Ben-Zvi | L. Bertolini | M. Cornacchia | P. Emma | Pedro Frigola | E. Johnson | M. Libkind | S. Lidia | H. D. Nuhn | C. Pellegrini | G. Rakowsky | J.B. Rosenzweig | R. Ruland
abstract: The Visible-Infrared SASE Amplifier (VISA) FEL is an experimental device designed to show self amplified spontaneous emission (SASE) to saturation in the 800-600 nm range, where silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is the first SASE FEL designed to saturate, and its diagnostics will provide important checks of theory.
keywords:
Download | Details | Edit | Delete
title: The Brookhaven Accelerator Test Facility
format: conference proceeding
conference: Linear Accelerator Conference 1988
year: 1989
15 authors: K. Batchelor | T. S. Chou | R. C. Fernow | J. Fischer | J. Gallardo | H. G. Kirk | R. Koul | R. B. Palmer | C. Pellegrini | J. Sheehan | T. Srinivasan-Rao | S. Ulc | M. Woodle | N. Kurnit | K. T. McDonald
abstract: The Brookhaven Accelerator Test Facility (ATF) will consist of a 50-100 MeV/c electron linac and a 100 GW CO/sub 2/ laser system. A high brightness RF-gun operating at 2856 MHz is to be used as the injector into the linac. The RF-gun contains a Nd:Yag-laser-driven photocathode capable of producing a stream of six ps electron pulses separated by 12.5 ns. The maximum charge in a micropulse will be one nano-Coulomb. The CO/sub 2/ laser pulse length will be a few picoseconds and will be synchronized with the electron pulse. The design electron beam parameters are given and possible initial experiments are discussed. (9 References).
keywords:
Download | Details | Edit | Delete
title: Influence of electron beam halos on the FEL performance
format: conference proceeding
conference: FEL 1998 20th
year: 1999
2 authors: B. Faatz | Sven Reiche
abstract: For single-pass free-electron lasers (FEL), such as amplifiers and SASE devices, saturation of the radiation power has to be reached within the length of the undulator. Therefore, detailed knowledge of electron beam parameters is crucial. So far, simulations have been performed with a given rms emittance and energy spread. At short radiation wavelengths, hunch compressors are used to compress the electron beam to achieve the desired high peak currents. In addition, external focusing along the entire undulator is used to maintain a constant small radius. The rotation of phase space due to compression might lead to a significant part of the bunch in tails that could increase the gain length. Furthermore, it is in general not possible to match both the beam core and the tail to the focusing structure. In this contribution, the influence of these tails, both transverse and in energy, on the FEL performance will be investigated. Simulations will be performed for beam parameters that have been assumed for the TESLA Test Facility FEL at DESY.
keywords:
Download | Details | Edit | Delete
title: Tunable two frequency free electron laser using a Pelletron as a driver for a plasma beatwave accelerator
format: conference proceeding
conference: FEL 1986 8th
year: 1987
4 authors: D. B. Cline | D. J. Larson | F. E. Mills | J.B. Rosenzweig
abstract: The possibility of amplifying two frequencies simultaneously in a free electron laser is discussed. Stability conditions for electron motion are derived, and numerical calculations reported. The advantages offered by using a DC Pelletron beam to power such a device, with application to the plasma beatwave accelerator-high efficiency, high average power, radiation wavelength tunability, and the possibility of phase locking several independent optical cavities-are evaluated. Related research efforts, and their impact on the design of this device, are discussed. (10 References).
keywords:
Download | Details | Edit | Delete
title: Electron-Positron Colliders in the TEV Region
format: conference proceeding
conference: International Symposium on Lepton and Photon Interactions at High Energies 1985
year: 1986
3 authors: G. Bonvicini | P. Gutierrez | C. Pellegrini
abstract: The authors review the main properties of e/sup +/e/sup -/ colliders, divided into 2 categories: storage rings and linear colliders; the basic physics, beam characteristics, limitations on beam current and density and their influence on the luminosity. (14 References).
keywords:
Download | Details | Edit | Delete
title: GENESIS 1.3: a fully 3D time-dependent FEL simulation code
format: conference proceeding
conference: FEL 1998 20th
year: 1999
1 author: Sven Reiche
abstract: Numerical simulation codes are basic tools for designing Free Electron Lasers (FEL). They are used to study the impact of different parameters, e.g. wiggler errors and external focusing, which allow FEL users to optimize the performance. For faster execution some simulation codes assume radial symmetry or decompose the radiation field into a few azimuthal modes, although then this treatment does not include the full description of the FEL. This contribution describes the new FEL code GENESIS 1.3 which uses a fully three-dimensional representation of the FEL equations in the paraxial approximation for time-dependent and steady-state simulations of single-pass FEL. In particular this approach is suitable for cases where the radial symmetry is broken by the electron beam distribution as well as by wiggler errors, betatron motion and off axis injection of the electron beam. The results, presented here, are based on the parameters of the TESLA Test Facility FEL at DESY.
keywords:
Download | Details | Edit | Delete
title: The Trieste synchrotron radiation project
format: conference proceeding
conference: National Conference on Synchrotron Radiation Instrumentation 5th
year: 1988
7 authors: M. Cornacchia | M. Campagna | L. Fonda | G. Magaritondo | C. Pellegrini | R. Rosei | C. Rubbia
abstract: The present the project for a superhigh brilliance soft X-ray source at Trieste. At present the project is fully funded and the conceptual design is being developed. The facility, scheduled to become operational in 1992, will deliver unprecedented levels of brilliance, and will be used for a variety of experiments in physics, chemistry, materials science, engineering, biology, technology, and medical research, involving scientists from Italy, from a number of European countries, and from the USA. (2 References).
keywords:
Download | Details | Edit | Delete
title: Remarks on the production of gravitational waves by EM radiation and particle beams
format: conference proceeding
conference: Workshop on Beam-Beam and Beam-Radiation Interactions: High Intensity and Nonlinear Effects
year: 1992
4 authors: Chen, P. | Diambrini-Palazzi, G. | K.J. Kim | C. Pellegrini
abstract: A report of the working group on the production of Gravitational Waves from electromagnetic radiation (EM) and particle beams. (9 References).
keywords:
Details | Edit | Delete
title: Ultrafast X-ray generation and applications using laser-linac interactions
format: conference proceeding
conference: IEEE LEOS Annual Meeting 1999
year: 1999
9 authors: T. Ditmire | T. E. Cowan | G. LeSage | M. Allen | G. Hays | K. B. Wharton | M. D. Perry | H. T. Powell | J.B. Rosenzweig
abstract: At LLNL we have been working to integrate an intense short-pulse laser with a low-emittance relativistic electron beam utilizing a 100 MeV S-band linac. This project uses a 100 TW, 35 fs laser, which is currently under development. (3 References).
keywords:
Download | Details | Edit | Delete
title: Summary Report: Working Group 3 on "Structure-Based Accelerator Concepts"
format: conference proceeding
conference: AAC 1997 7th
year: 1997
1 author: J.B. Rosenzweig
abstract: The working group on structure-based accelerators had an expansive mission, consisting of externally powered structures of high frequency, novel material and/or novel structure design, wakefield (excluding plasma) accelerators, and inverse radiative process accelerators. Within the context of these themes, discussions were held on the subjects of field gradient, efficiency, and accelerated beam quality, with an eye on technical and experimental issues brought on by the need to experimentally develop these schemes. We discuss here the progress presented in the working group, as well as recommendations for future directions in this area of advanced accelerator techniques.
keywords:
Download | Details | Edit | Delete
title: Experimental Measurement of Nonlinear Plasma Wake-Fields
format: conference proceeding
conference: PAC 1989
year: 1989
7 authors: J.B. Rosenzweig | Schoessow, P. | Cole, B. | W. Gai | Konecny, R. | Norem, J. | J. Simpson
abstract: We report direct high resolution observation of nonlinear steepened plasma waves excited in the wake of an intense, self-pinched electron beam. Oscillations in both accelerating and deflecting fields are measured, and analyzed in the context of linear and nonlinear plasma wave theory. The degree of nonlinearity in the wake-fields is shown to be consistent with analytical predictions of the beam self-pinching. The impact of these results on plasma acceleration and focusing schrmrs is discussed.
keywords:
Download | Details | Edit | Delete
title: Enhanced resistive wall instability for off-centred beams
format: conference proceeding
conference: PAC 1979
year: 1979
4 authors: E.D. Courant | M. Month | C. Pellegrini | J.M. Wang
abstract: Beam occupation of a large fraction of the available vacuum chamber typical of high energy proton storage ring designs, results in an enhancement of the resistive wall instability. The effect is considered for ISABELLE during the current stacking procedure. Results for the coasting stack in its initial phase as well as for the injected bunches are presented. (4 References).
keywords:
Download | Details | Edit | Delete
title: An Optimized Slab-Symmetric Dielectric-Based Laser Accelerator Structure
format: conference proceeding
conference: AAC 1998 8th
year: 1999
2 authors: J.B. Rosenzweig | Schoessow, P.
abstract: A slab-symmetric, partially dielectric filled, laser excited structure which may be used to accelerate charged particles is analyzed theoretically and computationally. The fields associated with the accelerating mode are calculated, as are aspects of the resonant filling and impedance matching of the structure to the exciting laser. It is shown through computer simulation that the accelerating mode in this structure can be excited resonantly and with large quality factor Q. Practical aspects of implementing this structure as an accelerator are discussed. (7 References).
keywords:
Download | Details | Edit | Delete
title: Operational status of the Brookhaven National Laboratory Accelerator Test Facility
format: conference proceeding
conference: PAC 1989
year: 1989
18 authors: Batchelor, K. | Ben-Zvi, I. | Biglio, I. | Chou, T. S. | R. Fernow | Fischer, J. | J. Gallardo | H. G. Kirk | Kurnit, N. | McDonald, K. T. | Palmer, R. B. | Parsa, Z. | C. Pellegrini | Sheehan, J. | Srinivasan-Rao, T. | Ulc, S. | M. Woodle | van Steenbergen, A.
abstract: The design and operation of a 50-MeV electron linear accelerator utilizing a low emittance ( gamma epsilon =5 to 10 mm-mrad) radio-frequency gun operating at an output energy of 5 MeV and a charge of 1 nC are described. Design calculations, early radio-frequency measurements, and operational experience with the electron gun utilizing a dummy cathode in place of the proposed photocathode emitter are given. The dynamics of the electron beam coming off the photocathode has been modeled with the programs PARMELA and MASK. General agreement as to the expected characteristics of the electron beam at the RF-gun exit has been obtained using the two programs. It was also verified that, with proper matching of the transverse beam, no increase of the transverse normalized emittance occurs at the linac due to the fundamental RF mode. (5 References).
keywords:
Download | Details | Edit | Delete
title: The UCLA infrared free-electron laser
format: conference proceeding
conference: SPIE Conference on Intense Laser Beams
year: 1992
17 authors: J. W. Dodd | S. C. Hartman | S. Park | C. Pellegrini | J.B. Rosenzweig | J. A. Smolin | W. A. Barletta | D.B. Cline | R. K. Copper | J. Kolonko | J. G. Davis | G. Hairapetian | C. J. Joshi | N. C. Luhmann | S. N. Ivanchenkov | A. S. Khlebnikov | A. A. Varfolomeev
abstract: A compact 20 MeV linac with an RF laser-driven electron gun will drive a high-gain (10 cm gain length), 10.6 mu m wavelength FEL amplifier, operating in the SASE mode. FEL physics in the high-gain regime will be studied, including start-up from noise, optical guiding, sidebands, saturation, and superradiance, with emphasis on the effects important for future short wavelength operation of FELs. The hybrid undulator, designed and built at the Kurchatov Institute of Atomic Energy in the USSR has forty periods, each 1.5 cm long, the magnetic material is a hybrid combination of SmCo_5 blocks and Nd-Fe-B blocks, with vanadium-permendur yokes. The gap distance between pole-tips is fixed at 5 mm. On axis the peak value of the completed undulator's magnetic field was measured to be 7.3 kGauss (+/- 0.25%). Measurements during the conditioning phase of the RF gun for the electron beam's peak dark-current show 6 mA without the longitudinal magnetic focusing field in the gun and 34 mA with the focusing field active. The peak current from photoemission is calculated to be 200 A.
keywords:
Download | Details | Edit | Delete
title: Synchronization of sub-picosecond electron and laser pulses
format: conference proceeding
conference: AAC 1998 8th
year: 1999
2 authors: J.B. Rosenzweig | G.P. Le Sage
abstract: Pulse-compression techniques apply a longitudinal restoring force which improves synchronization between electron bunches and the RF drive, partially or completely correcting errors in the exit time from the injector. While this feature is beneficial in terms of linac related phase matching issues and jitter in the photocathode laser system, laser jitter with respect to the RF clock is in fact worsened in terms of the final interaction of laser and electron pulses. That is, if one attempts to synchronize the electron bunch to an external laser, deriving external laser timing from, say, the photocathode drive laser oscillator, the relative timing of electron and the external laser will be mismatched, because the electron beam is pulled toward a given phase of the RF clock. Thus, if one wishes to take advantage of the locking of the electron beam to the (assumed stable) RF clock, then an equivalent mechanism must be found for locking the external laser to the RF clock as well.
keywords:
Download | Details | Edit | Delete
title: Beam break-up in the two-beam accelerator
format: conference proceeding
conference: PAC 1989
year: 1989
5 authors: D. H. Whittum | G. Travish | Sessler, A. M. | G. D. Craig | J. F. DeFord
abstract: Beam breakup (BBU) in the drive beam of a two-beam accelerator (TBA) using transverse wakes calculated by the AMOS code was studied numerically. Only cumulative BBU due to the wake of the linear induction accelerator cavities is considered. Growth lengths on the order of approximately 100 m are found for typical parameters. It is concluded that these growth lengths are acceptable for a future TBA. (14 References).
keywords:
Download | Details | Edit | Delete
title: Wiggler, undulator and free electron laser radiation sources development at the National Synchrotron Light Source
format: conference proceeding
conference: International Conference on X-Ray and VUV Synchrotron Radiation Instrumentation
year: 1983
5 authors: H. Hsieh | S. Krinsky | A. Luccio | C. Pellegrini | A. van Steenbergen
abstract: An overview is presented of the special radiation sources development at the NSLS for incorporation in a 2.5 GeV X-ray storage ring and a 700 MeV VUV storage ring. This includes a superconducting high field multipole wiggler, lambda /sub c/=0.5 AA; a permanent magnet wiggler, lambda /sub c/=2.0 AA; a maximum photon energy undulator (5-7 keV); an undulator for a soft X-ray line or 'continuum' spectrum and a free electron laser source tunable in the 2500-4500 AA region. Source characteristics and status of development are given. In addition, the incorporation of a backscattered Compton photon source is being studied and relevant parameters are presented. (22 References).
keywords:
Download | Details | Edit | Delete
title: Initial operation of the UCLA plane wave transformer (PWT) linac
format: conference proceeding
conference: PAC 1995
year: 1995
10 authors: R. Zhang | P. Davis | G. Hairapetian | M. Hogan | C. Joshi | M. Lampel | S. Park | C. Pellegrini | J.B. Rosenzweig | G. Travish
abstract: We report on the initial operation of a novel compact rf linac-the plane wave transformer (PWT). The PWT is a 42 cm long, 8 cell standing-wave structure, operated at S-band, in a pi -mode. We present the properties of this linac at rf power levels from 4 MW to 8 MW and beam energy from 7 MeV to 10 MeV, measured initially using both dark current and photo-electrons. Some technical issues associated with the operation are discussed. Future improvements of the PWT, using a modified design, are also studied. (6 References).
keywords:
Download | Details | Edit | Delete
title: Coherent transition radiation-based diagnosis of electron beam pulse shape
format: conference proceeding
conference: AAC 1998 8th
year: 1999
3 authors: J.B. Rosenzweig | A. Murokh | A. Tremaine
abstract: The bunch shapes of an electron beams is increasingly difficult to measure, as the time-scales of interest are now sub-picosecond. We discuss here the use of coherent transition radiation (CTR) for such measurements. Two types of measurements are presented: the deduction of macroscopic (0.3 psec resolution) pulse profile using interferometry, and the examination of microbunch (50 fsec) structure from an FEL-bunched beam using spectral characteristics of the CTR. For the macrobunch measurement we discuss the problem of missing low frequency radiation and one solution for extracting meaningful data with this problem are presented. For microbunch CTR, we examining initial spectrally-resolved measurements, and some interesting deviations in the CTR spectrum from the standard theoretical predictions. (23 References).
keywords:
Download | Details | Edit | Delete
title: Report on the Lake Arrowhead workshop on advanced acceleration concepts
format: conference proceeding
conference: PAC 1989
year: 1989
1 author: C. Pellegrini
abstract: The author reviews the present status of the field of new acceleration concepts, as presented at the Lake Arrowhead workshop, held at the beginning of 1989. It is pointed out that the field of advanced accelerator concepts has seen a remarkable progress during the last few years. Plasma and wakefield acceleration has been demonstrated. One can foresee similar progress in the area of laser acceleration when the Brookhaven ATF starts operation. Ideas for using plasmas to focus particle beams and to produce beam neutralization at the interaction point of a collider have also been developed. It is further noted that the development of high-brightness beams and high-gradient linacs can also have, in the near future, a strong impact on other fields, such as FELs (free-electron lasers) and synchrotron radiation sources. (43 References).
keywords:
Download | Details | Edit | Delete
title: Optimization of the parameters of a storage ring for a high power XUV free electron laser
format: conference proceeding
conference: International Conference on Insertion Devices for Synchrotron Sources
year: 1986
12 authors: A. Jackson | J. Bisognano | S. Chattopadhyay | M. Cornacchia | A. Garren | K. Halbach | K.J. Kim | H. Lancaster | J. Peterson | M. S. Zisman | C. Pellegrini | G. Vignola
abstract: The authors describe the operation of an XUV high gain FEL operating within a bypass of an electron storage ring, and discuss the implications on storage ring optimization imposed be FEL requirements. It transpires that, in the parameter regime of interest, collective effects within the beam play an important role. For example, intrabeam scattering dilutes the transverse emittance of the beam and the microwave instability increases the momentum spread. Both phenomena reduce the effectiveness of the FEL. A computer code, ZAP, has been written which, for a given lattice design, takes all such effects into consideration and produces a figure of merit for FEL operation for that machine. They show the results of ZAP for several storage ring designs, all optimized for FEL operation, and present a design example of a facility capable of producing coherent radiation at 400 AA with tens of megawatts of peak power. (24 References).
keywords:
Download | Details | Edit | Delete
title: Wakefields In Planar Dielectric-Loaded Structures
format: conference proceeding
conference: Summer Study on New Directions for High Energy Physics
year: 1997
4 authors: A. Tremaine | J.B. Rosenzweig | Schoessow, P. | W. Gai
abstract: Several promising schemes for high-gradient acceleration of charged particles in planar electromagnetic structures have been recently proposed. In this paper we investigate, by both computer simulation and theoretical analysis, the longitudinal and transverse wake-fields experienced a relativistic charged particle in a planar structure. We show that, in the limit of a large aspect ratio beam, the net deflecting wake-fields vanishes. Practical implications of this result for short wavelength advanced accelerators are discussed.
keywords:
Download | Details | Edit | Delete
title: Test results of the plasma source for underdense plasma lens experiments at the UCLA Neptune Lab
format: conference proceeding
conference: AAC 1998 8th
year: 1999
7 authors: Suk, H. | C. E. Clayton | R. Narang | P. Muggli | J.B. Rosenzweig | C. Pellegrini | C. Joshi
abstract: A plasma source was developed at UCLA for planned underdense plasma lens experiments, where the plasma density is less than the electron beam density. The argon plasma, produced by a discharge between a LaB_6 cathode at 1330 degrees C and a tantalum anode, is confined by a solenoidal magnetic field and flows transversely across the electron beam path. Extensive test of the plasma source is under way for various conditions before it is assembled with the UCLA photocathode-based electron linac. In particular, different longitudinal (with respect to the electron beam) plasma profiles and effective plasma lengths can be obtained by adjusting the moveable sliding door between the plasma source and the transverse beamline. Test results of the plasma source are presented. (11 References).
keywords:
Download | Details | Edit | Delete
title: The Brookhaven Accelerator Test Facility injection system
format: conference proceeding
conference: PAC 1989
year: 1989
5 authors: X.J. Wang | H. G. Kirk | C. Pellegrini | McDonald, K. T. | Russell, D. P.
abstract: The Brookhaven Accelerator Test Facility (ATF) consists of a 50-MeV/c electron linac and a high-brightness RF gun, both operating at 2856 MHz. An extremely short (a few picoseconds) electron pulse with a low transverse emittance is generated by the RF gun. In order to preserve both longitudinal and transverse emittances, great care must be taken in transporting the electron beam from the RF gun to the linac. The injection line is described, first- and second-order lattice studies of the injection line are presented, and nonlinear effects on the emittance are studied. It is shown that it is possible to preserve transverse emittance in a low-energy beam-transfer line by use of slits and contoured edges of the dipole magnets. Bunch lengthening is induced by the large beam divergence out of the RF gun, thus requiring strong focusing. (11 References).
keywords:
Download | Details | Edit | Delete
title: Collective instabilities and high-gain regime free electron laser
format: conference proceeding
conference: Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation
year: 1984
3 authors: R. Bonifacio | C. Pellegrini | L. M. Narducci
abstract: Studies the conditions for collective instability of the electron beam-undulator-radiation field of free electron lasers. The authors derive the characteristic complex frequencies of the FEL. From this result, the small-signal gain formula is obtained. They consider the problem of the initiation of laser action and growth of the radiation field from noise. The nonlinear regime is studied numerically. (14 References).
keywords:
Download | Details | Edit | Delete
title: Measurements of the tune variations induced by non-linearities in lepton machines
format: conference proceeding
conference: EPAC 1996
year: 1997
9 authors: Bartolini, R. | Giovannozzi, M. | Scandale, W. | Verdier, A. | C. Pellegrini | Tran, P. | Todesco, E. | Corbett, J. | M. Cornacchia
abstract: The precise measurement of the betatron tune as a function of the oscillation amplitude provides a useful information on non-linear beam dynamics. In lepton accelerators, this measurement is made difficult due to various damping mechanism. To counteract this, we propose to use algorithms that provide a precise measurement of the tune in a small number of turns. We apply these procedures in LEP at injection and collision energy, as well as in SPEAR at injection energy. Collections of experimental data, and a first comparison with the results of model-based simulations are discussed. (9 References).
keywords:
Download | Details | Edit | Delete
title: A high energy proton-electron-positron colliding beam system
format: conference proceeding
conference: HEACC 1971 8th
year: 1971
6 authors: C. Pellegrini | J. Rees | B. Richter | M. Schwartz | D. Mohl | A. M. Sessler
abstract: A system of two intersecting storage tings of gross radius 260 m, one for protons and the other for electrons and positrons, is described. The maximum energy of the stored proton beam is 70 GeV, that of the electron and positron beams 15 GeV; so the center-of-mass energies are 65 GeV for e-p collisions and 30 GeV for e/sup +/-e/sup -/ collisions. The performance of the system is determined by the RF power available for the electron and positron brams and by the incoherent beam-beam limit on transverse beam density. With an available RF power for the beams of 2.7 MW, the system yields design luminosities in the vicinity of 10/sup 32/ cm/sup -2/ sec/sup -1/ in both modes of operation. Some important physics experiments and their yields are discussed.
keywords:
Download | Details | Edit | Delete
title: Instability of compensated beam-beam collisions
format: conference proceeding
conference: AAC 1989
year: 1989
2 authors: J.B. Rosenzweig | B. Autin
abstract: The beam-beam disruption phenomena in linear colliders are increasingly seen as a source of serious problems for these machines. The maximum disruption-induced angle introduces a constraint on final focusing system apertures, which has led to the complication of interaction point crossing angles. Additional constraints arise due to the desire to minimize the energy spread due to beamstrahlung energy loss to acceptable levels. Much more seriously, the beamstrahlung photons produced during disruption have been shown to pair-produce via interaction with the opposing bunch's disruption fields. (11 References).
keywords:
Download | Details | Edit | Delete
title: High-gain free electron lasers as generators of short wavelength coherent radiation
format: conference proceeding
conference: Conference on Short Wavelength Coherent Radiation: Generation and Applications
year: 1986
2 authors: K.J. Kim | C. Pellegrini
abstract: The development of coherent radiation in high-gain free electron lasers, either from initial noise or from low-power input radiation, is analyzed in terms of three-dimensional Maxwell-Klimontovich equations. Exponential growth and saturation, transverse radiation profiles, transverse coherence and spectral features are discussed. Two possible systems of high-gain free electron lasers, one based on a storage ring and by-pass, another based on a linac and damping ring, are considered for the generation of 400 AA radiation. (19 References).
keywords:
Download | Details | Edit | Delete
title: The transverse optical klystron experiment at NSLS: laser harmonics into the XUV
format: conference proceeding
conference: Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation
year: 1984
7 authors: B.M. Kincaid | R. R. Freeman | C. Pellegrini | A. Luccio | S. Krinsky | A. van Steenbergen | F. DeMartini
abstract: Describes the theory of the production of coherent XUV and soft X-rays using a transverse optical klystron (TOK). A TOK uses a high powered laser in conjunction with an undulator magnet to produce laser-like output of XUV radiation from the relativistic stored electron beam in the NSLS VUV electron storage ring. (13 References).
keywords:
Download | Details | Edit | Delete
title: Envelope description of quasi-laminar beams undergoing reversible emittance transformations
format: conference proceeding
conference: EPAC 1996
year: 1997
2 authors: L. Serafini | J.B. Rosenzweig
abstract: A fully analytical description is presented for the envelope behavior of intense, space charge dominated beams which are relativistic and quasi-laminar. It is based on a particular solution of the envelope equation for an accelerated beam, which is invariant under reversible emittance transformations: this solution has been termed invariant envelope. The treatment presented in this paper is applicable both to bunched beams in transport lines and in linacs, whenever the beam is space charge dominated. The main interest is in maximizing the beam brightness achievable by Photo-Injectors and preserving the beam quality during the first stages of acceleration. Simple analytical formulae are provided to predict the performances of these devices, when they are operated in the space charge emittance correction regime. (7 References).
keywords:
Download | Details | Edit | Delete
title: Argonne plasma wake-field acceleration experiments
format: conference proceeding
conference: AAC 1989
year: 1989
7 authors: J.B. Rosenzweig | B. Cole | W. Gai | R. Konecny | J. Norem | P. Schoessow | J. Simpson
abstract: Four years after the initial proposal of the Plasma Wake-field Accelerator (PWFA), it continues to be the object of much investigation, due to the promise of the ultra-high accelerating gradients that can exist in relativistic plasma waves driven in the wake of charged particle beams. These wake-fields are of interest both in the laboratory, for acceleration and focusing of electrons and positrons in future linear colliders, and in nature as a possible cosmic ray acceleration mechanism. The authors review the recent experimental advances made in PWFA research at Argonne National Laboratory. (25 References).
keywords:
Download | Details | Edit | Delete
title: Tunable two frequency free electron laser using a Pelletron as a driver for a plasma beatwave accelerator
format: conference proceeding
conference: High Intensity Laser Processes
year: 1986
4 authors: D.J. Larson | J.B. Rosenzweig | D.B. Cline | F.E. Mills
abstract: The possibility of amplifying two frequencies simultaneously in a free electron laser is discussed. Stability conditions for electron motion are derived, and numerical calculations reported. The advantages offered by using a DC Pelletron beam to power such a device, with application to the plasma beatwave accelerator-high efficiency, high average power, radiation wavelength tunability, and the possibility of phase locking several independent optical cavities-are evaluated. Related research efforts, and their impact on the design of this device are discussed. (10 References).
keywords:
Download | Details | Edit | Delete
title: A plasma klystron for generating ultra-short electron bunches
format: conference proceeding
conference: Workshop on Second Generation Plasma Accelerators
year: 1996
7 authors: T.C. Katsouleas | C. E. Clayton | L. Serafini | C. Pellegrini | C. Joshi | Dawson, J. | Castellano, P.
abstract: A technique for producing ultra-short electron bunches (e,g., less than or equal to 100 fs) from a continuous electron beam using a short plasma wave section and a drift space is explored. The bunches are a fraction of a plasma wavelength long and are spaced by a plasma wavelength, making them of interest for injection into plasma accelerators or for driving a klystron-like structure to produce infrared radiation.
keywords:
Download | Details | Edit | Delete
title: Experimental testing of the TTF RF photoinjector
format: conference proceeding
conference: PAC 1997
year: 1998
7 authors: E. Colby | M. Conde | J.B. Rosenzweig | P. Colestock | H. Edwards | Koepke, K. P. | Nezrick, F.
abstract: Results from the experimental testing of the prototype TESLA Test Facility (TTF) RF photoinjector are summarized. Preliminary measurements of the performance of the injector indicate that, with refinement, the design values for the transverse emittances (20 x 20 pi mm-mr) are not unrealistic, with uncompressed transverse emittances of 40 pi mm mr having been obtained under somewhat less ideal circumstances than those simulated. Preliminary pulse length measurements with and without the pulse compressor suggest pulse compression, but further study is required.
keywords:
Download | Details | Edit | Delete
title: A Numerical Method of Calculating the Effective Start-Up Power in a High Gain Free Electron Laser
format: conference proceeding
conference: FEL 1986 8th
year: 1997
2 authors: M. Hogan | G. Travish
abstract: We present a simple model of the startup process in a high gain Free Electron Laser (FEL). The model is used to numerically calculate the power generated within the first gain length of the FEL, which is amplified by the remainder of the undulator. The model takes into account the bandwidth and angular limits imposed by the high-gain process. A brief comparison of the results of this model to an analytic approximation for calculating the start-up power is also given.
keywords:
Details | Edit | Delete
title: Photocathode driven linac at UCLA for FEL and plasma wakefield acceleration experiments
format: conference proceeding
conference: PAC 1991
year: 1991
17 authors: S. Hartman | F. Aghamir | W. Barletta | D. B. Cline | J. Dodd | T. Katsouleas | J. Kolonko | S. Park | C. Pellegrini | J.B. Rosenzweig | Smolin, J. A. | Terrien, C. | J. Davis | G. Hairapetian | C. Joshi | N. Luhmann | D. McDermott
abstract: The UCLA compact 20-MeV/c electron linear accelerators is designed to produce a single electron bunch with a peak current of 200 A, an RMS energy spread of 0.2% or less, and a short 1.2-ps RMS pulse duration. The linac is also designed to minimize emittance growth down the beamline so as to obtain emittances on the order of 8 pi mm-mrad in the experimental region. The linac will feed two beamlines, the first will run straight into the undulator for FEL experiments while the second will be used for diagnostics, longitudinal bunch compression and other electron beam experiments. A description is given of the considerations that went into the design of the accelerating structures and the transport to the experimental areas. (8 References).
keywords:
Download | Details | Edit | Delete
title: The FEL development at the Advanced Photon Source
format: conference proceeding
conference: Free-Electron Laser Challenges II
year: 1999
4 authors: S. V. Milton | N. D. Arnold | C. Benson | S. Berg
abstract: Construction of a single-pass free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) mode of operation is nearing completion at the Advanced Photon Source (APS) with initial experiments imminent. The APS SASE FEL is a proof-of-principle fourth-generation light source. As of January 1999 the undulator hall, end-station building, necessary transfer lines, electron and optical diagnostics, injectors, and initial undulators have been constructed and, with the exception of the undulators, installed. All preliminary code development and simulations have also been completed. The undulator hall is now ready to accept first beam for characterization of the output radiation. It is the project goal to push towards full FEL saturation, initially in the visible, but ultimately to UV and VUV, wavelengths. (10 References).
keywords:
Download | Details | Edit | Delete
title: Pulse compression in radio frequency photoinjectors: applications to advanced accelerators
format: conference proceeding
conference: Workshop on Second Generation Plasma Accelerators
year: 1996
3 authors: J.B. Rosenzweig | N. Barov | E. Colby
abstract: While RF photoinjectors are an excellent source of high brightness electron beams, there are constraints to tying together the expected emittance and peak current performance of a given photoinjector system. These constraints, which arise from the complicated dynamics of the electrons due to the interplay of RF and space-charge forces within the photoinjector, tend to favor lower peak current operation. For some ultimate uses of photoinjector beams, such as linear collider test beams, wakefield accelerators, and free-electron lasers (FEL's), one may desire much higher peak currents. In this case, an inexpensive and reliable method for producing extremely short high-current electron bunches is to use magnetic compression. We examine this scheme analytically and by computer simulation. Many applications are illustrated, including the TESLA Test Facility/FEL injector, ultra-high current beams for plasma wakefields and generation of femtosecond electron pulses for injection ultra-high current beams for injection into short wavelength laser-based accelerators. It is shown that the injection timing jitter associated with the laser can be nearly eliminated using this scheme, making it an indispensable component in many of the advanced accelerator injectors we consider.
keywords:
Download | Details | Edit | Delete
title: The NEPTUNE facility for 2nd generation advanced accelerator experiments
format: conference proceeding
conference: PAC 1997
year: 1998
5 authors: C. E. Clayton | C. Joshi | K. A. Marsh | C. Pellegrini | J.B. Rosenzweig
abstract: The NEPTUNE Laboratory, under construction at UCLA, will be a user facility for exploring concepts useful for advanced accelerators. [1] The programmatic goal for the laboratory is to inject extremely high quality electron bunches into a laser-driven plasma beat wave accelerator (PBWA) [2] and explore ideas for extracting a high quality DE/E < 0.1, epsilon_n < 10 pi mm-mrad), high energy (100 MeV) beam from a plasma structure operating at about 1 THz and about 3 GeV/m. The lab will combine an upgraded MARS CO2 laser and the state-of-the-art SATURNUS RF gun and linac. [3] The new MARS laser will be about 1 TW (100 J, 100 ps), up from 0.2 TW (70 J, 350 ps). This allows for doubling the spot size at the IP and quadrupling the interaction length while still driving gradients of 3 GeV/m. The SATURNUS gun will be upgraded to the Brookhaven 1.6 cell design. [4] A novel, multi-cell Plane-Wave Transformer (PWT) RF gun is also under development. [5] A sync-pumped, sub-ps dye laser is available to directly produce ultrashort electron pulses (1/5 of an accelerating bucket). Part of the research program will be devoted to studying pulse compression [6] and phaselocking techniques at these ultrahigh frequencies and diagnosing microbunches generated by such structures. [7] Finally, shaped electron pulses will be studied for the electron driven Plasma Wakefield Accelerator (PWFA) concept.
keywords:
Download | Details | Edit | Delete
title: Commissioning and measurements of the Neptune photo-injector
format: conference proceeding
conference: AAC 2000 9th
year: 2001
6 authors: S. Anderson | Loh, M. | P. Musumeci | J.B. Rosenzweig | Suk, H. | M.C. Thompson
abstract: The photo-injector for the Neptune Advanced Accelerator Laboratory is introduced. Its component parts, including the radio frequency gun, photo-cathode drive laser system, booster linac, RF system, chicane compressor, beam diagnostics, and control system are described. The injector is designed to produce high brightness, short pulse electron beams. Measurements of the photo-injector beams including quantum efficiency, emittance, pulse length, and pulse compression are presented. (21 References).
keywords:
Download | Details | Edit | Delete
title: Coherent X-rays from PEP
format: conference proceeding
conference: PAC 1991
year: 1991
7 authors: S. Baird | Nuhn, H. D. | R. Tatchyn | H. Winick | A.S. Fisher | J.C. Gallardo | C. Pellegrini
abstract: The authors explore the use of a large-circumference, high-energy electron-positron collider such as PEP to drive a free-electron laser (FEL), producing high levels of coherent power at short wavelengths. They consider self-amplified spontaneous emission (SASE), in which electron bunches with low emittance, high peak current, and small energy spread radiate coherently in a single pass through a long undulator. The authors also explore various combinations of electron-beam and undulator parameters, as well as special undulator designs and optical klystrons (OKs), to reach high average or peak coherent power at wavelength around 40 AA by achieving significant exponential gain or full saturation. Examples are presented for devices that achieve high peak coherent power (up to about 400 MW) with lower average coherent power (about 20 mW) and other devices which produce a few watts of average coherent power. (22 References).
keywords:
Download | Details | Edit | Delete
title: Measurements of high gain and noise fluctuations in a SASE free electron laser
format: conference proceeding
conference: Workshop on Single Pass, High Gain FELs Starting from Noise Aiming at Coherent X-Rays
year: 1997
12 authors: M. Hogan | S. Anderson | K. Bishofberger | Pedro Frigola | A. Murokh | N. Osmanov | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | G. Travish | A. Tremaine | A. A. Varfolomeev
abstract: We report measurements of large gain for a single pass Free Electron Laser operating in Self Amplified Spontaneous Emission (SASE) at 16 mu m starting from noise. We also report the first observation and analysis of intensity fluctuations of the SASE radiation intensity in the high gain regime. The results are compared with theoretical predictions and simulations. (11 References).
keywords:
Download | Details | Edit | Delete
title: RF photoinjector development for a short-pulse, hard X-ray Thomson scattering source
format: conference proceeding
conference: AAC 2000 9th
year: 2001
6 authors: G.P. Le Sage | S. G. Anderson | T. E. Cowan | J. K. Crane | T. Ditmire | J.B. Rosenzweig
abstract: An important motivation in the development of the next generation X-ray light sources is to achieve picosecond and sub-ps pulses of hard X-rays for dynamic studies of a variety of physical, chemical anti biological processes. Present hard X-ray sources are either pulse-width or intensity limited, which allows ps-scale temporal resolution only for signal averaging of highly repetitive processes. A much faster and brighter hard X-ray source is being developed at LLNL, based on Thomson scattering of fs-laser pulses by a relativistic electron beam, which will enable X-ray characterization of the transient structure of a sample in a single shot. Experimental and diagnostic techniques relevant to the development of next generation sources including the Linac Coherent Light Source can be tested with the Thomson scattering hard X-ray source. This source will combine an RF photoinjector with a 100 MeV S-band linac. The photoinjector and linac also provide an ideal test-bed for examining space-charge induced emittance growth effects. A program of beam dynamics and diagnostic experiments are planned in parallel with Thomson source development. Our experimental progress and future plans will be discussed.
keywords:
Download | Details | Edit | Delete
title: RF AND MAGNETIC MEASUREMENTS ON THE SPARC PHOTOINJECTOR AND SOLENOID AT UCLA
format: conference proceeding
conference: PAC 2005
year: 2005
8 authors: J.B. Rosenzweig | A.M. Cook | M.P. Dunning | P. Frigola | G. Travish | C. Sanelli | F. Tazzioli | D. T. Palmer
abstract: The rf photocathode gun and the solenoid for the SPARC project at INFN-LNF (Frascati) have been fabricated and undergone initial testing at UCLA. The advanced aspects of the design of these devices are detailed. Final diagnosis of the tuning of the RF gun performance, including operating mode frequency and field balance, is described. The emittance compensating solenoid magnet, which is designed to be tuned in longitudinal position by differential excitation of the coils, has been measured using Hall probe scans for field profiling, and pulsed wire methods to determine the field center. Comparisons between measurements and the predictions of design codes are made.
keywords:
Download | Details | Edit | Delete
title: Numerical study of X-ray FELs including quantum fluctuation
format: conference proceeding
conference: Workshop on Single Pass, High Gain FELs Starting from Noise Aiming at Coherent X-Rays
year: 1997
4 authors: Sven Reiche | E. L. Saldin | E. A. Schneidmiller | M. V. Yurkov
abstract: One of the fundamental limitations towards achieving very short wavelength in a self amplified spontaneous emission free electron laser (SASE FEL) is connected with the energy diffusion in the electron beam due to quantum fluctuations of undulator radiation. Parameters of the LCLS and TESLA X-ray FEL projects are very close to this limit and there exists necessity in upgrading FEL simulation codes for optimization of SASE FEL for operation at a shortest possible wavelength. In this report we describe a one-dimensional FEL simulation code taking into account the effects of incoherent undulator radiation. Using similarity techniques we have calculated universal functions describing degradation of the FEL process due to quantum fluctuations of undulator radiation.
keywords:
Download | Details | Edit | Delete
title: A high current superconducting proton linac for an accelerator driven transmutation system
format: conference proceeding
conference: PAC 1997
year: 1998
7 authors: C. Pagani | G. Bellomo | P. Pierini | G. Travish | D. Barni | A. Bosotti | R. Parodi
abstract: High current CW proton linac accelerators have been recently proposed for a number of applications based on the use of a large flux of spallation neutrons. In this context, an R&D program on an accelerator driven system for nuclear waste transmutation has been recently approved in Italy. Our specific task is to develop, together with the national industry, a design of the high energy part of the proton accelerator, along with prototype development for the most critical components. In this paper we present a revised version of the design proposed at Linac'96, using five cell cavities, rather than the original four cells. This modification, together with a new criterion for using the transit time factor curve for non resonant proton velocities, results in a more modular and efficient design. A 1.6 GeV linac, operated at 25 mA, allows to reach 40 MW beam power. The beam power upgrade is achievable using additional couplers per cavity. (5 References).
keywords:
Download | Details | Edit | Delete
title: IFEL experiment at the Neptune Lab
format: conference proceeding
conference: AAC 2000 9th
year: 2001
2 authors: P. Musumeci | C. Pellegrini
abstract: We present a two stage Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Lab. Proof-of-principle experiments on the IFEL scheme have been carried out successfully. This experiment is intended to achieve a 100 MeV energy gain, staging two IFEL modules. It will use a 16 MeV electron beam, a 1 TW CO/sub 2/ laser and two different tapered helical undulators. The problem of refocusing both laser and electron beam is analyzed in detail. A preliminary beam-line layout and numerical simulation are presented. (11 References).
keywords:
Download | Details | Edit | Delete
title: Plasma Lenses for SLAC Final Focus Test Facility
format: conference proceeding
conference: PAC 1991
year: 1991
11 authors: D. Betz | Chen, P. | D. B. Cline | Gundersen, M. | C. Joshi | T. Katsouleas | Norem, J. | Rajagopalan, S. | J.B. Rosenzweig | Su, J. J. | Williams, R.
abstract: A collaborative group of accelerator and plasma physicists and engineers has formed with an interest in exploring the use of plasma lenses to meet the needs of future colliders. Analytic and computational models of plasma lenses are briefly reviewed and several design examples for the SLAC Final Focus Test Beam are presented. The examples include discrete, thick, and adiabatic lenses. A potential plasma source with desirable lens characteristics is presented.
keywords:
Download | Details | Edit | Delete
title: Where do we stand with high gain FEL simulations?
format: conference proceeding
conference: Workshop on Single Pass, High Gain FELs Starting from Noise Aiming at Coherent X-Rays
year: 1997
1 author: G. Travish
abstract: Computer technology improvements have allowed for more complete and detailed free electron laser simulations, yet the demands of the large number of new experiments and proposed projects has outpaced the capability and availability of present codes. The paper, based on a talk given at the conference of these proceedings, presents a brief assessment of Free Electron Laser (FEL) codes, their availability and features, as well as some opinions on what direction the FEL code community should take for the near future. The discussion of FEL codes is restricted here to ones for high gain amplifiers: no codes for oscillators, waveguides or exotic configurations are considered. (6 References).
keywords:
Download | Details | Edit | Delete
title: Emittance Studies of the BNL/SLAC/UCLA 1.6 Cell Photocathode RF Gun
format: conference proceeding
conference: PAC 1997
year: 1998
11 authors: D. T. Palmer | X. J. Wang | R. H. Miller | M. Babzien | I. Ben-Zvi | C. Pellegrini | Sheehan, J. | Skaritka, J. | H. Winick | M. Woodle | V. Yakimenko
abstract: The symmetrized 1.6 cell S-band photocathode gun developed by the BNL/SLAC/UCLA collaboration is in operation at the Brookhaven Accelerator Test Facility (ATF). A novel emittance compensation solenoid magnet has also been designed, built and is in operation at the ATF. These two subsystems form an emittance compensated photoinjector used for beam dynamics, advanced acceleration and free electron laser experiments at the ATF. The highest acceleration field achieved on the copper cathode is 150 MV/m, and the guns normal operating field is 130 MV/m. The maximum rf pulse length is 3 mu s. The transverse emittance of the photoelectron beam were measured for various injection parameters. The 1 nC emittance results are presented along with electron bunch length measurements that indicated that at above the 400 pC, space charge bunch lengthening is occurring. The thermal emittance, epsilon_0, of the copper cathode has been measured. (7 References).
keywords:
Download | Details | Edit | Delete
title: Beam dynamics in an integrated plane wave transformer photoinjector at S and X-band
format: conference proceeding
conference: PAC 1997
year: 1998
6 authors: J.B. Rosenzweig | X. Ding | D. T. Palmer | C. Pellegrini | L. Serafini | D. Yu
abstract: The beam dynamics of an integrated S-band RF photoinjector based on the plane wave transformer (PWT) concept, proposed as part of an SBIR collaboration between UCLA and DULY Research, are studied. The design, which calls for an 11.5 cell structure run at a peak accelerating field of 60 MV/m and uses a compact solenoid around the initial 2.5 cells, is based on a recently developed theory of emittance compensation. It calls for matching the beam onto a generalized equilibrium envelope, which produces a beam which diminishes in transverse size monotonically with acceleration. This condition minimizes the emittance, which is 1 mm-rad at Q=1 nC. This design is also scaled to produce nearly identical performance at X-band, giving an injector appropriate to running an FEL at the SLAC NLCTA. These designs are insensitive to RF emittance increase, allowing a wide choice of injection phase, and the option to compress the emitted pulse. (8 References).
keywords:
Download | Details | Edit | Delete
title: An Ultra-High Gradient Cerenkov Wakefield Acceleration Experiment at SLAC FFTB
format: conference proceeding
conference: AAC 2004 11th
year: 2004
7 authors: J.B. Rosenzweig | S. Hoover | M. Hogan | P. Muggli | M.C. Thompson | G. Travish | R. Yoder
abstract: The creation of ultra-high current, ultra-short pulse beams (Q=3 nC, ?z= 20 ?m) at the SLAC FFTB has opened the way for very high gradient plasma wakefield acceleration experiments. We study here the use of these beams in a proposed Cerenkov wakefield experiment, where one may excite electromagnetic wakes in a simple dielectric tube with inner diameter of few 100 microns that exceed the GV/m level. We discuss the scaling of the fields with design geometric design parameters, and choice of dielectric. We also examine measurable aspects of the experiment, such as the total coherent Cerenkov radiation energy one may collect, and the expected aspects of dielectric breakdown at high fields.
keywords:
Download | Details | Edit | Delete
title: Experimental measurement of high-gradient standing wave accelerator transport matrix
format: conference proceeding
conference: PAC 1997
year: 1998
3 authors: Sven Reiche | J.B. Rosenzweig | L. Serafini
abstract: This paper presents an experimental study of the transverse beam dynamics of an electron beam in a high-gradient, standing wave linear accelerator. A 3.6 MeV beam from the UCLA RF Photoinjector (SATURNUS) is injected at various phases and rf field amplitudes into the plane wave transformer (PWT) linac (peak acceleration 40 MeV/m), and its transverse dynamics measured by a corrector magnet sweeping method. This method allows us to reconstruct the transverse matrix elements, which are compared to analytical predictions (J.B. Rosenzweig and L. Serafini, Physical Review E 49, 1599 (1994)). The determinant of the experimentally derived matrix is found to be the ratio of the initial to final momentum, verifying the theory, and providing direct evidence of adiabatic damping of transverse trace space. (9 References).
keywords:
Download | Details | Edit | Delete
title: Optimum operation of split RF photoinjectors
format: conference proceeding
conference: PAC 1997
year: 1998
2 authors: L. Serafini | J.B. Rosenzweig
abstract: We describe how to achieve minimum transverse emittance in RF photoinjectors by applying theoretical predictions from a fully analytical model of beam dynamics in a split injector. This device consists of a short two cell (full+partial) RF gun followed by a drift and a booster RF linac. Matching the beam in the booster to the invariant envelope, an equilibrium mode of laminar beam flow, is shown to be the basis of emittance correction. Analytical predictions are compared to numerical simulations, finding excellent agreement. We also show how a further improvement of the beam quality can be obtained by matching the beam out of the booster into a Brillouin flow with proper control of the envelope oscillations. If these are actually coherent plasma oscillations in the laminar regime, then the normalized RMS transverse emittance can be even further reduced. (7 References).
keywords:
Download | Details | Edit | Delete
title: Space charge dominated envelope dynamics of asymmetric beams in RF photoinjectors
format: conference proceeding
conference: PAC 1997
year: 1998
3 authors: J.B. Rosenzweig | S. Anderson | L. Serafini
abstract: While it has been proposed for several years that strongly asymmetric (sigma_x >> sigma_y) beams can be employed in RF photoinjectors to obtain asymmetric emittances for linear collider applications, it is known that the emittances obtained directly from RF photocathode guns are not suitably small for this purpose. Because of this, simulation work has been performed in an attempt to apply the principle of emittance compensation to recover the small and asymmetric emittances after suitable focusing and acceleration of photoinjector beams. In order to guide this difficult three-dimensional analysis, we present an extension of a previous theoretical model of the emittance compensation process in axisymmetric photoinjectors. In the extended model, we first analyze the general quadrupolar oscillations in a symmetric accelerating system, and then proceed to examine a propagation mode under asymmetric focusing. This mode is a generalization of the previously analyzed axisymmetric invariant envelope, allowing an optimization of the compensation process. Design philosophies, including rf cavity considerations, are included in the discussion.
keywords:
Download | Details | Edit | Delete
title: Measurement of the variation of machine parameters and the effect of the power supplies ripple on the instantaneous tunes at SPEAR
format: conference proceeding
conference: PAC 1997
year: 1998
5 authors: A. Terebilo | C. Pellegrini | M. Cornacchia | Corbett, J. | Martin, D.
abstract: For long term stability analysis, time variation of tunes is important. We have proposed and tested a technique for measuring the magnitude of this variation. This was made possible by using tune extraction algorithms that require small number of turns thus giving an instantaneous tune of the machine. In this paper we demonstrate the measured effect of the tune modulation with 60 Hz power supplies ripple, power line interference from the SLAC linac operating at 30 Hz repetition rate, and non-periodic variation. (8 References).
keywords:
Download | Details | Edit | Delete
title: An Optimal Design for a THz Dielectric-Loaded Slab-Symmetric Accelerator
format: conference proceeding
conference: AAC 2004 11th
year: 2004
2 authors: R.B. Yoder | J.B. Rosenzweig
abstract: A slab-symmetric dielectric-loaded accelerator structure, consisting of a vacuum gap between dielectric-lined conducting walls, is analyzed theoretically and computationally. The device is to be resonantly excited by an external laser source of wavelength 340
keywords:
Download | Details | Edit | Delete
title: Beam-plasma interaction experiments at the UCLA Neptune Laboratory
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: M.C. Thompson | C. E. Clayton | R. J. England | J.B. Rosenzweig | Suk, H.
abstract: We are currently planning several beam-plasma interaction experiments using the high quality 16 MeV electron beam produced by the Neptune 1.625-cell photoinjector and PWT linac. The underdense (n_b > n_0) plasma lens experiment will examine the focusing of a 4 nC beam of 30 psec pulse duration as it passes through a thin 2 cm Ar plasma lens. We are also developing a negative R_56 compressor beamline that will allow us to create ramped sub-picosecond beams of a shape well suited for driving large amplitude plasma wake fields and producing high transformer ratios. Simulations made using the 2-1/2 dimensional particle-in-cell code MAGIC indicate that we could use these ramped beams to produce fields of up to 10 GeV/m in a 10(16) cm(-3) plasma. Ramped beams are also suitable for driving plasma density gradient trapping experiments. When such a beam passes through a region where the plasma density drops suddenly the fast variation of the wake fields traps several pC of plasma electrons in the accelerating portion of the wake field.
keywords:
Download | Details | Edit | Delete
title: Experimental nonlinear beam dynamics studies at SPEAR
format: conference proceeding
conference: PAC 1997
year: 1998
5 authors: A. Terebilo | C. Pellegrini | M. Cornacchia | Corbett, J. | Martin, D.
abstract: The frequency map analysis of a Hamiltonian system recently introduced to accelerators physics in combination with turn-by-turn phase space measurements opens new experimental opportunities for studying nonlinear dynamic in storage rings. In this paper we report on the experimental program at SPEAR having the goal of measuring the frequency map of the machine. In this paper we discuss the accuracy of the instantaneous tune extraction from experimental data and demonstrate the possibility of frequency map measurement. (7 References).
keywords:
Download | Details | Edit | Delete
title: An Inverse Compton Scattering Radiation Source via Self-Guiding in a Plasma
format: conference proceeding
conference: AAC 2006 12th
year: 2006
2 authors: R. B. Yoder | J.B. Rosenzweig
abstract: In an inverse-Compton scattering source, in which a relativistic electron beam collides with a high-power laser pulse, the x-ray flux produced is proportional to the brightness of the two beams and the size of their overlap region in three-dimensional space. In vacuum, this overlap is limited by the diffraction of the two beams, but the diffraction limit can be overcome by confining both beams in a plasma guiding channel. A dense, bunched electron beam injected into an underdense plasma will self-guide via ``blowout,'' in which the beam head creates a focusing ion channel through which the body of the beam is guided; this same channel can also guides a counterpropagating laser beam. Constraints include the need for long laser wavelength (1 to 10 ?m) and high beam densities. We present a possible configuration for a gamma-ray source using 180� Compton scattering in a uniform plasma, including 2D simulation results. Estimated photon yields are up to a factor of 5 larger than in vacuum scattering, with production of nearly 1010 photons per nanocoulomb of electron beam charge.
keywords:
Download | Details | Edit | Delete
title: Saturation measurements of a visible SASE FEL
format: conference proceeding
conference: PAC 2001
year: 2001
14 authors: A. Tremaine | P. Frigola | A. Murokh | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | M. Babzien | I. Ben-Zvi | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X. J. Wang | V. Yakimenko
abstract: VISA (visible to infrared SASE amplifier) is an FEL designed to obtain high gain at a radiation wavelength of 800 nm. Large gain is achieved by driving the FEL with the 71 MeV, high brightness beam of the Accelerator Test Facility (ATF) and using a novel, strong focusing, 4 m long undulator with a gap of 6 mm and a period of 1.8 cm. We report measurements of exponential gain, saturation, and spectra of the FEL radiation intensity. (11 References).
keywords:
Download | Details | Edit | Delete
title: Beam Dynamics in a Hybrid Standing Wave-Traveling Wave Photoinjector
format: conference proceeding
conference: AAC 2006 12th
year: 2006
11 authors: J.B. Rosenzweig | D. Alesini | A. Boni | M. Ferrario | L. Ficcadenti | A. Fukusawa | A. Mostacci | B. O'Shea | L. Palumbo | B. Spataro | V. Fusco
abstract: We discuss the dynamics of of a photoinjector beam in a hybrid traveling wave-standing wave photoinjector. With the field profile deduced from electromagnetic simulations, it is seen that the acceleration program induces strong velocity bunching. The beam dynamics in this scenario are explored using UCLA PARMELA. With a solenoid field overlaid on the TW section one may control emittance oscillations during bunching and acceleration. It is seen that the S-band device currently under development at UCLA may produce a 1 nC, 21 MeV, 100 micron rms pulse length beam, with emittance of 3 mm-mrad. Applications of this beam for creating coherent radiation are discussed.
keywords:
Download | Details | Edit | Delete
title: Dynamics of a Driver Beam Propagating in an Underdense Plasma with a Downward Density Transition
format: conference proceeding
conference: PAC 2001
year: 2001
7 authors: Suk, H. | N. Barov | R. J. England | E. Esarey | G. Kim | J.B. Rosenzweig | M.C. Thompson
abstract: When a short electron beam propagates in an underdense plasma (plasma density n_p < beam density n_b) with a downward density transition, it is known that some background plasma electrons are trapped and accelerated by the plasma wakefield[1]. Beam quality of the trapped plasma electrons is severely affected by the wakefield that is generated by the driving electron beam, so dynamics and instabilities of the driver beam are very important. In this paper, we present some simulation results on the self-trapping and driver beam dynamics.
keywords:
Download | Details | Edit | Delete
title: A plane-wave-transformer photoelectron linac
format: conference proceeding
conference: PAC 1997
year: 1998
7 authors: D. Yu | Lee, T. | Rajagopalan, S. | Chen, J. | C. Pellegrini | J.B. Rosenzweig | X. Ding
abstract: We develop a novel photoelectron linear accelerator using a plane wave transformer (PWT) design. In this design, the input RF power is coupled to the accelerating cavities via a large concentric manifold cavity. The scheme makes possible very strong coupling between the accelerating cells, and relaxes manufacturing tolerances. The compact photoelectron linac integrates a photocathode directly into a PWT linac structure, and eliminates the drift space between a photoinjector and the linac which would otherwise lengthen the electron bunches. Using an emittance compensation scheme, the PWT photoelectron linac produces a high-brightness beam. We have demonstrated by simulations the feasibility of a 20 MeV PWT photoelectron linac design with a set of eleven iris-loaded disks suspended and cooled by four water tubes inside a large cylindrical tank. (5 References).
keywords:
Download | Details | Edit | Delete
title: Limits on production of narrow band photons from inverse Compton scattering
format: conference proceeding
conference: AAC 2006 12th
year: 2006
2 authors: J.B. Rosenzweig | O.B. Williams
abstract: In using the inverse Compton scattering (ICS) interaction as a high brilliance, short wavelength radiation source, one collides two beams, one an intense laser, and the other a high charge, short pulse electron beam. In order to maximize the flux of photons from ICS, one must focus both beams strongly, which implies both use of short beams and the existence of large angles in the interaction. One aspect of brilliance is the narrowness of the wavelength band emitted by the source. This paper explores the limits of ICS-based source brilliance based on inherent wavelength broadening effects that arise due to focal angles, laser energy density, and finite laser pulse length effects. It is shown that for a nominal 1% desired bandwidth, that one obtains approximately one scattered photon per electron in a head-on collision geometry
keywords:
Download | Details | Edit | Delete
title: Charge and Wavelength Scaling of RF Photoinjector Designs
format: conference proceeding
conference: PAC 1995
year: September 21, 1994
2 authors: J.B. Rosenzweig | E. Colby
abstract: The optimum design of an emittance compensated rf photoinector is very complicated and time-consuming, relying heavily on multi-particle simulations without good analytical models as a guide. Emittance compensated designs which have been developed, however, can be used to generate other designs with no additional effort if the original design is scaled correctly. This paper examines the scaling of rf photoinjector design with reqpect to charge and wavelength, and presents emittance and brightness scaling laws for these variables. Parametric simulation studies are presented to illustrate these scaling laws. Deviations from scaling and practical considerations are also discussed.
keywords:
Download | Details | Edit | Delete
title: The SPARC Project: A High Brightness Electron Beam Source at LNF to Drive a SASE-FEL Experiment
format: conference proceeding
conference: PAC 2003
year: 2003
75 authors: D. Alesini | S. Bertolucci | M. Biagini | C. Biscari | R. Boni | M. Boscolo | M. Castellano | A. Clozza | G. Di Pirro | A. Drago | A. Esposito | M. Ferrario | V. Fusco | A. Gallo | A. Ghigo | S. Guiducci | M. Incurvati | C. Ligi | F. Marcellini | M. Migliorati | C. Milardi | L. Palumbo | L. Pellegrino | M. Preger | P. Raimondi | R. Ricci | C. Sanelli | M. Serio | F. Sgamma | B. Spataro | A. Stecchi | A. Stella | F. Tazzioli | C. Vaccarezza | M. Vescovi | C. Vicario | M. Zobov | F. Alessandria | A. Bacci | I. Boscolo | F. Broggi | S. Cialdi | C. DeMartinis | D. Giove | C. Maroli | V. Petrillo | M. Rome | L. Serafini | D. Levi | M. Mattioli | L. Catani | E. Chiadroni | S. Tazzari | R. Bartolini | F. Ciocci | G. Dattoli | A. Doria | F. Flora | G. P. Gallerano | L. Giannessi | E. Giovenale | G. Messina | L. Mezi | P. L. Ottaviani | L. Picardi | M. Quattromini | A. Renieri | C. Ronsivalle | A. Cianchi | A. D'Angelo | R. Di Salvo | A. Fantini | D. Moricciani | C. Schaerf | J.B. Rosenzweig
abstract: The Project SPARC (Sorgente Pulsata e Amplificata di Radiazione Coerente), proposed by a collaboration among ENEA-INFN-CNR-Universita' di Roma "Tor Vergata" -INFM-ST, was recently approved by the Italian Government and will be built at LNF of INFN. The aim of the project is to promote an R&D activity oriented to the development of a coherent ultra-brilliant X-ray source in Italy. This collaboration has identified a program founded on two main issues: the generation of ultra-high peak brightness electron beams and of resonant higher harmonics in the SASE-FEL process.
keywords:
Download | Details | Edit | Delete
title: Is the X-ray FEL the 4th generation light source?
format: conference proceeding
conference: EPAC 1998
year: 1998
1 author: C. Pellegrini
abstract: Recent theoretical and experimental work has led to important advances in the physics of Self-Amplified Spontaneous Emission free-electron-lasers (SASE-FELs), and in the production of high brightness, high energy electron beams. This work has made possible the design and construction of X-ray FELs at a few to 0.1 nm. The X-ray FEL has the characteristics required for a ''4th Generation Light Source'': diffraction limited radiation, subpicosecond pulse length, peak and average brightness largely exceeding that of 3rd generation sources. We review the status of SASE-FELs, and of the X-ray FEL projects.
keywords:
Download | Details | Edit | Delete
title: Beam compression experiments using the UCLA/ATF compressor
format: conference proceeding
conference: AAC 2006 12th
year: 2006
13 authors: D. Schiller | E. Hemsing | J.B. Rosenzweig | M.P. Dunning | G. Andonian | A. Murokh | A.M. Cook | Sven Reiche | M. Babzien | K. Kusche | V. Yakimenko | L. Palumbo | C. Vicario
abstract: We review recent experimental results from the BNL ATF using the compressor built by UCLA. The measurements discussed include: first observation of short wavelength coherent edge radiation angular/wavelength spectrum and spectrum, sub-100 fsec pulse-length coherent transition autocorrelation measurements, and longitudinal and transverse phase space distortions. Extension of these measurements, as well as those which can be made possible by a new X-band traveling wave deflector being developed in an industrial collaboration, are examined.
keywords: quindi  
Download | Details | Edit | Delete
title: Design and Operation of Pegasus Thermionic Cathode
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: P. Frigola | G. Andonian | Sven Reiche | J.B. Rosenzweig | S. Telfer | G. Travish
abstract: A new thermionic cathode has been developed and installed for use on The PEGASUS plane wave transformer injector. The novel design of the LaB6 cathode allows for thermionic emission as well as photoinjector operation. Test stand measurements as well as in situ operational experience are reported.
keywords:
Download | Details | Edit | Delete
title: Laminar flow in non-relativistic intense proton beams
format: conference proceeding
conference: EPAC 1998
year: 1998
2 authors: L. Serafini | J.B. Rosenzweig
abstract: An approach to the envelope description of laminar non-relativistic particle beams is presented, which describes a new kind of equilibrium flow for strongly space charge dominated proton beams subject to acceleration in RF Linacs. The analysis is based on the extension of the invariant envelope concept, recently introduced in the field of RF photo-injectors[1], to nonrelativistic particle beams whose envelope is dominated by coherent plasma oscillations instead of incoherent betatron motion associated to thermal rms emittance. An exact analytical solution of the rms envelope equation is presented, describing both the laminar regime and the transition to the thermal regime: the impact of this new beam equilibrium on the design of high intensity Linacs is discussed.
keywords:
Download | Details | Edit | Delete
title: A Slab-Symmetric Dielectric-Loaded Structure for High-Gradient Acceleration at THz
format: conference proceeding
conference: PAC 2003
year: 2003
2 authors: R. B. Yoder | J.B. Rosenzweig
abstract: We present a design for a slab-symmetric accelerating structure to be resonantly excited at terahertz frequencies. The device, consisting of a vacuum gap between dielectric-lined walls, combines the advantages of a slab geometry (including strong suppression of transverse beam wakefields and low power density) with the existence of a resonant mode having phase synchronism with relativistic electrons. Accelerating fields of hundreds of MeV/m are predicted when the structure is powered by a high-power FIR radiation source in development at UCLA. Simulation of the structure fields is described and compared with theory, and an experimental program is discussed.
keywords:
Download | Details | Edit | Delete
title: A High Voltage Extractor with Photocathodes
format: conference proceeding
conference: EPAC 1998
year: 1999
7 authors: G. Travish | D. Giove | P. Michelato | C. Pagani | P. Pierini | L. Serafini | D. Sertore
abstract: We describe a system designed for photocathode testing and beam dynamics studies which is based on a high voltage extractor and a sub–ps drive laser. The system’s distinctive characteristics are the ability to run in the short bunch regime — where the dynamics are not governed by the Child–Langmuir law — and the anticipated availability of both transverse and longitudinal beam diagnostics to determine the full beam distribution. The system consists of a pseudo parallel plate 100 kV DC gun with a removable cathode and a cathode–anode gap of 8 mm, yielding a cathode field of up to 10 MV/m. The drive laser is a Nd:Glass system capable of producing over 200 ?J at 264 nm with a pulse length adjustable from approximately 250 fs to over 1 ps. The goals of the system, described in this paper, are to support ongoing photocathode studies, including measuring high current density extraction from prepared cathodes and investigating the effect of surface variation of the quantum efficiency. Additional studies foreseen include parameterizing the effect of surface variations on the transverse emittance, and exploring beam dynamics such as the short bunch blow out regime which has recently been proposed as a way to produce uniform ellipsoidal charge density distributions[1].
keywords:
Download | Details | Edit | Delete
title: A Helical Undulator Wave-guide Inverse Free-Electron Laser
format: conference proceeding
conference: AAC 2004 11th
year: 2004
8 authors: J.B. Rosenzweig | N. Bodzin | P. Frigola | C. Joshi | P. Musumeci | C. Pellegrini | S. Tochitsky | G. Travish
abstract: With recent success in high gradient, high-energy gain IFEL experiments at the UCLA Neptune Laboratory, future experiments are now being contemplated. The Neptune IFEL was designed to use a tightly focused, highly diffracting, near-TW peak power 10 micron laser. This choice of laser focusing, driven by power-handling limitations of the optics near the interaction region, led to design and use of a very complex undulator, and to sensitivity to both laser misalignment and focusing errors. As these effects limited the performance of the IFEL experiment, a next generation experiment at Neptune has been studied which avoids the use of a highly diffractive laser beam through use of a waveguide. We discuss here the choice of low-loss waveguide, guided mode characteristics and likely power limitations. We also examine a preferred undulator design, which is chosen to be helical in order to maximize the acceleration achieved for a given power. With the limitations of these laser and undulator choices in mind, we show the expected performance of the IFEL using 1D simulations. Three-dimensional effects are examined, in the context of use of a solenoid for focusing and acceleration enhancement.
keywords:
Download | Details | Edit | Delete
title: Pulse Compression via Velocity Bunching with the LLNL Thomson X-Ray Source Photoinjector
format: conference proceeding
conference: PAC 2003
year: 2003
5 authors: S. Anderson | W. J. Brown | A.M. Tremaine | P. Musumeci | J.B. Rosenzweig
abstract: We report the compression of a high brightness, relativistic electron beam to rms lengths below 300 femtoseconds using the velocity compression technique in the LLNL Thomson X-ray source photoinjector. The results are consistent with analytical and computational models of this process. The emittance evolution of the beam during compression is investigated in simulation and found to be controllable with solenoid focusing.
keywords:
Download | Details | Edit | Delete
title: Beam transport, acceleration and compression studies in the Fermilab high-brightness photoinjector
format: conference proceeding
conference: Linear Accelerator Conference 1998
year: 1998
20 authors: J.P. Carneiro | R. Carrigan | Champion, M. S. | A. Cianchi | E.R. Colby | P. L. Colestock | H. T. Edwards | Fuerst, J. D. | W. Hartung | Koepke, K. P. | Kuchnir, M. | Spentzouris, L. K. | Fitch, M. J. | Fry, A. R. | Melissinos, A. C. | Taylor, B. D. | P. Michelato | Sertore, D. | C. Pagani | J.B. Rosenzweig
abstract: A photoinjector is being constructed in order to produce a pulse train of up to 800 electron bunches, each with 8 nC of charge and a 3.5 ps rms bunch length. The spacing between bunches within a train is 1 s and the train repetition rate is 1?10 Hz. The desired transverse emittance is <20 mm mrad. An rf photo-gun delivers a bunched 4?5 MeV beam which will be accelerated to 14?18 MeV by a 9- cell superconducting cavity and compressed magnetically. Measurements have been done on the beam delivered by a first prototype rf gun; installation of a new rf gun, the 9-cell cavity, and the bunch compressor is in progress.
keywords:
Download | Details | Edit | Delete
title: Design and Status of the VISA II Experiment
format: conference proceeding
conference: PAC 2003
year: 2003
12 authors: G.Andonian | R.Agustsson | A. Murokh | C.Pellegrini | Sven Reiche | J.B. Rosenzweig | G. Travish | M. BABZIEN | I. Ben-Zvi | V. Yakimenko | L. Palumbo | C. VICARIO
abstract: VISA II is the follow-up project to the successful Visible to Infrared SASE Amplifier (VISA) experiment at the Accelerator Test Facility (ATF) in Brookhaven National Lab (BNL). This paper will report the motivation for and status of the two main experiments associated with the VISA II program. One goal of VISA II is to perform an experimental study of the physics of a chirped beam SASE FEL at the upgraded facilities of the ATF. This requires a linearization of the transport line to preserve energy chirping of the electron beam at injection. The other planned project is a strong bunch compression experiment, where the electron bunch is compressed in the chicane, and the dispersive beamline transport, allowing studies of deep saturation.
keywords:
Download | Details | Edit | Delete
title: Operation of the APS RF Gun
format: conference proceeding
conference: Linear Accelerator Conference 1998
year: 1998
8 authors: J. W. Lewellen | S. Biedron | A. Lumpkin | S. V. Milton | A. Nassiri | S. Pasky | G. Travish | M. White
abstract: The Advanced Photon Source (APS) has a thermioniccathode rf gun system capable of providing beam to the APS linac. The gun system consists of a 1.6-cell thermionic-cathode rf gun, a fast kicker for beam current control, and an alpha magnet for bunch compression and injection into the APS linac line. This system is intended for use both as an injector for positron creation, and as a first beam source for the Low-Energy Undulator Test Line (LEUTL) project [1]. The first measured performance characteristics of the gun are presented.
keywords:
Download | Details | Edit | Delete
title: An Ultra-High Gradient Cerenkov Wakefield Acceleration Experiment at SLAC FFTB
format: conference proceeding
conference: AAC 2004 11th
year: 2004
7 authors: J.B. Rosenzweig | S. Hoover | M. Hogan | P. Muggli | M.C. Thompson | G. Travish | R. B. Yoder
abstract: The creation of ultra-high current, ultra-short pulse beams (Q=3 nC, ) at the SLAC FFTB has opened the way for very high gradient plasma wakefield acceleration experiments. We study here the use of these beams in a proposed Cerenkov wakefield experiment, where one may excite electromagnetic wakes in a simple dielectric tube with inner diameter of few100 microns that exceed the GV/m level. We discuss the scaling of the fields with design geometric design parameters, and choice of dielectric. We also examine measurable aspects of the experiment, such as the total coherent Cerenkov radiation energy one may collect, and the expected aspects of dielectric breakdown at high fields.
keywords:
Download | Details | Edit | Delete
title: Status of the UCLA PEGASUS Laboratory
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: G. Andonian | P. Frigola | Sven Reiche | J.B. Rosenzweig | S. Telfer | G. Travish
abstract: The PEGASUS laboratory is a versatile radiation facility dedicated to the advancement of novel concepts in beam physics. The installation of a new LaB$_6$ cathode will allow for both thermionic emission and photoinjection operation. The PEGASUS plane wave transformer injector has been conditioned to 20 MW of RF power. Recent operations show a 15 MeV dark current beam that will be used for beam radiation studies. An upgrade to the drive laser system has been explored and will be realized shortly. This paper will describe and report the status of the various subsystems of the PEGASUS laboratory and outline the experiments underway, such as innovative beam instrumentation, surface effects in optical transition radiation, Thomson scattering, and waveguide SASE FEL.
keywords:
Download | Details | Edit | Delete
title: Start to End Simulations for the SPARX Proposal
format: conference proceeding
conference: PAC 2003
year: 2003
18 authors: M. Biagini | M. Boscolo | M. Ferrario | V. Fusco | S. Guiducci | B. Spataro | C. Vaccarezza | M. Zobov | L. Serafini | R. Bartolini | G. Dattoli | L. Giannessi | L. Mezi | M. Quattromini | C. Ronsivalle | E. Chiadroni | P. Emma | J.B. Rosenzweig
abstract: The resource allocation in the Italian National Research Plan (PNR) for the development of a coherent ultra-brilliant X-ray source, based on a SASE Free Electron Laser, brought about the formation of a CNR-ENEA-INFN- University of Roma "Tor Vergata" study group. A conceptual design study has been developed and possible schemes for linac sources have been investigated leading to the SPARX proposal. We report in this paper the results of start to end simulations concerning the option based on an S-band normal conducting linac. Saturation at 1-10 nm can be achieved in a 40 m long undulator provided the peak current delivered by the linac is 2.5 kA at 2.5 GeV with rms normalized slice emittance of the order of 1 _m and the energy spread less than 0.1%. One of the most critical systems is the bunch compressor. The effects on beam dynamics of a magnetic chicane system and a rectilinear RF compressor (based on velocity bunching), integrated in a high brightness photoinjector, are analyzed and compared in this paper.
keywords:
Download | Details | Edit | Delete
title: Theoretical evaluation of the LCLS X-Ray Free-Electron Laser performance
format: conference proceeding
conference: FEL 2003 25th
year: 2003
4 authors: Sven Reiche | C. Pellegrini | P. Emma | Nuhn, H. D.
abstract: In this paper we evaluate the performance of the LCLS FEL, including all known physical effects from the electron source to the undulator exit which determine the X-ray pulse characteristics. The wavelength range considered is from the 15 to 1.5 Angstrom, with an extension to 0.5 Angstrom using the third harmonic. The results of this work have been useful to identify areas in the LCLS design where improvements could be made, thus optimizing the system performance.
keywords:
Download | Details | Edit | Delete
title: The SLAC soft X-ray high power FEL
format: conference proceeding
conference: FEL 1993 15th
year: 1994
23 authors: C. Pellegrini | J.B. Rosenzweig | G. Travish | K. Bane | R. Boyce | G. Loew | P. Morton | H. D. Nuhn | J. Paterson | P. Pianetta | T. Raubenheimer | J. Seeman | R. Tatchyn | V. Vylet | H. Winick | K. Halbach | K. J. Kim | M. Xie | D. Prosnitz | E. T. Scharlemann | R. Bonifacio | L. De Salvo | P. Pierini
abstract: We discuss the design and performance of a 2 to 4 nm FEL operating in self-amplified spontaneous emission (SASE), using a photoinjector to produce the electron beam, and the SLAC linac to accelerate it to an energy of about 7 GeV. Longitudinal bunch compression is used to increase the peak current to 2.5 kA, while reducing the bunch length to about 40 mu m. The FEL field gain length is about 6 m, and the saturation length is about 60 m. The saturated output power is about 10 GW, corresponding to about 10/sup 14/ photons in a single pulse in a bandwidth of about 0.1%, with a pulse duration of 0.16 ps. Length compression, emittance control, phase stability, FEL design criteria, and parameter tolerances are discussed. (15 References).
keywords:
Download | Details | Edit | Delete
title: Prospects for high power linac coherent light source (LCLS) development in the 1000 angstrom-1 angstrom wavelength range
format: conference proceeding
conference: International Colloquium on X-Ray Lasers 4th
year: 1994
26 authors: R. Tatchyn | K. Bane | R. Boyce | G. Loew | R. Miller | H. D. Nuhn | D. Palmer | J. Paterson | T. Raubenheimer | J. Seeman | H. Winick | D. Yeremian | C. Pellegrini | J.B. Rosenzweig | G. Travish | D. Prosnitz | E. T. Scharlemann | S. Caspi | W. Fawley | K. Halbach | K. J. Kim | R. Schlueter | M. Xie | R. Bonifacio | L. De Salvo | P. Pierini
abstract: Electron bunch requirements for single-pass saturation of a free-electron laser (FEL) operating at full transverse coherence in the self-amplified spontaneous emission (SASE) mode include: 1) a high peak current, 2) a sufficiently low relative energy spread, and 3) a transverse emittance epsilon (r-m) satisfying the condition epsilon <= lambda /4 pi , where lambda (m) is the output wavelength of the FEL. In the insertion device that induces the coherent amplification, the prepared electron bunch must be kept on a trajectory sufficiently collinear with the amplified photons without significant dilution of its transverse density. In this paper we discuss a Linac coherent light source (LCLS) based on a high energy accelerator such as, e.g., the 3 km S-band structure at the Stanford Linear Accelerator Center (SLAC), followed by a long high-precision undulator with superimposed quadrupole (FODO) focusing, to fulfill the given requirements for SASE operation in the 1000 angstrom-1 angstrom range. The electron source for the linac, an RF gun with a laser-excited photocathode featuring a normalized emittance in the 1-3 mm-mrad range, a longitudinal bunch duration of the order of 3 ps, and approximately 10(-9) C/bunch, is a primary determinant of the required low transverse and longitudinal emittances. Acceleration of the injected bunch to energies in the 5-25 GeV range is used to reduce the relative longitudinal energy spread in the bunch, as well as to reduce the transverse emittance to values consistent with the cited wavelength regime. Two longitudinal compression stages are employed to increase the peak bunch current to the 2-5 kA levels required for sufficiently rapid saturation. The output radiation is delivered, via a grazing-incidence mirror bank, to optical instrumentation and a multi-user beam line system. Technological requirements for LCLS operation at 40 angstroms, 4.5 angstroms, and 1.5 angstroms are examined.
keywords:
Download | Details | Edit | Delete
title: Start-to-End Simulations for the LCLS X-Ray Free-Electron Laser
format: conference proceeding
conference: FEL 2003 25th
year: 2003
7 authors: Sven Reiche | C. Pellegrini | P. Emma | Nuhn, H. D. | Limborg, C. G. | Borland, M. | W. Fawley
abstract: The LCLS Free-Electron Lasers operates in the wavelength range of 1.5-15 Angstrom, using an electron beam with an energy between 4.5 and 14.5 GeV. The generation of the electron beam, the preservation of its brightness during acceleration and compression, and the amplififcation of the spontaneous radiation within the FEL can only be described by a consistent set of simulation codes. We preset the change in the FEL performance with respect to the LCLS design case, when various effects are included, altering the electron beam distribution and motion (e.g. wake fields, CSR, magnet misalignment or field errors of the undulator field). To distinguish the individual contribution of each effect, multiple start-end simulations are performed, including step by step additional effects and, thus, approaching a more and more realistic model of the LCLS FEL.
keywords:
Download | Details | Edit | Delete
title: Initial measurements of the UCLA RF photoinjector
format: conference proceeding
conference: FEL 1993 15th
year: 1994
2 authors: S. Hartman | M. Hogan
abstract: An RF photocathode gun which, along with a compact linac, forms the injection system for a planned 10 mm free-electron laser amplifier experiment, has been commissioned in the Particle Beam Physics Laboratory at UCLA. This high-gradient gun, based on the Brookhaven design, has emitted several picosecond, [right angle bracket]100 A electron beams of up to 4 MeV in energy. These beams have been characterized by a variety of diagnostics. The quantum efficiency of the copper cathode used has been measured at normal incidence, and at 70 degrees incidence, where the polarization dependence was also examined. Limits on laser intensity due to surface damage, and to longitudinal space charge suppression of photoemission have been explored. The energy and energy spread of the beam were characterized using a dipole spectrometer, while the time structure was examined using a picosecond resolution streak camera. Both energy spread and pulse length were found to be adversely affected by longitundinal space charge forces. The emittance of the beam was measured using the pepper pot Technique, and its dependence on space charge and rf phase were found. The impact of these results on imporving the design and operation of high brightness photoinjectors is discussed, in particular with respect to SASE FEL amplifiers such as the UCLA 10mm FEL, and the proposed SLAC X-ray FEL.
keywords:
Download | Details | Edit | Delete
title: Experimental non linear beam dynamics studies with a turn-by-turn phase space monitor at SPEAR
format: conference proceeding
conference: ICFA Workshop on Nonlinear and Collective Phenomena in Beam Physics
year: 1999
3 authors: A. Terebilo | C. Pellegrini | M. Cornacchia
abstract: About 10 years ago the possibility of using turn-by-turn phase beam position monitors to gain insight into phase space dynamics of a single particle in a storage ring raised some interest among accelerator physicists. It was soon argued that Landau damping and collective effects would seriously complicate the interpretation of data. We have established that in SPEAR it is possible to lock a single bunch into a collective 'rigid body' mode. When in this mode the bunch will behave similar to a super particle of finite size with the charge equal to that of the bunch. In this paper we report on experiments that demonstrate this effect. We also numerically study the strong coupling limit, in which the transition to 'rigid body' motion occurs, for the two models proposed earlier. We present the experiments on non-linear resonance crossing and frequency map measurement in the 'super particle' framework. (11 References).
keywords:
Download | Details | Edit | Delete
title: Free-Electron Lasers as Pumps for High-Energy Solid-State Lasers
format: conference proceeding
conference: FEL 2003 25th
year: 2004
3 authors: G. Travish | J. Crane | A. Tremaine
abstract: High average-power free-electron lasers may be useful for pumping high peak-power solid-state laser-amplifiers. At very high peak-powers, the pump source for solid-state lasers is non-trivial: flash lamps produce thermal problems and are unsuitable for materials with short florescence-times, while diodes can be expensive and are only available at select wavelengths. FELs can provide pulse trains of light tuned to a laser material's absorption peak, and florescence lifetime. An FEL pump can thus minimize thermal effects anad potentially allow for new laser materials to be used. This paper examines the design of a high average-power, effecient high-gain FEL for use as a pump source. Specifically, the cases of a 100 J class pump, and a 100 TW-class laser at a planned fourth-generation light-source are considered.
keywords:
Download | Details | Edit | Delete
title: A millimeter wave FEL driven by a photocathode RF linac
format: conference proceeding
conference: FEL 1993 15th
year: 1994
11 authors: R. Zhang | C. Pellegrini | J.B. Rosenzweig | G. LeSage | F. Hartemann | D. McDermott | C. Joshi | N. Luhmann | P. Pierini | de Salvo, L. | Bonifacio, R.
abstract: We present the design of a millimeter wave FEL based on the UCLA photocathode RF linac. The linac energy can be varied between 5 and 18 MeV. The electron pulse duration is 2 ps FWHM, with a peak current exceeding 150 A. The FEL is designed to operate in the high-gain Compton regime, controlling the slippage with the propagating radiation in a waveguide. The design permits the exploration of the basic FEL physics in this regime, including the exploration of saturation and lethargy in the superradiant and steady state regime. (15 References).
keywords:
Download | Details | Edit | Delete
title: A new method for pumping an optical klystron
format: conference proceeding
conference: International Workshop on Coherent and Collective Properties in the Interaction of Relativistic Electrons and Electromagnetic Radiation
year: 1985
8 authors: G. Vignola | R. R. Freeman | B.M. Kincaid | C. Pellegrini | A. Luccio | J. Murphy | J. Galayda | A. van Steenbergen
abstract: A novel method of operation for a transverse optical klystron (TOK) is proposed. The TOK is a device in which a relativistic electron beam produces tunable coherent radiation at short wavelengths by interacting with a powerful external laser and an undulator field. The authors show that, by selecting the external laser wavelength to be one of the harmonics in the undulator radiation spectrum, excellent output at short wavelengths can be realized with significantly reduced performance requirements for the undulator magnet and the storage ring providing the electron beam. (10 References).
keywords:
Download | Details | Edit | Delete
title: RESULTS FROM THE UCLA/FNPL UNDERDENSE PLASMA LENS EXPERIMENT
format: conference proceeding
conference: Erice 2005
year: 2006
11 authors: M.C. Thompson | H. Badakov | J.B. Rosenzweig | G. Travish | H. Edwards | R. Fliller | G. M. Kazakevich | P. Piot | J. Santucci | J. Li | R. Tikhoplav
abstract: A gaussian underdense plasma lens with peak density 5 x 1012 cm?3 and a full width half maximum (FWHM) length of 2.2 cm has been used to focus a relativistic electron beam. This plasma lens is equivalent in strength to a quadrupole magnet with a 150 T/m field gradient. The lens focused a 15 MeV, 16 nC electron beam with initial dimensions ?x,y ? 650 ?m and ?z ? 6.5 mm onto an optical transition radiation (OTR) screen ?2 cm downstream of the lens. The average transverse area of the plasma focused electron beam was typically demagnified by a factor of 23. The evolution of the beam envelope in the area near the beam waist was measured for both round beams and asymmetric beams with x:y aspect ratios as large as 1:5. The light from the OTR screen in the round beam case was also imaged into a streak camera in order to directly measure the correlation between z and ? within the beam.
keywords:
Download | Details | Edit | Delete
title: Longitudinal Beam-Beam Effects in Circular Colliders
format: conference proceeding
conference: PAC 1993
year: 1993
2 authors: M. Hogan | J.B. Rosenzweig
abstract: The longitudinal beam-beam interaction, which can lead to incoherent heating, synchrobctatron coupling, and coherent longitudinal instabilities in circular colliders, is examined. This analysis discusses two types of energy kicks, those due to the transverse particle motion coupling to the electric portion of the transverse kick, and those derived from the inductive electric field induced near the interaction, which is obtained from the transverse kick through use of a generalization of the Panofsky-Wenzel Theorem. Implications for low energy e+e- colliders (phi & B factories) with beams crossing head-on, and at finite angles, with and without crab crossing, are discussed.
keywords:
Download | Details | Edit | Delete
title: Limitations on the resolution of YAG:Ce beam profile monitor for high brightness electron beam
format: conference proceeding
conference: ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams 2nd
year: 2000
5 authors: A. Murokh | V. Yakimenko | E. Johnson | X.J. Wang | J.B. Rosenzweig
abstract: The performance of single crystal YAG:Ce (Y_(3)Al_(5)O_(12)) beam profile monitors was studied for transverse masurements on the high brightness ultrarelativistic electron beam at Accelerator Test Facility (ATF) at BNL. The test demonstrated systematic intensity dependent beam enlargement on YAG monitors, compared to other diagnostics. Possible mechanisms of the effect have been studied. The quantitative examination was performed and compared to the developed phenomenological models. Limitations on the use of YAG:Ce diagnostics are discussed with respect to the high-brightness electron sources.
keywords:
Download | Details | Edit | Delete
title: Performance simulation and parameter optimization for high gain short wavelength FEL amplifiers
format: conference proceeding
conference: FEL 1994 16th
year: 1995
1 author: G. Travish
abstract: The designers of short wavelength FELs must rely on theoretical and numerical predictions since no experimental data are available for this region. The numerical codes which have been developed, and are being used to design systems at SLAC, BNL, Duke, LBL, CEBAF, LANL and UCLA among others, contain our best theoretical understanding of these systems. This paper analyses the present simulation capabilities for short wavelength designs. We discuss how codes are used to design these new systems, which aspects of our models are well implemented and which are not, methods of verifying the models, comparison with experiment, and finally comments on extrapolating to short wavelengths. (26 References).
keywords:
Download | Details | Edit | Delete
title: On the condition for a single bunch high frequency fast blow-up
format: conference proceeding
conference: HEACC 1980 11th
year: 1980
2 authors: J.M. Wang | C. Pellegrini
abstract: The authors study the longitudinal stability of a single particle bunch in a storage ring using Vlasov equation. They show that the Vlasov equation has solutions corresponding to a fast, microwave instability if a condition on the beam current, qualitatively similar to the stability condition for a coasting beam, is satisfied. This condition can be used to define a threshold current, and to discuss its dependence on the longitudinal coupling impedance. (14 References).
keywords:
Download | Details | Edit | Delete
title: Second generation beatwave experiments at UCLA
format: conference proceeding
conference: ICFA Second Generation Plasma Acceleration Workshop
year: 1998
5 authors: C. E. Clayton | C. Joshi | K. A. Marsh | C. Pellegrini | J.B. Rosenzweig
abstract: The NEPTUNE laboratory, under construction at UCLA, will be a user facility for exploring concepts useful for advanced accelerators. The primary programmatic goal for the laboratory is to inject extremely high-quality electron bunches into a laser-driven plasma beat wave accelerator and explore ideas for extracting a high-quality Delta E/E<0.1, epsilon <10 pi mm mrad, high-energy (100 MeV) beam from a plasma structure operating at about 1 THz and about 3 GeV/m. The lab will combine an upgraded MARS CO_2 laser and the state-of-the-art SATURNUS RF gun and linac, also undergoing an upgrade. The new MARS laser will be about 1 TW (100 J, 100 ps), up from 0.2 TW (70 J, 350 ps). This allows for doubling the spot size of the laser beam and thereby quadrupling the interaction length while still driving gradients of 3 GeV/m. The large diameter of the accelerating structure relative to the injected electron bunches (10:1 ratio) will minimize the deleterious effects of the radial dependence of the accelerating field and soften the radial focusing thus permitting, in principle, the extraction of a high-quality accelerated beam.
keywords:
Download | Details | Edit | Delete
title: Performance characteristics, optimization, and error tolerances of a 4 nm FEL based on the SLAC linac
format: conference proceeding
conference: PAC 1993
year: 1993
5 authors: K. J. Kim | M. Xie | E. T. Scharlemann | C. Pellegrini | G. Travish
abstract: A 4 nm free electron laser (FEL) operating in Self Amplified Spontaneous Emission (SASE), and using the SLAC linac as a driver has been extensively studied using the FRED3D and TDA3D codes. Using a 7 GeV beam with a normalized RMS emittance of 3 mm-mrad and a peak current of 2500 A, obtained by longitudinal bunch compression, the FEL can provide about 20 GWatt of peak power, in a subpicosecond pulse. The FEL saturation length is about 60 m. Strong focusing in both planes is provided throughout the undulator by a FODO quadrupole system. We have studied the system gain, its optimization and FEL tolerance to beam parameter changes, wiggler errors and misalignments. (14 References).
keywords:
Download | Details | Edit | Delete
title: The UCLA high gain infrared FEL
format: conference proceeding
conference: FEL 1994 16th
year: 1995
4 authors: G. Travish | M. Hogan | C. Pellegrini | J.B. Rosenzweig
abstract: The particle beam physics laboratory (PBPL) at UCLA is constructing a short period FEL which will operate in the high gain regime. The focus of the work has been the production of a high brightness electron beam suitable for short wavelength FELs. Once operational the FEL will be used to study phenomena of significance to short wavelength devices such as SASE and performance sensitivity to various beam parameters. Future studies may include the addition of a second undulator or amplification of an input source (CO/sub 2/ laser) to study saturation, superradiance, and optical guiding. (11 References).
keywords:
Download | Details | Edit | Delete
title: Bunch length measurement of picosecond electron beams from a photoinjector using coherent transition radiation
format: conference proceeding
conference: ICFA Second Generation Plasma Acceleration Workshop
year: 1998
6 authors: A. Murokh | J.B. Rosenzweig | M. Hogan | Suk, H. | G. Travish | U. Happek
abstract: The bunch length of an electron beam derived from the UCLA Saturnus photoinjector has been measured using a 45 degrees CTR foil. The sudden change of electrons boundary conditions cause them to radiate (transition radiation) with the spectral power entirely dependent upon the degree of coherency, which strongly relates to the beam size. A polarizing Michelson interferometer allowed measurement of the auto-correlation of the coherent transition radiation signal. An analysis method was developed to compensate for undetected low-frequency radiation and systematically extract the bunch length information for a specific beam model. This analysis allowed observation of pulse lengthening due to the space charge, as well as compression with the variation of the RF injection phase. The hypothesis of a satellite beam has been also tested using this analysis. (8 References).
keywords:
Download | Details | Edit | Delete
title: Extended version of an S-band RF gun
format: conference proceeding
conference: PAC 1993
year: 1993
2 authors: S. Park | C. Pellegrini
abstract: A 4.5 MeV RF gun has been in operation at UCLA as a part of a 20 MeV linac. To improve the photoelectron beam parameters without changing the major characteristics of the driving laser and RF systems, a revised and extended version of the present RF gun has been investigated. The new gun consists of 6 full cells terminated at either end by one half cell each. The gun operates in pi -mode at 2.856 GHz. Accelerating fields and mode structures have been studied, and based on this, particle dynamics has been simulated. An aluminum prototype has been built for cold tests. Description of the gun is presented along with initial computational and experimental results. (10 References).
keywords:
Download | Details | Edit | Delete
title: HOMDYN study for the LCLS RF photo-injector
format: conference proceeding
conference: ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams 2nd
year: 2000
5 authors: M. Ferrario | Clendenin, J. E. | D. T. Palmer | J.B. Rosenzweig | L. Serafini
abstract: We report the results of a recent beam dynamics study, motivated by the need to redesign the LCLS photoinjector, that led to the discovery of a new effective working point for a split RF photoinjector. The HOMDYN code, the main simulation tool adopted in this work, is described together with its recent improvements. The new working point and its LCLS application is discussed. Validation tests of the HOMDYN model and low emittance predictions, 0.3 mm-mrad for a 1 nC flat top bunch, are performed with respect to the multi-particle tracking codes ITACA and PARMELA. (26 References).
keywords:
Download | Details | Edit | Delete
title: Parametric study of an X-ray FEL
format: conference proceeding
conference: FEL 1994 16th
year: 1995
7 authors: G. Travish | W. M. Fawley | K. J. Kim | H. D. Nuhn | C. Pellegrini | H. Winick | M. Xie
abstract: An FEL utilizing a high energy, high current and low emittance beam to produce radiation shorter than 2 angstroms is investigated in this paper. This device is an extension of the previously proposed 40 AA Linac Coherent Light Source based on the Stanford linear accelerator. Here we investigate the performance characteristics and parameter sensitivities of this single pass, high gain FEL amplifier operating by self-amplified spontaneous emission (SASE). We begin by comparing various approaches to this short wavelength source and justify our choice of a helical undulator operating on the fundamental frequency. Numerical simulations as well as extensions of previous studies are used to show performance as a function of undulator parameters, startup noise, emittance, focusing, current and energy spread. Further studies and parameter modifications are proposed where needed.
keywords:
Download | Details | Edit | Delete
title: Characterization of plasma accelerators with RF linac terminology
format: conference proceeding
conference: ICFA Second Generation Plasma Acceleration Workshop
year: 1998
3 authors: A. Ogata | J.B. Rosenzweig | M. Ferrario
abstract: The physics of plasma acceleration is described by using RF linac terminology such as shunt impedance, filling time, transit time factor, etc. It is shown that some differences between conventional RF accelerators and plasma accelerators make it difficult to import the RF linac terminology directly into the new field. For example, the shunt impedance is of limited use and the filling time is no use in wake-field accelerators with single-drive beams or single-pump pulses. The beatwave accelerator, a driven oscillator system, has in a sense more similarity to RF linacs than wake-field accelerators. It was shown that plasma wave decay due to collisions and modulational instability seriously deteriorate the quality factor. (26 References).
keywords:
Download | Details | Edit | Delete
title: Initial operation and beam characteristics of the UCLA S-band RF photo-injector
format: conference proceeding
conference: PAC 1993
year: 1993
10 authors: C. Pellegrini | N. Barov | S. C. Hartman | S. Park | J.B. Rosenzweig | G. Travish | R. Zhang | P. Davis | C. Joshi | G. Hairapetian
abstract: The UCLA RF photo-injector system has been commissioned. All of the sub-components such as the high power RF, pico-second laser, RF photo-injector cavity, diagnostics, and supporting hardware have been tested and are operational. We briefly discuss the performance of the various components since the details of each subsystem are very lengthy. The laser delivers a sub 4 ps pulse containing 0-300 mu J of energy per pulse. The photo-injector produces 0-3 nC per bunch with an RF induced emittance of 1.5 pi (mm-mrad). (5 References).
keywords:
Download | Details | Edit | Delete
title: Single crystal copper photo-cathode in the BNL/SLAC/UCLA 1.6 cell RF gun
format: conference proceeding
conference: ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams 2nd
year: 2000
3 authors: D. T. Palmer | S. Anderson | J.B. Rosenzweig
abstract: Previous experimental measurements in the two dimensional (2D) variation of the quantum efficiency, QE, of a polycrystalline copper photo-cathode have measured a 25% variation in this quantity. Two possible causes of this 2D QE variation are contamination of the photo-emitting surface and the work function variation of copper due to crystal facet orientation. We report on the progress to eliminate the 2D QE variation due to the non-uniform crystal facet orientation of copper photo-emitters. This is accomplished by replacing the polycrystalline photo-emitter region of the cathode plane in a modified version of the BNL/SLAC/UCLA 1.6 cell rf gun with a thin disk of a single crystal copper Cu_100. In this paper we present a theoretical discussion on the effect that the crystal structure orientation of a photo-emitter has on the 2D QE. The manufacturing process used in the construction of the single crystal Cu_100 photo-cathode used in these photo-emission experiments are discussed. Preliminary experimental results are presented along with a discussion of our future experimental plans.
keywords:
Download | Details | Edit | Delete
title: Effects of undulator interruptions on the performance of high-gain FEL amplifiers
format: conference proceeding
conference: FEL 1995 17th
year: 1996
3 authors: K.J. Kim | Xie, M. | C. Pellegrini
abstract: The construction as well as the operation of a long undulator required for short wavelength generation with high-gain free-electron lasers will become easier if the undulator could be interrupted with drift sections every few gain lengths. To evaluate the effect of such interruption on the FEL performance, we study the following three effects; (i) the diffraction loss, (ii) the free space slippage and (iii) the phase de-coherence. The effect (i) is found to be small, the effect (ii) gives a condition on the length of the drift section and the effect (iii) is small, but not negligible. (3 References).
keywords:
Download | Details | Edit | Delete
title: The Neptune photoinjector
format: conference proceeding
conference: ICFA Second Generation Plasma Acceleration Workshop
year: 1998
12 authors: J.B. Rosenzweig | S. Anderson | K. Bishofberger | X. Ding | A. Murokh | C. Pellegrini | Suk, H. | A. Tremaine | C. Clayton | C. Joshi | Marsh, K. | P. Muggli
abstract: The RF photoinjector in the Neptune advanced accelerator laboratory, along with associated beam diagnostics, transport and phase-space manipulation techniques are described. This versatile injector has been designed to produce short-pulse electron beams for a variety of uses: ultra-short bunches for injection into a next-generation plasma beatwave acceleration experiment, space-charge dominated beam physics studies, plasma wake-field acceleration driver, plasma lensing, and free-electron laser microbunching techniques. The component parts of the photoinjector, the RF gun, photocathode drive laser systems, booster linac, RF system, chicane compressor, beam diagnostic systems, and control system, are discussed. The present status of photoinjector commissioning at Neptune is reviewed, and proposed experiments are detailed. (33 References).
keywords:
Download | Details | Edit | Delete
title: RF Focusing Effects and Multi-bunch Beam Breakup in Superconducting Linear Colliders
format: conference proceeding
conference: PAC 1993
year: 1993
3 authors: J.B. Rosenzweig | S. Hartman | Stevens, J.
abstract: A high gradient standing wave linear accelerator provides axisymmetric transverse focusing due to the presence of strong alternating gradient transverse electromagnetic fields arising from the backward rf wave. This effect is second order in both the field amplitude and in gamma(-1), so it is of importance only for high gradient, relatively low energy beams. The purpose of the present analysis is to examine the effect of this focusing on multi-bunch beam breakup in a superconducting linear collider, which has both a high accelerating gradient and long bunch train. As an interesting test case, we discuss the beam breakup problem in the TESLA test bed at DESY.
keywords:
Download | Details | Edit | Delete
title: Plasma electron trapping and acceleration in a plasma wake field using a density transition
format: conference proceeding
conference: ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams 2nd
year: 2000
4 authors: Suk, H. | N. Barov | J.B. Rosenzweig | E. Esarey
abstract: A new scheme for plasma electron injection into an acceleration phase of a plasma wake field is presented. In this scheme, a short single electron beam bunch is sent through an underdense plasma with a sharp downward density transition and some plasma electrons are trapped in the plasma wake field due to the rapid wavelength increase of the wake wave at the density transition. To investigate the trapping and acceleration mechanism, two-dimensional particle-in-cell (PIC) simulations were performed, and the illustrative 2-D simulation shows that the new injection method can produce a relatively large charge (~0.5 nC), short (~1 ps) and high energy (> driving beam energy) electron beam pulse with a plasma density transition from 5x10(13) cm(-3) to 3.5x10(13) cm(-3). In addition to the 2-D simulations, 1-D analytic work based on the Hamiltonian formalism and 1D simulations have been performed and the results are also presented. Finally, a proposed experiment at the Neptune Laboratory of UCLA is described.
keywords:
Download | Details | Edit | Delete
title: Towards a plasma wake-field acceleration-based linear collider
format: conference proceeding
conference: ICFA Second Generation Plasma Acceleration Workshop
year: 1998
5 authors: J.B. Rosenzweig | N. Barov | A. Murokh | E. Colby | P. Colestock
abstract: A proposal for a linear collider based on an advanced accelerator scheme, plasma wake-field acceleration in the extremely nonlinear regime, is discussed. In this regime, many of the drawbacks associated with preservation of beam quality during acceleration in plasma are mitigated. The scaling of all beam and wake parameters with respect to plasma wavelength is examined. Experimental progress towards high-gradient acceleration in this scheme is reviewed. We then examine a linear collider based on staging of many modules of plasma wake-field accelerator, all driven by a high average current, pulse compressed, RF photoinjector-fed linac. Issue of beam lending, efficiency, optimized stage length, and power efficiency are discussed. A proof-of-principle experimental test of the staging concept at the Fermilab test facility is discussed.
keywords:
Download | Details | Edit | Delete
title: Design of a High Brightness RF Photoinjector for the SLAC Linac Coherent Light Source
format: conference proceeding
conference: PAC 1993
year: 1993
2 authors: J.B. Rosenzweig | L. Serafini
abstract: The electron injector for the SLAC Linear Coherent Light Source[l] (LCLS) must produce a low jitter, high brightness beam. This beam must be accelerated and longitudinally compressed to yield a sub-picosecond beam which radiates a burst of self-amplified spontaneous emission xrays upon passing through a long undulator. As the gain of this amplifier is very sensitive to the emittance, energy spread and peak current the electron source and subsequent transport, acceleration, and compression systems must reproducibly give a very high quality beam. The conceptual design of an rf photocathode gun which satisfies the requirements of the LCLS is presented here. While the design peak current emitted by this gun is above 200 A, the requirements of gain length in the undulator are such that the beam must undergo longitudinal compression to raise the peak current by an order of magnitude. This compression is very much dependent on both the phase of the accelerating rf wave and the longitudinal wake-fields in the linac, and so the final bunch length will not be reproducible if the time of beam emission (laser beam injection) and/or the charge per bunch have large variations. Because of concerns on reliability and feasibility of the photoinjector, a design which takes maximum advantage of proven technology, and recent experience in photoinjector development has been explored, and is outlined below.
keywords:
Download | Details | Edit | Delete
title: Characterizing The Electron Beam For The Aps Leutl Free Electron Laser
format: conference proceeding
conference: ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams 2nd
year: 2000
3 authors: G. Travish | J. W. Lewellen | M. W. Hahne
abstract: The Advanced Photon Source (APS) Low-Energy Undulator Test Line (LEUTL) project was originally intended to test and characterize advanced undulator designs via electron beambased diagnostics technique. It is presently being used to conduct free electron laser (FEL) research for a future fourth-generation light source. The APS injector linac has been upgraded to deliver a beam suitable for these FEL tests. The project has as an initial goal the operation of a self amplified spontaneous emission (SASE) device operating in the visible at 530 nm (green light). The visible FEL requires a 217 MeV moderately high brightness beam with a peak current of 100 A or greater, a normalized rms emittance of 5 ?m or less, and an energy spread of 0.1% or better. Beam characterization is fundamental to being able to match experimental results with theoretical models. This paper describes the LEUTL FEL, lists the major goals, the beam diagnostics, and presents the initial electron beam measured properties. Future plans are also discussed.
keywords:
Download | Details | Edit | Delete
title: Research and development toward a 4.5-1.5 angstrom linac coherent light source (LCLS) at SLAC
format: conference proceeding
conference: FEL 1995 17th
year: 1996
32 authors: R. Tatchyn | J. Arthur | M. Baltay | K. Bane | R. Boyce | M. Cornacchia | T. Cremer | A. Fisher | S. J. Hahn | M. Hernandez | G. Loew | R. Miller | W. R. Nelson | H. D. Nuhn | D. Palmer | J. Paterson | T. Raubenheimer | J. Weaver | H. Wiedemann | H. Winick | C. Pellegrini | G. Travish | E. T. Scharlemann | S. Caspi | W. Fawley | K. Halbach | K. J. Kim | R. Schlueter | M. Xie | D. Meyerhofer | R. Bonifacio | L. De Salvo
abstract: In recent years significant studies have been initiated on the feasibility of utilizing a portion of the 3 km S-band accelerator at SLAC to drive a short wavelength (4.5-1.5 Angstrom) Linac Coherent Light Source (LCLS), a Free-Electron Laser (FEL) operating in the Self-Amplified Spontaneous Emission (SASE) regime. Electron beam requirements for single-pass saturation in a minimal time include: 1) a peak current in the 7 kA range, 2) a relative energy spread of <0.05%, add 3) a transverse emittance, epsilon [rad-m], approximating the diffraction-limit condition epsilon=lambda/4 pi, where lambda[m] is the output wavelength. Requirements on the insertion device include field error levels of 0.02% for keeping the electron bunch centered on and in phase with the amplified photons, and a focusing beta of 8 m/rad for inhibiting the dilution of its transverse density. Although much progress has been made in developing individual components and beam-processing techniques necessary for LCLS operation down to similar to 20 Angstrom, a substantial amount of research and development is still required in a number of theoretical and experimental areas leading to the construction and operation of a 4.5-1.5 Angstrom LCLS. In this paper we report on a research and development program underway and in planning at SLAC for addressing critical questions in these areas. These include the construction and operation of a linac test stand for developing laser-driven photocathode rf guns with normalized emittances approaching 1 mm-mrad; development of advanced beam compression, stability, and emittance control techniques at multi-GeV energies; the construction and operation of a FEL Amplifier Test Experiment (FATE) for theoretical and experimental studies of SASE at IR wavelengths; an undulator development program to investigate superconducting, hybrid/permanent magnet (hybrid/PM), and pulsed-Cu technologies; theoretical and computational studies of high-gain FEL physics and LCLS component designs; development of X-ray optics and instrumentation for extracting, modulating, and delivering photons to experimental users; and the study and development of scientific experiments made possible by the source properties of the LCLS.
keywords:
Download | Details | Edit | Delete
title: HIGH EFFICIENCY, HIGH BRIGHTNESS X-RAY FREE ELECTRON LASERS VIA FRESH BUNCH SELF-SEEDING
format: conference proceeding
conference: IPAC 2016
year: 2016
6 authors: C. Emma | C. Pellegrini | A. Lutman | M. Guetg | A. Marinelli | J. Wu
abstract: High efficiency, terawatt peak power X-ray Free Electron Lasers (XFELs) are a promising tool for enabling 3D atomic resolution single molecule imaging and nonlinear science using X-ray beams. Increasing the efficiency of XFELs while maintaining good longitudinal coherence can be achieved via self-seeding and tapering the undulator magnetic field. The efficiency of tapered self seeded XFELs is limited by two factors: the ratio of seed power to beam energy spread and the ratio of seed power to electron beam shot noise. We present a method to overcome these limitations by producing a strong X-ray seed and amplifying it with a small energy spread electron bunch. This can be achieved by selectively suppressing lasing for part of the electron beam in the SASE section and using the rest of the bunch to generate the seed radiation. In this manner one can reach saturation with the seeding electrons and the strong seed pulse can be overlapped with the “fresh" electrons downstream of the self-seeding monochromator. Simulations of this scenario demonstrating an increased efficiency are presented for two systems, an optimal superconducting undulator design and the Linac Coherent Light Source. In the case of the LCLS we examine how the betatron oscillations leading to selective suppression can be induced by using the transverse wakefield of a parallel plate corrugated structure, a dechirper.
keywords:
Download | Details | Edit | Delete
title: Injection and dynamics of accelerated beams
format: conference proceeding
conference: ICFA Second Generation Plasma Acceleration Workshop
year: 1998
1 author: J.B. Rosenzweig
abstract: This paper is a summary of the discussions undertaken by the working group on injection and accelerated beam dynamics at the 1st ICFA novel and advanced accelerator workshop on second generation plasma accelerators. The second generation of work on plasma accelerators is aimed to bring the accelerated beams up to the quality needed for applications such as high-energy physics linear colliders. To begin, first generation, or proof-of-principle, experiments and concepts were reviewed. To map the work needed in the second generation of development, the demands of the applications were examined, and an improved framework for discussing the viability of plasma accelerators was constructed. In particular, the issues scaling applications to the short wavelengths characteristic of plasma accelerators was discussed, as was the appropriate characterization of the beam quality in these devices, and the connection between plasma accelerator and conventional accelerator design. Within this framework, the working group discussed electron sources and injectors, the effects of drive beam evolution on accelerated beam dynamics, this effects of nonlinear plasma wave fields on beam phase space, stochastic processes, spatial and temporal beam-plasma wave matching, and future second-generation experimental goals and techniques.
keywords:
Download | Details | Edit | Delete
title: Design of a high duty cycle, asymmetric emittance RF photocathode injector for linear collider applications
format: conference proceeding
conference: PAC 1993
year: 1993
4 authors: J.B. Rosenzweig | E. Colby | C. Jackson | Nicol, T.
abstract: One of the attractive features of the superconducting approach to linear collider design is that the transverse emittances demanded are much larger than in normal conducting schemes. For TESLA design parameters, the damping rings appear to be relatively large and expensive, and it is therefore of some interest to look into alternative sources. For electrons, a promising source candidate is an RF photocathode. In this paper, we present conceptual design work towards development of an asymmetric emittance RF photocathode source which can operate at the TESLA repetition rates and duty cycle, and is capable of emitting beams with the required emittances and charge per pulse. (7 References).
keywords:
Download | Details | Edit | Delete
title: Nonequilibrium transverse motion and emittance growth in space-charge dominated beams
format: conference proceeding
conference: ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams 2nd
year: 2000
2 authors: S. Anderson | J.B. Rosenzweig
abstract: The transverse dynamics of space-charge dominated beams are investigated both analytically and computationally, in order to understand the mechanisms for emittance oscillations and growth due to nonlinear space-charge fields. This work explores the role of space-charge dominated equilibrium and its relationship to phase space wave-breaking, which is responsible for the irreversible emittance growth in these systems. The physics of both coasting and accelerating beams are examined, in order to illuminate the most effective approaches to beam handling during the emittance compensation process, as well as during subsequent beam transport. (13 References).
keywords:
Download | Details | Edit | Delete
title: TDA3D: Updates and improvements to the widely used three-dimensional free electron laser simulation
format: conference proceeding
conference: FEL 1996 18th
year: 1997
7 authors: B. Faatz | W. Fawley | P. Pierini | Sven Reiche | G. Travish | D. Whittum | J. Wurtele
abstract: TDA3D is a widely distributed and often used Free Electron Laser (FEL) simulation code. While a number of versions of TDA exist, this paper describes the official version which is well tested and supported. We describe the capabilities of the code emphasizing recent improvements and revisions. TDA3D is a steady-state (time-independent) amplifier code. The code self-consistently solves, after averaging over a wiggler period, the paraxial wave equation for the radiation field and the Lorentz equations of motion for the electrons. The paraxial wave equation includes diffraction and optical guiding. The calculation of the electron beam motion takes into account longitudinal bunching and transverse betatron oscillations, so that emittance, energy spread, and external focusing can be properly modeled. Recent additions to the simulation include the ability to model natural wiggler focusing in one or both planes, alternating gradient quadrupoles or sextupoles, and ion channels. The initial loading of the electron distribution can be controlled to allow for matching into focusing channels, improved quiet starts (non-correlated phase-space distributions), and arbitrary energy spread.
keywords:
Download | Details | Edit | Delete
title: An X-ray transition radiation beam profile detector for the LCLS
format: conference proceeding
conference: ICFA Workshop on Nonlinear and Collective Phenomena in Beam Physics
year: 1999
2 authors: S. Monteiro | C. Pellegrini
abstract: We discuss the characteristics of a transverse beam profile detector for a high energy charged particle accelerator, and propose a candidate detector based on transition radiation in the X-ray region of the spectrum. The detector is useful for low emittance, high energy beams, for example, the LCLS electron beam. We expect that it can resolve spatial details as small as a few microns. The advantages of this method over previous ones are that the measurements are linear with the beam density and the results are a point by point map of the beam density. (14 References).
keywords:
Download | Details | Edit | Delete
title: Status of the variable momentum compaction storage ring experiment in SPEAR
format: conference proceeding
conference: PAC 1993
year: 1993
11 authors: Tran, P. | A. Amiry | C. Pellegrini | Corbett, J. | M. Cornacchia | Lee, M. | Nuhn, H. D. | H. Winick | Wu, D. | Hofmann, A. | D. Robin
abstract: Variable momentum compaction lattices have been proposed for electron-positron colliders and synchrotron radiation sources to control synchrotron tune and bunch length. To address questions of single particle stability limits, a study has been initiated to change the SPEAR lattice into a variable momentum compaction configuration for experimental investigation of the beam dynamics. In this paper, we describe a model-based method used to transform SPEAR from the injection lattice to the low momentum compaction configuration. Experimental observations of the process are reviewed. (12 References).
keywords:
Download | Details | Edit | Delete
title: Use of an inverse free electron laser in a linear collider B factory
format: conference proceeding
conference: AAC 1992 3rd
year: 1993
3 authors: C. Pellegrini | J. Sandweiss | N. Barov
abstract: The authors examine the possibility of using an IFEL as an accelerator in a linear collider B Factory. An IFEL is able to utilize a sizeable fraction of the energy of the laser pulse used to accelerate the beams. It is also able to meet the stringent requirements imposed on the energy spread and luminosity at the interaction point. Two separate examples are considered, differing in the way the laser pulse energy is coupled to the electron beam. The first maximizes the slippage between the beam bunch and the radiation, in order to decrease the peak laser power. In the second example the slippage is minimized. This results in uniform beam loading and may in principle be run at higher efficiency and lower average power. The authors also address the laser required to drive this accelerator. The power and frequency requirements suggest the use of a FEL drive laser. The design for this system includes the use of superconducting cavities to accelerate the drive beam, which is then propagated through an initially constant period undulator that is tapered after saturation.
keywords:
Download | Details | Edit | Delete
title: The UCLA high gain infrared free electron laser
format: conference proceeding
conference: FEL 1996 18th
year: 1997
5 authors: M. Hogan | C. Pellegrini | J.B. Rosenzweig | G. Travish | A. A. Varfolomeev
abstract: A high gain SASE FEL amplifier designed to operate in the infrared (near 10 mu m) is being commissioned in the particle beam physics laboratory at UCLA. The high brightness beam needed to drive the FEL is provided by an RF photocathode gun employing solenoidal emittance compensation. A novel linac (a plane wave transformer) accelerates the beam to a final energy [left angle bracket]or=15 MeV. This beam is to be sent through a 60 cm long undulator with a period of 1.5 cm and an undulator parameter K approximately=1. Near future experiments will focus on FEL physics relevant to proposed short wavelength devices. Investigations of start-up from noise (SASE), effects of beam parameters on gain as well as noise fluctuations are of particular interest. Here we present an overview of the hardware including relevant diagnostics, measured beam parameters, FEL simulation results and the status of proposed experiments. (9 References).
keywords:
Download | Details | Edit | Delete
title: Energy Loss of a High Charge Bunched Electron Beam in Plasma: Analysis
format: conference proceeding
conference: ICFA Workshop on Physics and Applications of High Brightness Electron Beams
year: 2003
3 authors: N. Barov | J.B. Rosenzweig | M.C. Thompson
abstract: There has been much interest in the blowout regime of plasma wakefield acceleration (PWFA), which features ultra-high fields and nonlinear plasma motion. Using an exact analysis, we examine here a fundamental limit of nonlinear PWFA excitation, by an infinitesimally short, relativistic electron beam. The beam energy loss in this case is shown to be linear in charge even for nonlinear plasma response, where a normalized, unitless charge exceeds unity. The physical basis for this effect is discussed, as are deviations from linear behavior observed in simulations with finite length beams.
keywords:
Download | Details | Edit | Delete
title: Numerical studies of strong focusing in planar undulators
format: conference proceeding
conference: PAC 1993
year: 1993
2 authors: G. Travish | J.B. Rosenzweig
abstract: The present trend towards short wavelength operation with long undulators places tight requirements on the electron beam quality and hence the need to maintain a well focused beam. This paper examines the performance of alternating gradient (AG) sextupole focusing in planar undulators. Numerical simulation results of free electron laser performance using AG sextupole focusing are compared to results using only natural focusing and to those using quadrupole focusing. (10 References).
keywords:
Download | Details | Edit | Delete
title: A 2-4 nm Linac Coherent Light Source (LCLS) using the SLAC linac
format: conference proceeding
conference: PAC 1993
year: 1993
20 authors: H. Winick | K. Bane | R. Boyce | G. Loew | P. Morton | H. D. Nuhn | J. Paterson | P. Pianetta | T. Raubenheimer | J. Seeman | R. Tatchyn | V. Vylet | C. Pellegrini | J.B. Rosenzweig | G. Travish | D. Prosnitz | E. T. Scharlemann | K. Halbach | K. J. Kim | M. Xie
abstract: We describe the use of the SLAC linac to drive a unique, powerful, short wavelength Linac Coherent Light Source (LCLS). Operating as an FEL, lasing would be achieved in a single pass of a high peak current electron beam through a long undulator by self-amplified spontaneous emission. The main components are a high-brightness rf photocathode electron gun; pulse compressors; about 1/5 of the SLAC linac; and a long undulator with a FODO quadrupole focusing system. Using electrons below 8 GeV, the system would operate at wavelengths down to about 3 nm, producing [right angle bracket]or=10 GW of peak power in sub-ps pulses. At a 120 Hz rate the average power is approximately=1 W. (6 References).
keywords:
Download | Details | Edit | Delete
title: New design study and related experimental program for the LCLS RF photoinjector
format: conference proceeding
conference: EPAC 2000
year: 2000
11 authors: M. Ferrario | P.R. Bolton | Clendenin, J. E. | Dowell, D. H. | Gierman, S. M. | M. E. Hernandez | D. C. Nguyen | D. T. Palmer | J.B. Rosenzweig | Schmerge, J. F. | L. Serafini
abstract: We report the results of a recent beam dynamics study, motivated by the need to redesign the LCLS photoinjector, that lead to the discovery of a new effective working point for a split RF photoinjector. We consider the emittance compensation regime of a space charge beam: by increasing the solenoid strength, the emittance evolution shows a double minimum behavior in the drifting region. If the booster is located where the relative emittance maximum and the envelope waist occur, the second emittance minimum can be shifted to the booster exit and frozen at a very low level (0.3 mm-mrad for a 1 nC flat top bunch), to the extent that the invariant envelope matching conditions are satisfied. Standing Wave Structures or alternatively Traveling Wave Structures embedded in a Long Solenoid are both candidates as booster linac. A careful measurement of the emittance evolution as a function of position in the drifting region is necessary to verify the computation and to determine experimentally the proper position of the booster cavities. The new design study and supporting experimental program under way at the SLAC Gun Test Facility are discussed.
keywords:
Download | Details | Edit | Delete
title: IFEL experiment at Neptune Lab
format: conference proceeding
conference: EPAC 2000
year: 2000
2 authors: P. Musumeci | C. Pellegrini
abstract: We present a two stage Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Lab. Proof-of-principle experiments on the IFEL scheme have been carried out successfully. This experiment is intended to achieve a 100 MeV energy gain, staging two IFEL modules. It will use a 16 MeV electron beam, a 1 TW CO2 laser and two different tapered helical undulators. The problem of refocusing both laser and electron beam is analysed in detail. A preliminary beam-line layout and numerical simulations are presented.
keywords:
Download | Details | Edit | Delete
title: Highlights of AAC 2000 Workshop
format: conference proceeding
conference: Linear Accelerator Conference 2000
year: 2000
1 author: J.B. Rosenzweig
abstract: The Advanced Accelerator Concepts 2000 (AAC2K) Workshop was held in Santa Fe in June, 2000, and included a wide array of conceptual and theoretical advances at the frontier of accelerator physics. This paper reviews the highlights of the workshop, with subjects ranging from acceleration using lasers, plasmas and microstructures, to the beam physics of muon colliders. Particular emphasis is given to the topics which are relevant to research at existing linear accelerator facilities, and the effect of this research on the capabilities of such facilities.
keywords:
Download | Details | Edit | Delete
title: Upgrade of the simulation code TDA3D
format: conference proceeding
conference: FEL 1998 20th
year: 1999
2 authors: Sven Reiche | B. Faatz
abstract: The well-known Free Electron Laser (FEL) amplifier simulation code TDA3D has been upgraded to include most of the important features needed for present and future design studies of VUV and X-ray single-pass FELs. A number of bugs have been removed and I/O has been changed and extended to make it more flexible. To features such as wiggler errors, quadrupole misalignment has been added and corrector coils to adjust the beam trajectory. In addition, multi-section undulators can now be simulated with arbitrary (integrated or separated) focusing structures.
keywords:
Details | Edit | Delete
title: High-Brightness Beams from a Light Source Injector: The Advanced Photon Source Low-Energy Undulator Test Line Linac
format: conference proceeding
conference: Linear Accelerator Conference 2000
year: 2000
9 authors: G. Travish | S. Biedron | M. Borland | M. W. Hahne | K. C. Harkay | J. Lewellen | A. Lumpkin | S. Milton | N. S. Sereno
abstract: The use of existing linacs, and in particular light source injectors, for free-electron laser (FEL) experiments is becoming more common due to the desire to test FELs at ever shorter wavelengths. The high-brightness, highcurrent beams required by high gain FELs impose technical specifications that most existing linacs were not designed to meet. Moreover, the need for specialized diagnostics, especially shot-to-shot data acquisition, demands substantial modification and upgrade of conventional linacs. Improvements have been made to the Advanced Photon Source (APS) injector linac in order to produce and characterize high brightness beams. Specifically, effort has been directed at generating beams suitable for use in the low-energy undulator test line (LEUTL) FEL in support of fourth-generation light source research. The enhancements to the linac technical and diagnostic capabilities that allowed for self-amplified spontaneous emission (SASE) operation of the FEL at 530 nm are described. Recent results, including details on technical systems improvements and electron beam measurement techniques, will be discussed. The linac is capable of accelerating beams to over 650 MeV. The nominal FEL beam parameters used are as follows: 217 MeV energy; 0.1-0.2% rms energy spread; 4-8 um normalized rms emittance; 80-120 A peak current from a 0.2-0.7 nC charge at a 2-7 ps FWHM bunch.
keywords:
Download | Details | Edit | Delete
title: TM01 Mode Launcher for use in High Brightness Photoguns
format: conference proceeding
conference: IPAC 2016
year: 2016
3 authors: A. Cahill | M. Dal Forno | V.A. Dolgashev
abstract: Photo rf guns are a source of electron beams for X-ray FELs such as LCLS and European XFEL. In existing photo-guns power is coupled into the cavity by rectangular waveguides through the cell walls, [1], or use coaxial coupling, [2]. We are considering feeding a gun using a circular waveguide with the TM01 mode. To do that we need a mode launcher, a matched device that couples the rectangular TE01 mode waveguide to a TM01 mode in a circular waveguide. Use of the mode launcher reduces complexity of the gun cavity and increases flexibility of positioning the input waveguide relative to the gun body. Mode launchers have been successfully used at SLAC and elsewhere for X-band high gradient tests. Because the existing mode launchers were not built for high brightness rf guns, they have a significant quadrupole field component. High brightness rf guns have tight requirements on output beam properties. The quadrupole component of the mode launcher adversely affects the beam quality. We have designed a mode launcher free of this disadvantage. We present an example S-band mode launcher with minimized quardupole field component.
keywords:
Download | Details | Edit | Delete
title: Measured free-electron laser microbunching using coherent transition radiation
format: conference proceeding
conference: FEL 1998 20th
year: 1999
9 authors: A. Tremaine | J.B. Rosenzweig | S. Anderson | Pedro Frigola | M. Hogan | A. Murokh | C. Pellegrini | D. C. Nguyen | Sheffield, R.
abstract: The microbunch distribution of an electron beam exiting a SASE free-electron laser has been measured using the emitted coherent transition radiation (CTR) produced from a thin aluminum foil placed at the end of the undulator. The wavelength of the coherent transition radiation is shown to be the same as the FEL wavelength, and thus a measure of the beam microbunch spacing. Also, the study of the CTR linewidth and angular acceptance of the radiation captured are shown to be derived from this coherent radiative process. Scattering effects on the forward emitted transition radiation from the electron beam traversing an aluminum foil are also considered. (11 References).
keywords:
Download | Details | Edit | Delete
title: Measuring FEL radiation properties at VISA-FEL
format: conference proceeding
conference: PAC 2001
year: 2001
25 authors: A. Murokh | R. Agustsson | Pedro Frigola | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | A. Tremaine | M. Babzien | I. Ben-Zvi | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X. J. Wang | K. A. Van Bibber | L. Bertolini | J. M. Hill | G.P. Le Sage | M. Libkind | A. Toor | R. Carr | M. Cornacchia | L. Klaisner | H. D. Nuhn | Ruland, R.
abstract: The VISA (Visible to Infrared SASE Amplifier) SASE free electron laser has been successfully operated at the Accelerator Test Facility (ATF) at BNL. High gain and saturation were observed at 840 nm. We describe here the diagnostic system, experimental procedures and data reduction algorithms, as the FEL performance was measured along the length of the undulator. We also discuss selected spectral radiation measurements. (10 References).
keywords:
Download | Details | Edit | Delete
title: A diagnostic system to measure SASE-FEL radiation properties along the 4-meter VISA undulator
format: conference proceeding
conference: FEL 1999 21st
year: 2000
4 authors: A. Murokh | E. Johnson | J.B. Rosenzweig | A. Tremaine
abstract: During the last several years there has been a great experimental effort in the developing high gain SASE free electron lasers. Single pass FEL gain of 10 5 was achieved in the far infrared [ 1 ]. The research is directed towards smaller wavelengths and yet higher gain, with the ultimate goal of constructing the x-ray FEL [ 2 ]. A number of experiments are under the development to demonstrate SASE at visible and UV range. However, many important properties of the process of self-amplified spontaneous emission are still to be verified experimentally. As a part of the VISA experimental program (visible-to-infrared SASE amplifier [ 3 , 4 ]), we have constructed a diagnostics system, which will allow a detailed characterisation of the FEL process along the 4 meters of VISA undulator.
keywords:
Download | Details | Edit | Delete
title: Commissioning of the UCLA PEGASUS Photoinjector Laboratory
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: S. Telfer | Sven Reiche | J.B. Rosenzweig | Pedro Frigola | G. Andonian
abstract: The PEGASUS Photoinjector has been commissioned at UCLA. The Plane Wave Transformer Photoinjector provides a high-brightness 17 MeV beam that will be used for numerous beam-radiation studies. Some of these will include SASE FEL, transition radiation from non-standard surfaces, and monochromatic x-ray production via PXR and Thompson scattering.
keywords:
Download | Details | Edit | Delete
title: Multi-dimensional free-electron laser simulation codes: a comparison study
format: conference proceeding
conference: FEL 1999 21st
year: 2000
8 authors: S. G. Biedron | Y. C. Chae | R. J. Dejus | B. Faatz | H. P. Freund | S. V. Milton | H. D. Nuhn | Sven Reiche
abstract: A self-amplified spontaneous emission (SASE) free-electron laser(FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.
keywords:
Download | Details | Edit | Delete
title: Commissioning of the Neptune photoinjector
format: conference proceeding
conference: PAC 2001
year: 2001
9 authors: S. Boucher | Burke, A. | Loh, M. | P. Musumeci | J.B. Rosenzweig | M.C. Thompson | S. Anderson | R. Agustsson | R. J. England
abstract: The status of the RF photoinjector in the Neptune advanced accelerator laboratory is discussed. The components of the photoinjector: the RF gun and booster linac, chicane compressor, and beam diagnostic systems are described. Measurement techniques used to diagnose the short pulse length, high brightness beam are detailed and measurements of emittance and pulse compression are given. The effect of the pulse compressor on transverse emittance is explored. (11 References).
keywords:
Download | Details | Edit | Delete
title: High power femtosecond pulses from an X-ray SASE-FEL
format: conference proceeding
conference: FEL 1999 21st
year: 2000
1 author: C. Pellegrini
abstract: We discuss how to use the large-gain bandwidth of an X-ray SASE-FEL to produce femtosecond long pulses by chirping and compressing the output FEL radiation. We consider the power level, spectral width, and intensity fluctuations of the compressed X-ray pulse compared to the case with no compression. (9 References).
keywords:
Download | Details | Edit | Delete
title: Compensation of FEL gain reduction by emittance effects in a strong focusing lattice
format: conference proceeding
conference: FEL 1999 21st
year: 2000
1 author: Sven Reiche
abstract: As the constraint of a small transverse emittance becomes more severe, the higher the electron beam energy in an FEL. To compensate for the transverse and thus the longitudinal velocity spread. a compensation scheme has been proposed previously by Derbenev and Sessler et al., for Free Electron Lasers by introducing a correlation between the energy and the average betatron amplitude of each electron. This compensation scheme is based on a constant absolute value of the transverse velocity, a feature of the natural focusing of undulators. and does not include strong focusing of a superimposed quadrupole lattice. This paper focuses on the electron motion in a strong focusing lattice with a variation in the axial velocity. The resulting reduction of the compensation efficiency is analyzed using simulations. It is seen that the compensation scheme is not much affected if the lattice cell length is shorter than the gain length. For the results presented in this paper, the parameters of the proposed TESLA X-ray FEL have been used.
keywords:
Download | Details | Edit | Delete
title: Emittance measurements of the space charge dominated Thomson source photoinjector
format: conference proceeding
conference: PAC 2001
year: 2001
4 authors: S. Anderson | J.B. Rosenzweig | G.P. Le Sage | J. Crane
abstract: The photocathode rf gun test facility in Livermore National Laboratory's Thomson source is described. The quadrupole scan and slit based emittance measurement techniques are used to measure the emittance of the space charge dominated beam. Experimental results are compared with simulation and theoretical calculations. (10 References).
keywords:
Download | Details | Edit | Delete
title: A method for measuring the FEL radiation power along an undulator
format: conference proceeding
conference: FEL 1999 21st
year: 2000
1 author: Sven Reiche
abstract: A highly desirable measurement in Free Electron Laser (FEL) experiments is the dependency of the radiation power along the undulator. Most designs of undulators prohibit detection of the radiation power within the undulator or extracting the electron beam at arbitrary positions. Transport of both, the radiation field and the electron beam, through the entire undulator, and thus an ongoing FEL interaction, is unavoidable. If there are many correction magnets distributed along the beam pipe, one can think of exciting a large orbit distortion downstream from any of these correctors. For a gain length comparable to or larger than the beta function this excitation of a coherent betatron oscillation might degrade the FEL amplification to a level, for which the radiation power does not further grow over the remaining length of the undulator. This paper presents the efficiency of this method for the parameters of the VUV FEL at the TESLA Test Facility.
keywords:
Download | Details | Edit | Delete
title: Ultra high-gradient energy loss by a pulsed electron beam in a plasma
format: conference proceeding
conference: PAC 2001
year: 2001
9 authors: N. Barov | K. Bishofberger | J.B. Rosenzweig | J.P. Carneiro | P. Colestock | H. Edwards | Fitch, M. J. | W. Hartung | J. Santucci
abstract: The plasma wake-field mechanism can be used to couple energy at a high rate from a bunched electron beam into a plasma wave. We will present results from the Fermilab A0 facility where a beam with an initial energy of 14 MeV passes through the plasma to emerge with a much broader energy spread, spanning from a low of 3 MeV to a high of over 20 MeV. Over the 8 cm length of the 10(14) cm(-3) plasma, this implies a 140 MeV/m deceleration and 72 MeV/m acceleration gradient. (12 References).
keywords:
Download | Details | Edit | Delete
title: Simulation of time-dependent energy modulation by wake fields and its impact on gain in the VUV free electron laser of the TESLA Test Facility
format: conference proceeding
conference: FEL 1999 21st
year: 2000
2 authors: Sven Reiche | H. Schlarb
abstract: For shorter bunches and narrower undulator gaps the interaction between the electrons in the bunch and the wake fields becomes so large that the FEL amplification is affected. For a typical vacuum chamber of an X-ray or VUV Free Electron Laser three major sources of wake fields exist: a resistance of the beam pipe, a change in the geometric aperture and the surface roughness of the beam pipe. The generated wake fields, which move along with the electrons, change the electron energy and momentum, depending on the electron longitudinal and transverse position. In particular, the accumulated energy modulation shifts the electrons away from the resonance condition. Based on an analytic model the energy loss by the wake fields has been incorporated into the time-dependent FEL simulation code GENESIS 1.3. For the parameters of the TESLA Test Facility the influence of the bunch length, beam pipe diameter and surface roughness has been studied. The results are presented in this paper.
keywords:
Download | Details | Edit | Delete
title: Investigations of electron-beam microbunching and beam coalignment using CTR in a high-gain SASE FEL
format: conference proceeding
conference: PAC 2001
year: 2001
11 authors: A. Lumpkin | W. Berg | S. Biedron | M. Borland | Y. C. Chae | R. Dejus | J. Lewellen | S. Milton | E. Moog | G. Travish | B. Yang
abstract: We recently extended our experiments on z-dependent electron-beam microbunching using coherent transition radiation (CTR) into the high-gain, self-amplified spontaneous emission free-electron laser (FEL) regime. The UV-visible FEL at the Advanced Photon Source was operated at 530 nm and 385 nm using the bunch-compressed photocathode gun electron beam, linac, and 21.6 m of undulator length. The longitudinal microbunching of the electron beam was tracked by inserting a metal foil and a mirror after each of the nine 2.4-m-long undulators. The visible CTR generated by the electron-beam interaction was imaged and analyzed for z-dependent intensity, angular distribution, and spot size. Additionally, the image centroids and structures were used in evaluating the critical electron beam/photon beam overlap issue as a complement to the trajectory data from the beam position monitors. (9 References).
keywords:
Download | Details | Edit | Delete
title: Status and initial commissioning of a high gain 800 nm SASE FEL
format: conference proceeding
conference: FEL 1999 21st
year: 2000
22 authors: A. Tremaine | Pedro Frigola | A. Murokh | P. Musumeci | C. Pellegrini | J.B. Rosenzweig | M. Babzien | Ben-Zvi, I. | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X.J. Wang | Yu, L. H. | Van Bibber, K. A. | J.M. Hill | G.P. Le Sage | R. Carr | M. Cornacchia | Nuhn, H. D. | Ruland, R. | D. C. Nguyen
abstract: We describe the status and initial commissioning of the visible to infrared SASE amplifier (VISA) experiment. VISA uses a strong focusing 4 m undulator, the Brookhaven National Laboratory ATF linac with an energy of 72 MeV, and a photoinjector electron source. The VISA fundamental radiation wavelength is near 800 nm and the power expected at saturation is near 60 MW. Power, angular and spectral measurements are planned for the VISA radiation and these results will be analyzed and compared with SASE FEL theory and computer simulation. In addition, the induced electron beam micro-bunching will be measured using coherent transition radiation. (12 References).
keywords:
Download | Details | Edit | Delete
title: Design Considerations for a High-Efficiency High-Gain Free-Electron Laser for Power Beaming
format: conference proceeding
conference: FEL 2003 25th
year: 2003
2 authors: C. Muller | G. Travish
abstract: Power beaming from ground-based systems to space-based platforms has been proposed by a number of researchers as a means of delivering energy to orbiting satellites and stations. This paper considers the use of a seeded high-gain high-efficiency Free-Electron Laser (FEL) amplifier based on a conventional linac as the source for power beaming. While the wall-plug efficiency of a single pass FEL is likely to be considerably lower than a recirculating system, electrical efficiency is unlikely to be a serious consideration for first-generation power-beaming systems. Moreover, the simplicity of the proposed scheme scales well from existing and completed experiments.
keywords:
Download | Details | Edit | Delete
title: The Drive Laser for the APS LEUTL FEL RF Photoinjector
format: conference proceeding
conference: FEL 1999 21st
year: 2000
3 authors: G. Travish | N. D. Arnold | R. J. Koldenhoven
abstract: The APS LEUTL free-electron laser (FEL) is a high-gain, short-wavelength device requiring a high-current, low-emittance beam. An rf photoinjector driven by a laser is used to provide the requisite beam. The drive laser consists of a diode-pumped Nd:Glass oscillator and a chirped pulse amplification (CPA) system consisting of a grating stretcher, a flashlamp-pumped Nd:Glass regenerative amplifier, and a grating compressor. The system generates 4-mJ pulses in the IR with a pulse length as short as 2 ps FWHM and a repetition rate of 6 Hz. Nonlinear doubling crystals are used to generate fourth-harmonic output of ~500 uJ in the UV (263 nm), which is required to exceed the work function of the copper cathode in the gun. This paper describes the drive laser as well as the extensive controls implemented to allow for remote operation and monitoring. Performance measurements as well as the operating experience are presented.
keywords:
Download | Details | Edit | Delete
title: Introduction to the physics of the free electron laser
format: conference proceeding
conference: Joint US-CERN School of Particle Accelerators: Frontiers of Particle Beams
year: 1988
2 authors: J.B. Murphy | C. Pellegrini
abstract: The authors explore the basic physics of the FEL, emphasizing the underlying physical principles with a minimum of mathematics. The description is based on the classical theory of the FEL as that is sufficient to explain most of the physics. The elementary principles of operation of an FEL and the trajectory of an electron in the magnetic field of both helical and planar undulator magnets are presented. The trajectories are then used to calculate the spontaneous emission of an electron in an undulator magnet. The electron equations of motion are extended to include the forces due to both the undulator and the radiation field. If the change in the radiation field is small in one pass through the undulator, one can compute the so-called 'small signal gain' of the FEL using only the particle equations of motion; the radiation field is assumed to remain constant. The potential for increasing the efficiency of an FEL by tapering the period and magnetic field strength of the undulator magnet is discussed.
keywords:
Download | Details | Edit | Delete
title: Short wavelength FELs on large storage rings
format: conference proceeding
conference: National Conference on Synchrotron Radiation Instrumentation 7th
year: 1992
6 authors: H. D. Nuhn | R. Tatchyn | H. Winick | A.S. Fisher | J.C. Gallardo | C. Pellegrini
abstract: The use of a large-circumference, high-energy, electron-positron collider such as PEP, TRISTAN or PETRA to drive a free-electron laser (FEL), producing high levels of coherent power at short wavelengths around 40 AA is explored. The authors consider self-amplified spontaneous emission (SASE), in which electron bunches with low emittance, high peak current and small energy spread radiate coherently in a single pass through a long undulator. As the electron beam passes down the undulator, its interaction with the increasingly intense spontaneous radiation causes a bunch density modulation at the optical wavelength, resulting in stimulated emission and exponential growth of coherent power in a single pass. The need for optical-cavity mirrors, which place a lower limit on the wavelength of a conventional FEL oscillator, is avoided. Various combinations of electron-beam and undulator parameters, as well as special undulator designs, are discussed. Saturation and high peak, in-band, coherent power (460 MW) are possible with a 67 m, hybrid permanent-magnet undulator in a ring bypass. A 100 m, cusp-field undulator can achieve high average, in-band, coherent power (0.25 W) in the main ring. The existing, 25.6 m Paladin undulator at LLNL, with the addition of optical-klystron dispersive sections, is considered for both peak and average power.
keywords:
Download | Details | Edit | Delete
title: Velocity bunching experiment at the Neptune Laboratory
format: conference proceeding
conference: ICFA Workshop on Physics and Applications of High Brightness Electron Beams
year: 2003
3 authors: P. Musumeci | R. Yoder | J.B. Rosenzweig
abstract: In this paper we describe the rectilinear compression ex- periment at the Neptune photoinjector at UCLA. The elec- tron bunches have been shortened to sub-ps pulse length by chirping the beam energy spectrum in a short S-band high gradient standing wave RF cavity and then letting the elec- trons undergo velocity compression in the following rec- tilinear drift. Using a standard Martin Puplett interferom- eter to characterize coherent transition radiation from the beam, we measured bunch lengths as short as 0.4 ps with compression ratio in excess of 10 for an electron beam of 7 MeV energy and charge up to 300 pC.
keywords:
Download | Details | Edit | Delete
title: Trapping of background plasma electrons in a beam-driven plasma wake field using a downward density transition
format: conference proceeding
conference: AAC 2000 9th
year: 2001
4 authors: Suk, H. | N. Barov | J.B. Rosenzweig | E. Esarey
abstract: Trapping of background plasma electrons by a beam-driven plasma wake field is studied as a new self-injection method. In this scheme, a short electron beam pulse is sent through an underdense plasma with a downward density transition and some background plasma electrons are trapped by the strong wake field due to the sudden increase of the wake wave wavelength at the density transition. Two-dimensional PIC (Particle-In-Cell) simulations show that a significant amount of plasma electrons are trapped and accelerated to a higher energy than the driving beam energy. Furthermore, the trapped-beam quality is fairly good. In this paper, the 2-D simulation results, dynamics of the trapped beam and the driving beam, and the proposed experiment for the UCLA Neptune Laboratory are described. (15 References).
keywords:
Download | Details | Edit | Delete
title: Preliminary conceptual design for a 510 MeV electron/positron injector for a UCLA phi factory
format: conference proceeding
conference: PAC 1991
year: 1991
4 authors: G. Dahlbacka | Hartline, R. | W. Barletta | C. Pellegrini
abstract: UCLA (University of California at Los Angeles) is proposing a compact superconducting high-luminosity (10(32-33)/ cm(-2)/ s(-1)) e+ e- collider for a phi factory. To achieve the required e+ e- currents, full energy injection from a linac with intermediate storage in a positron accumulator ring (PAR) is used. The elements of the linac are outlined with cost and future flexibility in mind. The preliminary conceptual design starts with a high current gun similar in design to those developed at SLAC and at ANL (for the APS). Four 4-section linac modules follow, each driven by a 60-MW klystron with a 1- mu s macropulse and an average current of 8.6 A. The first 4-section module is used to create positrons in a tungsten target at 186 MeV. The remaining three modules are used to accelerate the e+ e- beam to 558 MeV (no load limit) for injection into the PAR. (0 References).
keywords:
Download | Details | Edit | Delete
title: Plasma Wakefield Experiments
format: conference proceeding
conference: AAC 2002 10th
year: 2002
6 authors: N. Barov | M.C. Thompson | K. Bishofberger | J.B. Rosenzweig | H. Edwards | J. Santucci
abstract: We discuss the recent experiments in the field of Plasma Wakefield Acceleration (PWFA), with emphasis on the FNAL experiment. After completion of this work, the next round of experiments will need to push the envelope on accelerating gradient, interaction length, stability, and accelerated charge. We present theoretical results dealing with plasma accelerator performance in the limit of high driver charge, and short wavelengths. We comment on the impact of such results on both the afterburner (single module) and staged (multiple modules) approaches to plasma-based accelerators.
keywords:
Download | Details | Edit | Delete
title: Synchrotron radiation problems in storage ring version of FEL
format: conference proceeding
conference: ONR Workshop on Free-Electron Generators of Coherent Radiation 2nd
year: 1980
1 author: C. Pellegrini
abstract: The main properties of synchrotron radiation are reviewed. A semi-qualitative description is given of how synchrotron radiation determines the beam emittance in an electron storage ring and the importance of this for free electron laser operation. (9 References).
keywords:
Download | Details | Edit | Delete
title: Production and synchronization of electron beams from RF photoinjector/compressor systems for ultra-fast applications
format: conference proceeding
conference: AAC 2000 9th
year: 2001
2 authors: M.C. Thompson | J.B. Rosenzweig
abstract: The RF photoinjector, when coupled with a magnetic pulse compression system, is now an ubiquitous tool for production of sub-picosecond electron beam pulses which are to be used in advanced accelerator and light source experiments. As the time-scale for both pulse lengths and synchronization to external systems approaches the femtosecond level, a clear understanding of the longitudinal dynamics of the electron injector is required. This paper presents an analysis of the longitudinal beam dynamics of electron bunches in the photoinjector/compressor system from birth at the photocathode, through their initial violent acceleration in the RF gun, and subsequent phase space manipulation in the post-acceleration linac and magnetic chicane. The phenomena of phase focusing due to RF forces, and defocusing due to longitudinal space-charge, are discussed, as is the process of magnetic pulse compression. The issues relevant to synchronization of electron pulses with external lasers are examined, using the examples of beat-wave acceleration and Compton light sources, and solutions involving appropriate compressor configurations are proposed. Diagnosis of the relevant physical effects in such schemes is discussed.
keywords:
Download | Details | Edit | Delete
title: Saturnus: the UCLA infrared free-electron laser project
format: conference proceeding
conference: PAC 1991
year: 1991
17 authors: J. W. Dodd | S. C. Hartman | S. Park | C. Pellegrini | J.B. Rosenzweig | Smolin, J. A. | G. Hairapetian | J. Kolonko | W. Barletta | D.B. Cline | J. G. Davis | C. J. Joshi | N. Luhmann | S. N. Ivanchenkov | A. S. Khlebnikov | Lachin, Y. Y. | A. A. Varfolomeev
abstract: A compact 20-MeV linac with an RF laser-driven electron gun will be used to drive a high-gain (10-cm gain length), 10.6- mu m wavelength FEL (free-electron laser) amplifier, operating in the SASE mode. Saturnus will mainly be used to study FEL physics in the high-gain regime, including start-up from noise, optical guiding, sidebands, saturation, and superradiance, with emphasis on the effects important for future short-wavelength operation of FELs. The primary magnetic flux is provided by C-shaped iron yokes, where between the poles thin blocks of neodymium-iron-boron magnets are placed to provide additional magnetic flux along the undulator axis. (9 References).
keywords:
Download | Details | Edit | Delete
title: Single beam coherent instabilities in circular accelerators and storage rings
format: conference proceeding
conference: Summer School on High Energy Particle Accelerators
year: 1981
1 author: C. Pellegrini
abstract: The author discusses the meaning of coherent instabilities and illustrates the techniques that can be used to study this problem. He considers a particle and introduces the equations of motion for the case of longitudinal and transverse coherent oscillations. An expression for the longitudinal and transverse coherent is derived forces. There forces are then used in the Vlasov equations to obtain a dispersion relation and define the limiting conditions for stability. The longitudinal and transverse stabilities are discussed. (25 References).
keywords:
Details | Edit | Delete
title: Three dimensional simulation of high harmonic transverse optical klystron
format: conference proceeding
conference: FEL 1987 9th
year: 1988
4 authors: S.K. Dutt | Friedman, A. | A. Gover | C. Pellegrini
abstract: We present the results of a three dimensional simulation code, which calculates the parameters of coherent super-radiant harmonic frequency emission by electrons which are being bunched by an external laser beam while propagating in a planar undulator. This code was written in order to simulate the TOK experiment, which is presently underway at BNL. Instead of a full numerical simulation of Maxwell's equations and the electron force equations, a semi-analytical approach is adopted. Electron trajectories are computed analytically, and the radiation fields are expanded in terms of free space eigenmodes. Phase space and energy profiles of the electron beam are incorporated by a variable space sampling according to a given distribution function, rather than via Monte Carlo simulation. Computation time of about 0.1 s/electron was achieved with the present version of the code on the IBM 3090. We present the expected radiometric parameters as a function of the electron beam parameters (emittance and energy spread), and the modulating laser beam parameters (Rayleigh length, waist position and power). Statistical averaging is carried out by weighted averaging of the initial electron moments and energy phase space distribution. This approach results in the best prediction of the expected experimental measurement of the optical parameters which can be achieved with a finite number of sampling electrons (much smaller than in the experiment), without introducing artificial noise as in the Monte Carlo approach.
keywords:
Download | Details | Edit | Delete
title: Conceptual Design of a High Luminosity 510 MeV Collider
format: conference proceeding
conference: PAC 1991
year: 1991
3 authors: C. Pellegrini | M. Cornacchia | D. Robin
abstract: We discuss the magnetic lattice design of a high luminosity 510 MeV electron-positron collider, based on high field superconduction bending dipoles. The design criteria are flexibility in the choice of the tune and beta functions at the interaction point, horizontal emittance larger than 1 mm mrad to produce a luminosity larger than 10(32) cm(-2)s(-1), large synchrotron radiation damping rate, and large momentum compaction. The RF system parameter are chosen to provide a short bunch length also when the beam energy spread is determined by the microwave instability. A satisfactory ring dynamic aperture, and a simultaneous small value of the horizontal and vertical beta function at the interaction point, we expect will be achieved by using Cornacchia Halbach modified sextupoles.
keywords:
Download | Details | Edit | Delete
title: Velocity bunching experiment at the Neptune Laboratory
format: conference proceeding
conference: AAC 2002 10th
year: 2002
5 authors: P. Musumeci | R. J. England | M.C. Thompson | R.B. Yoder | J.B. Rosenzweig
abstract: In this paper we describe the ballistic bunching compression experiment at the Neptune photoinjector at UCLA. We have compressed the beam by chirping the beam energy spectrum in a short S-band high gradient standing wave RF cavity and then letting the electrons undergo velocity compression in the subsequent rectilinear drift. Using a standard Martin Puplett interferometer for coherent transition radiation measurement, we have observed bunch length as short as 0.4 ps with compression ratio in excess of 10 for an electron beam of 7 MeV and charge up to 0.3 nC. We also measured slice transverse emittance via quad scan technique. The observed emittance growth agrees with the predictions and the simulations. Extension of this scheme to a future advanced accelerator injector system where solenoidal magnetic field can compensate the emittance growth is studied.
keywords:
Download | Details | Edit | Delete
title: Report of the working group on far field accelerators
format: conference proceeding
conference: Workshop on the Laser Acceleration of Particles
year: 1982
1 author: C. Pellegrini
abstract: This report describes the work of the group on far field accelerators. The work concentrated on two accelerator schemes, the inverse free electron laser and the two wave device. The possibilities and limitations of these two accelerators are discussed, as well as some of the requirements on the laser necessary to reach very high energies. A conceptual design of a single pass inverse free electron laser is presented. (10 References).
keywords:
Download | Details | Edit | Delete
title: Progress toward a soft X-ray FEL
format: conference proceeding
conference: FEL 1987 9th
year: 1988
1 author: C. Pellegrini
abstract: Reviews the FEL physics and obtains scaling laws for the extension of its operation to the soft X-ray region. The author also discusses the properties of an electron beam needed to drive such an FEL, and the present state of the art for the beam production. (17 References).
keywords:
Download | Details | Edit | Delete
title: Electron density enhancement in a quasi isochronous storage ring
format: conference proceeding
conference: PAC 1991
year: 1991
2 authors: C. Pellegrini | D. Robin
abstract: Conditions are established for stable single particle motion in a storage ring with very small momentum compaction, and very short bunch length, the quasi isochronous ring. How this condition can be achieved is discussed. Applications of this condition to colliders and synchrotron radiation sources is examined. (2 References).
keywords:
Download | Details | Edit | Delete
title: Plasma Density Transition Trapping as a Possible High-Brightness Electron Beam Source
format: conference proceeding
conference: AAC 2002 10th
year: 2002
2 authors: J.B. Rosenzweig | M.C. Thompson
abstract: Plasma density transition trapping is a recently proposed self-injection scheme for plasma wakefield accelerators. This technique uses a sharp downward plasma density transition to trap and accelerate background plasma electrons in a plasma wakefield. This paper examines the quality of electron beams captured using this scheme in terms of emittance, energy spread, and brightness. Two-dimensional particle-in-cell simulations show that these parameters can be optimized by manipulating the plasma density profile.We also develop, and support with simulations, a set of scaling laws that predicts how the brightness of transition trapping beams scales with the plasma density of the system. These scaling laws indicate that transition trapping can produce beams with brightness 5 1014 A= mrad 2. A proof-ofprinciple transition trapping experiment is planned for the near future. The proposed experiment is described in detail.
keywords:
Download | Details | Edit | Delete
title: A high brightness electron accelerator and its particle beam physics. Experimental program
format: conference proceeding
conference: INFN International School on Electromagnetic Radiation and Particle Beams Acceleration
year: 1989
1 author: C. Pellegrini
abstract: Reviews the main characteristics of the Accelerator Test Facility (ATF), and gives a short discussion of the experimental program to be carried out with it. This program will utilize the unique possibility offered by the ATF, of providing a high brightness electron bunch, synchronized with high power laser pulses. Part of the program will be based on the study of the interaction between the laser radiation and the electrons, in particular laser acceleration of particle beams, and the nonlinear dynamics of electrons in a strong electromagnetic field. Another part will utilize the high brightness of the electron beam to study the physics of free electron lasers in the high gain regime, with the aim of establishing a basis for the development of FELs in the soft X-ray region. (14 References).
keywords:
Details | Edit | Delete
title: Non-equilibrium transverse motion and emittance growth in space-charge dominated beams
format: conference proceeding
conference: APS April Meeting
year: 2000
2 authors: S. Anderson | J.B. Rosenzweig
abstract: The transverse dynamics of space-charge dominated beams are investigated both analyitically and computationally, in order to understand the mechanisms for emittance oscillations and growth due to nonlinear space-charge fields. This work explores the role of space-charge dominated equilibrium and its relationship to phase space wave-breaking, which is responsible for the irreversible emittance growth in these systems. The physics of both coasting and accelerating beams are examined, in order to illuminate the most effective approaches to beam handling during the emittance compensation process, as well as during subsequent beam transport.
keywords:
Download | Details | Edit | Delete
title: A high luminosity superconducting mini collider for phi meson production and particle beam physics
format: conference proceeding
conference: PAC 1991
year: 1991
14 authors: C. Pellegrini | D. Robin | D. B. Cline | J. Kolonko | S. Anderson | W. Barletta | Chargin, A. | M. Cornacchia | Dalbacka, G. | K. Halbach | Lueng, E. | Kimball, F. | Madura, D. | Patterson, L.
abstract: A 510-MeV electron-positron collider has been proposed at the University of California at Los Angeles to study particle beam physics and phi-meson physics at luminosities larger than 1032 cm/sup -2/s/sup -1/. The collider consists of a single compact superconducting storage ring (SMC), with a bending field of 4 T and a current larger than 1 A. A discussion is presented of the main characteristics of this system and its major technical components: superconducting dipoles and the RF vacuum and injection systems. (6 References).
keywords:
Download | Details | Edit | Delete
title: A Resonant, THz Slab-Symmetric Dielectric-Based Accelerator
format: conference proceeding
conference: AAC 2002 10th
year: 2002
2 authors: R. B. Yoder | J.B. Rosenzweig
abstract: Slab-symmetric dielectric-loaded structures, consisting of a vacuum gap between dielectric-lined conducting walls, have become a subject of interest for short-wavelength acceleration due to their simplicity, relatively low power density, and advantageous beam dynamics. Such a structure can be resonantly excited by an external power source and is known to strongly suppress transverse wakefields. Motivated by the prospect of a high-power FIR radiation source, currently under construction at UCLA, we investigate a high-gradient slab- symmetric accelerator powered by up to 100 MW of laser power at 340 um, with a predicted gradient near 100 MeV/m. Three-dimensional simulation studies of the structure fields and wakes are presented and compared with theory, and a future experiment is discussed.
keywords:
Download | Details | Edit | Delete
title: Commissioning of the Neptune Photoinjector
format: conference proceeding
conference: APS April Meeting
year: 2000
13 authors: S. Anderson | J.B. Rosenzweig | Burke, A. | X. Ding | Loh, M. | P. Musumeci | C. Pellegrini | Suk, H. | M.C. Thompson | C. Clayton | C. Joshi | Marsh, K. | P. Muggli
abstract: The status of the commissioning of the rf photoinjector in the Neptune advanced accelerator laboratory is discussed. The component parts of the photoinjector, the rf gun, photocathode drive laser system, booster linac, rf system, chicane compressor, beam diagnostics systems, and control system are described. Recent improvements in the rf gun, rf timing, and chicane compressor systems are detailed. This injector is designed to produce short pulse length, high brightness electron beams. Experiments planned for the immediate future are described. Initial measurements of various beam parameters are presented.
keywords:
Download | Details | Edit | Delete
title: Flat-beam RF photocathode sources for linear collider applications
format: conference proceeding
conference: PAC 1991
year: 1991
1 author: J.B. Rosenzweig
abstract: Laser-driven RF photocathodes represent a recent advance in high-brightness electron beam sources. The author investigates a variation on these devices that was obtained by using a ribbon laser pulse to illuminate the cathode, yielding a flat beam ( sigma /sub x/[right angle bracket][right angle bracket] sigma /sub y/) which has asymmetric emittances at the cathode proportional to the beam size in each transverse dimension. The flat-beam geometry mitigates space charge forces which lead to intensity-dependent transverse and longitudinal emittance growth, thus limiting the beam brightness. The fundamental limit on achievable emittance and brightness is set by the transverse momentum distribution and peak current density of the photoelectrons. (11 References).
keywords:
Download | Details | Edit | Delete
title: Electron Beam Production and Characterization for the PLEIADES Thomson X-Ray Source
format: conference proceeding
conference: AAC 2002 10th
year: 2002
13 authors: W. J. Brown | F. V. Hartemann | A. Tremaine | P. T. Springer | G.P. Le Sage | C. P. J. Barty | J.B. Rosenzweig | J. K. Crane | R. R. Cross | D. N. Fittinghoff | D. J. Gibson | D. R. Slaughter | S. Anderson
abstract: We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. Simulations of beam production, transport, and focus are presented. It is shown that a 1 ps, 500 pC electron bunch with a normalized emittance of less than 5 Tcmm-mrad can be delivered to the interaction point. Initial electron measurements are presented. Calculations of expected x-ray flux are also performed, demonstrating an expected peak spectral brightness of 1020 photons/s/mm2/mrad2/0.1% bandwidth. Effects of RF phase jitter are also presented, and planned phase measurements and control methods are discussed.
keywords:
Download | Details | Edit | Delete
title: Free electron lasers: development and applications
format: conference proceeding
conference: HEACC 1989 14th
year: 1990
1 author: C. Pellegrini
abstract: The author gives an overview of the FEL status and applications; discusses some of the work being done for its further development, in particular in the soft X-ray region. (69 References).
keywords:
Download | Details | Edit | Delete
title: Initial operation of S-band plane wave transformer photoinjector
format: conference proceeding
conference: APS April Meeting
year: 2000
4 authors: X. Ding | C. Pellegrini | J.B. Rosenzweig | S. Telfer
abstract: An integrated S-Band RF photoinjector based on the plane wave transformer (PWT) is being built and operated in the Particle Beam Physics Laboratory at UCLA. This novel structure integrates a photocathode directly into a PWT Linac making the structure simple and compact. Due to the strong coupling between each adjacent cell, this structure is relatively easy to fabricate and operate. This photoinjector can provide high brightness beams at energies of 15 to 20MeV, with emittance less than 1mm-mrad at charge of 1 nC. These short-pulse beams can be used in various applications: space charge dominated beam physics studies, plasma lenses, plasma accelerators, free-electron laser microbunching techniques, and SASE-FEL physics studies. It will also provide commercial opportunities in chemistry, biology and medicine. The initial operation of the PWT photoinjector with high RF power is described. A comparation of experimental result and theoretical design is also discussed.
keywords:
Details | Edit | Delete
title: Transverse equilibria in linear collider beam-beam collisions
format: conference proceeding
conference: PAC 1991
year: 1991
2 authors: J.B. Rosenzweig | Chen, P.
abstract: An analytical model of the equilibrium approached by the beams, that of a generalized Bennett pinch which develops through collisionless damping due to the strong nonlinearity of the beam-beam interaction is presented. In order to calculate the equilibrium pinched beam size, an estimation of the RMS emittance growth is made which takes into account the partial adiabaticity of the collision. This pinched beam size is used to derive the luminosity enhancement factor, whose scaling is in agreement with the simulation results for both D and thermal factor A= sigma /sub z// beta * large, and explains the previously noted cubic relationship between round and flat beam enhancement factors. (4 References).
keywords:
Download | Details | Edit | Delete
title: Longitudinal Beam Shaping and Compression Scheme for the UCLA Neptune Laboratory
format: conference proceeding
conference: AAC 2002 10th
year: 2002
3 authors: R. J. England | J.B. Rosenzweig | M.C. Thompson
abstract: We are developing a new beamline which will serve as a venue for future beam- plasma interaction experiments using the 14MeV electron beam produced by the UCLA Neptune 1.625-cell photoinjector and PWT linac. An examination of the first and second-order optics indicates that when certain nonlinear effects are minimized through the use of sextupole magnets, the longitudinal dispersion is dominated by a negative R 5 6- Simulations using the matrix transport code ELEGANT indicate that for an appropriately chirped initial beam, this beamline can be used to create a ramped picosecond to sub-picosecond beam that is ideal for driving large amplitude wake fields in a plasma and producing high transformer ratios.
keywords:
Download | Details | Edit | Delete
title: Short wavelength FELs based on self amplified spontaneous emission
format: conference proceeding
conference: Conference on Free-Electron Lasers and Applications
year: 1990
1 author: C. Pellegrini
abstract: The experiment will utilize a single electron bunch traversing the undulators. Combining the three undulator parts the author explores the optical klystron and the self amplified spontaneous emission regime, optical guiding and other effects like sidebands instabilities and superradiance. After initial operation they will start a program to improve the beam characteristics using the radiation from the undulator as a diagnostic tool. As the beam quality improves one can also increase the beam energy and reduce the radiation wavelength. (49 References).
keywords:
Download | Details | Edit | Delete
title: Ion clearing by cyclotron resonance shaking
format: conference proceeding
conference: PAC 1991
year: 1991
2 authors: Zhou, P. | J.B. Rosenzweig
abstract: A new concept in ion clearing for storage rings, that of resonant removal of ions in dipoles by shaking the beam horizontally near the ion cyclotron frequency is discussed. This method of beam shaking is similar to the variations on ion bounce shaking but has advantages in requiring a narrower bandwidth of shaking frequencies and in much higher achievable ion kinetic energies. The results of analytical theory, and computer simulations are discussed. (7 References).
keywords:
Download | Details | Edit | Delete
title: High-Brightness Beam Generation and Characterization at the Advanced Photon Source Low-Energy Undulator Test Line Linac
format: conference proceeding
conference: APS April Meeting
year: 2000
9 authors: J. Lewellen | S. Biedron | M. Borland | M. W. Hahne | K. C. Harkay | A. Lumpkin | S. Milton | N. S. Sereno | G. Travish
abstract: Improvements to the Advanced Photon Source injector linac have been made to allow for the production and characterization of high-brightness beams in support of fourth-generation light source research. In particular, effort has been directed at generating beams suitable for use in the low-energy undulator test line (LEUTL) free-electron laser (FEL). We describe the enhancements to the linac operational and diagnostic capabilities that enabled self-amplified spontaneous emission (SASE) operation of the FEL at 530 nm. Electron beam measurement techniques and recent results will be discussed. Beam properties are measured under the same operational conditions as those used for FEL studies. The nominal FEL beam parameters are as follows: 217 MeV beam energy; less than 0.15 mm-mrad normalized emittance; 100 A peak current from a 0.7-nC charge at a 7-psec bunch.
keywords:
Details | Edit | Delete
title: Envelope instability in the Fermilab Booster
format: conference proceeding
conference: PAC 1991
year: 1991
3 authors: Zhou, P. | J.B. Rosenzweig | Stahl, S.
abstract: The transverse emittance in the FNAL (Fermi National Accelerator Laboratory) Booster grows at a high beam intensity, in a time less than 100 turns. An examination is made of the possible contributions to the fast emittance growth from coherent instability of the beam envelope. Theoretical analysis, through the use of envelope equations, is employed to predict the dependence of envelope instability on the peak current of the Booster beam. These predictions are compared to the results of multiparticle tracking calculations. (11 References).
keywords:
Download | Details | Edit | Delete
title: A two stage IFEL accelerator
format: conference proceeding
conference: APS April Meeting
year: 2000
2 authors: P. Musumeci | C. Pellegrini
abstract: We present a two stage Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Lab. Proof-of-principle experiments on the IFEL scheme have been carried out succesfully. This experiment is intended to achieve a 100 Mev energy gain, staging two IFEL modules. It will use the 16 Mev electron beam produced by the Neptune linac, the 1 TW MARS CO2 laser and two different tapered undulators. The problem of refocusing both laser and electron beam is analyzed in detail. A preliminary beamline layout and numerical simulations are presented.
keywords:
Details | Edit | Delete
title: Status of RF photoinjector and PWT linac at UCLA
format: conference proceeding
conference: Linear Accelerator Conference 1992
year: 1992
12 authors: S. Park | N. Barov | S. Hartman | C. Pellegrini | J.B. Rosenzweig | P. Tran | G. Travish | R. Zhang | P. Davis | G. Hairapetian | C. Joshi | N. Luhmann
abstract: The authors report the present status of RF photoinjector and plane wave transformer (PWT) linac for the production of 20 MeV/c electron beam. The photoinjector is a 1/sup 1///sub 2/ cell pi -mode standing wave structure operating at 2.856 GHz with photoelectrons generated on a copper cathode by 4 ps long laser pulse at 206 nm. Measurements of the beam of photoelectrons are underway at various experimental parameters. The PWT has been tested at low power to investigate its mode structure. An overview of the system, latest data, and future directions are presented. (5 References).
keywords:
Details | Edit | Delete
title: Boiling the Vacuum with an X-ray FEL
format: conference proceeding
conference: APS April Meeting
year: 2000
1 author: C. Pellegrini
abstract: We discuss the possibility of producing an electromagnetic field on the order of the Schwinger critical field by focusing the X-ray beam produced by the X-ray free-electron laser, LCLS, under development by a SLAC-ANL-BNL-LANL-UCLA collaboration. We also discuss an experiment which would use this very large field to test QED through the production of electron-positron pairs in vacuum, with no real particles being present in the initial state.
keywords:
Details | Edit | Delete
title: High brightness electron sources
format: conference proceeding
conference: Linear Accelerator Conference 1998
year: 1998
1 author: J.B. Rosenzweig
abstract: The production of unprecedentedly high brightness electron beams is a critical aspect of many applications, from free-electron lasers to advanced accelerators. The preferred method for obtaining these beams is the radiofrequency photoinjector. The physics and technology aspects of this device are reviewed here, along prospects for future progress in high-brightness beam development.
keywords:
Download | Details | Edit | Delete
title: Dielectric Wakefield Accelerating Structure as a Source of Terahertz Coherent Cerenkov Radiation
format: conference proceeding
conference: AAC 2006 12th
year: 2006
8 authors: A.M. Cook | J.B. Rosenzweig | M.C. Thompson | H. Badakov | G. Travish | R. Tikhoplav | O.B. Williams | R. J. England
abstract: We discuss future experimental work proposed to study the performance of a cylindrical dielectric wakefield accelerating structure as a coherent Cerenkov radiation source at the Neptune laboratory at UCLA. The Cerenkov wakefield acceleration experiment carried out recently by UCLA/SLAC/USC, using the ultrashort and high charge beam (Q = 3 nC, RMS bunch length = 20 micron) at the SLAC FFTB, demonstrated electromagnetic wakes at the few GV/m level. The motivation of our prospective experiment is to investigate the operation of a similar scenario using the comparatively long pulse, low charge beam (Q = 0.5 nC, RMS bunch length = 200 micron) at UCLA Neptune. The field amplitude produced in this setup would be one to two orders of magnitude lower, at the few tens to few 100 MV/m level. Such a decelerating field would extract a significant amount of energy from a low-energy beam in a distance on the order of a few centimeters, allowing the use of short dielectric structures. We discuss details of the geometry and composition of the structures to be used in the experiment. We also examine the possibility of a future dedicated facility at UCLA Neptune based on a hybrid photoinjector currently in development. The intrinsic bunch compression capabilities and improved beam parameters (RMS bunch length = 100 micron, Q = 1 nC) of the photoinjector would allow the creation of a high power radiation source in the terahertz regime.
keywords:
Download | Details | Edit | Delete
title: The APS SASE FEL: status and commissioning results
format: conference proceeding
conference: PAC 1999
year: 1999
7 authors: S. V. Milton | S. G. Biedron | P. Den Hartog | J. W. Lewellen | E. Moog | A. Nassiri | G. Travish
abstract: A self-amplified spontaneous emission (SASE) free-electron laser (FEL) is under construction at the Advanced Photon Source (APS). Three gun systems, an rf-test area, laser room, numerous diagnostics, a transfer line at the end of the linac and a new building, which will serve as the experimental hall, have been added. The only remaining items to be installed are the undulators into the beamline. Here, the additions to the APS in support of this project as well as commissioning results and future plans will be discussed. (9 References).
keywords:
Download | Details | Edit | Delete
title: Saturnus: the UCLA high-gain infrared FEL project
format: conference proceeding
conference: FEL 1990 12th
year: 1991
17 authors: F. Aghamir | W. Barletta | D.B. Cline | J. W. Dodd | S. C. Hartman | T.C. Katsouleas | J. Kolonko | S. Park | C. Pellegrini | Terrien, C. | J. G. Davis | C. J. Joshi | N. Luhmann | D. B. McDermott | S. N. Ivanchenkov | Lachin, Y. Y. | A. A. Varfolomeev
abstract: The authors present the status of Saturnus: an infrared FEL operating in the 10 mu m wavelength region, driven by a compact 20 MeV linac with a photoinjector, under construction at UCLA. The 1.5 cm period, 0.5 T peak-field undulator is being built at the Kurchatov IAE. The FEL is being designed to operate primarily in the self-amplified spontaneous emission mode. They plan to study the startup from noise, optical guiding, saturation, sidebands and superradiance, with emphasis on the effects important for future short-wavelength operation of FELs. The photoinjector follows closely the Brookhaven design. Electrons are injected into an accelerating section based on the plane-wave transformer design developed by Swenson at SAIC. Simulation of the linac and FEL show a gain length of 10 cm, and saturation power of 50 MW. (10 References).
keywords:
Download | Details | Edit | Delete
title: Commissioning of the Neptune photoinjector
format: conference proceeding
conference: PAC 1999
year: 1999
21 authors: S. Boucher | P. Musumeci | Loh, M. | Burke, A. | S. Anderson | J.B. Rosenzweig | K. Bishofberger | X. Ding | Holden, T. | A. Murokh | C. Pellegrini | Suk, H. | A. Tremaine | C. Clayton | C. Joshi | Marsh, K. | P. Muggli | M.C. Thompson | S. Anderson | R. Agustsson | R. J. England
abstract: The status of the commissioning of the RF photoinjector in the Neptune advanced accelerator laboratory is discussed. The component parts of the photoinjector, the RF gun, photocathode drive laser system, booster linac, RF system, chicane compressor, beam diagnostics systems, and control system are described. This injector is designed to produce short pulse length, high brightness electron beams. Experiments planned for the immediate future are described. Initial measurements of various beam parameters are presented. (10 References).
keywords:
Download | Details | Edit | Delete
title: Design concepts of a storage ring for a high power XUV free electron laser
format: conference proceeding
conference: FEL 1985 7th
year: 1986
12 authors: M. Cornacchia | J. Bisognano | S. Chattopadhyay | A. Garren | K. Halbach | A. Jackson | K. J. Kim | H. Lancaster | J. Peterson | M. S. Zisman | C. Pellegrini | G. Vignola
abstract: The authors report on the study of a storage ring capable of sustaining an electron beam of the quality required for a high-gain free electron laser in the vacuum ultraviolet and X-ray region. They describe a method for the optimization of the design of the storage ring where several competing and often conflicting requirements come into play. They present an example design of a ring that satisfies the required conditions of beam quality and is able to produce coherent radiation at 400 AA with tens of megawatts of peak power. (11 References).
keywords:
Download | Details | Edit | Delete
title: Proposal for a SASE-Free-electron laser Experiment, VISA, at the ATF Linac
format: conference proceeding
conference: FEL 2000 22nd
year: April 8, 1998
5 authors: UCLA | BNL | LANL | LLNL | SLAC
abstract: We present a proposal of a SASE-FEL experiment, VISA, to be done at the ATF linac unsing a 4m long undulator, to study the FEL collective instability regime, including saturation, start-up, time dependence and spectral and angular characteristics of the radiation. The experiment will use a complete set of diagnostics tools to allow a detailed comparison of the experimental results with the theory and the simulation codes. The experiment is being proposed by the VISA group, BNL-LLNL-LANL-SSRL/SLAC-UCLA collaboration. The experiment is part of a program to demonstrate the feasibility of short wavelength, UV to X-ray, FELs based on teh SASE collective instability regime. This program has received the highest priority from the Birgenau panel, which has recently presented a report to DOE on future needs and development of synchrotron radiation sources in the USA. This top priority has been confirmed by the fact that the Basic Energy Sciences division of DOE has already provided the funding needed to carry our VISA.
keywords:
Details | Edit | Delete
title: The APS SASE FEL: Modeling and code comparison
format: conference proceeding
conference: PAC 1999
year: 1999
8 authors: S. G. Biedron | Y. C. Chae | R. J. Dejus | B. Faatz | H. P. Freund | S. Milton | H. D. Nuhn | Sven Reiche
abstract: A self-amplified spontaneous emission (SASE) free electron laser (FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.
keywords:
Download | Details | Edit | Delete
title: Saturnus: the UCLA compact infrared free-electron laser project
format: conference proceeding
conference: Intense Microwave and Particle Beams II
year: 1991
16 authors: J. W. Dodd | F. Aghamir | W. Barletta | D. B. Cline | S. C. Hartman | T. C. Katsouleas | J. Kolonko | S. Park | C. Pellegrini | P. G. Davis | C. J. Joshi | N. C. Luhmann | D. B. McDermott | S. N. Ivanchenkov | YuYu Lachin | A. A. Varfolomeev
abstract: Saturnus is an infrared FEL operating in the 10 mu m wavelength region, driven by a compact 20 MeV linac with a photoinjector, under construction at UCLA. The 1.5 cm period, 0.6 T peak field undulator is being built at the Kurchatov IAE. The FEL is designed to operate primarily in the self amplified spontaneous emission mode. The authors plan to study the start-up from noise, optical guiding, saturation, sidebands and superradiance, with emphasis on the effects important for future short wavelength operation of FEL's. The photoinjector follows closely the Brookhaven design. Electrons are injected into an accelerating section based on the plane-wave-transformer design developed by Swenson at SAIC. Simulation of the linac and FEL show a gain length of 10 cm, and a saturation power of 50 MW. (13 References).
keywords:
Download | Details | Edit | Delete
title: Generation of High Brightness X-Rays with the PLEIADES Thomson X-Ray Source
format: conference proceeding
conference: PAC 2003
year: 2003
14 authors: W. J. Brown | S. Anderson | C. P. J. Barty | J. K. Crane | R. R. Cross | D. N. Fittinghoff | F. V. Hartemann | J. Kuba | G.P. Le Sage | D. R. Slaughter | P. T. Springer | A. Tremaine | J.B. Rosenzweig | D. J. Gibson
abstract: The use of short laser pulses to generate high peak intensity, ultra-short x-ray pulses enables exciting new experimental capabilities, such as femtosecond pump-probe experiments used to temporally resolve material structural dynamics on atomic time scales. PLEIADES (Picosecond Laser Electron InterAction for the Dynamic Evaluation of Structures) is a next generation Thomson scattering x-ray source being developed at Lawrence Livermore National Laboratory (LLNL). Ultra-fast picosecond x-rays (10-200 keV) are generated by colliding an energetic electron beam (20-100 MeV) with a high intensity, sub-ps, 800 nm laser pulse. The peak brightness of the source is expected to exceed 1020 photons/s/0.1 bandwidth/mm2/mrad2. Simulations of the electron beam production, transport, and final focus are presented. Electron beam measurements, including emittance and final focus spot size are also presented and compared to simulation results. Measurements of x-ray production are also reported and compared to theoretical calculations.
keywords:
Download | Details | Edit | Delete
title: The UCLA compact infrared free-electron laser
format: conference proceeding
conference: FEL 1991 13th
year: 1992
16 authors: J. W. Dodd | S. C. Hartman | S. Park | C. Pellegrini | J.B. Rosenzweig | D.B. Cline | G. Hairapetian | J. Kolonko | Smolin, J. A. | P.G. Davis | C. J. Joshi | N. Luhmann | S. N. Ivanchenkov | A. S. Khlebnikov | A. A. Varfolomeev | W. Barletta
abstract: The authors present the status of a compact infrared free-electron laser, driven by a 20 MeV, S-band linac with a photoinjector. The 60 cm long hybrid undulator has a 1.5 cm period and a field on axis of 7.3 kG. The FEL will operate at 10.6 mu m as a high-gain amplifier, to study the high-gain FEL regime including the effects of self amplified spontaneous emission, optical guiding and saturation. The linac is the prototype of the plane-wave transformer. TDA simulation of the FEL shows a gain length of 10 cm, and a saturation power of 50 MW. (18 References).
keywords:
Download | Details | Edit | Delete
title: The operation of the BNL/ATF GUN-IV photocathode RF gun at the Advanced Photon Source
format: conference proceeding
conference: PAC 1999
year: 1999
18 authors: S. G. Biedron | G. A. Goeppner | J. W. Lewellen | S. V. Milton | A. Nassiri | G. Travish | X. J. Wang | N. D. Arnold | W. J. Berg | M. Babzien | C. L. Doose | R. J. Dortwegt | A. Grelick | J. N. Galayda | G. M. Markovich | S. J. Pasky | J. G. Power | B. X. Yang
abstract: At the Advanced Photon Source (APS) at Argonne National Laboratory (ANL), a free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) process is nearing completion. Recently, an RF photoinjector gun system was made available to the APS by Brookhaven National Laboratory/Accelerator Test Facility (BNL/ATF). It will be used to provide the high-brightness, low-emittance, and low-energy spread electron beam required by the SASE FEL theory. A Nd:Glass laser system, capable of producing a maximum of 500 mu J of UV in a 1-10 ps pulse at up to a 10-Hz repetition rate, serves as the photoinjector's drive laser. Here, the design, commissioning, and integration of this gun with the APS are discussed. (8 References).
keywords:
Download | Details | Edit | Delete
title: Beam Shaping and Compression Scheme for the UCLA Neptune Laboratory
format: conference proceeding
conference: PAC 2003
year: 2003
4 authors: R. J. England | P. Musumeci | R. Yoder | J.B. Rosenzweig
abstract: We have recently added a dispersionless translating section to the UCLA Neptune linear accelerator beamline. This new section of beamline will serve as a venue for beam shaping and compression experiments using the 14MeV electron beam produced by the UCLA Neptune PWT linac and newly installed photoinjector. An examination of the first and second-order optics indicates that when certain nonlinear effects are minimized through the use of sextupole magnets, the longitudinal dispersion is dominated by a negative R56 which, for an appropriately chirped initial beam, can be used to create a ramped beam of a few picosecond duration that would be ideal for driving large amplitude wake fields in a plasma and producing high transformer ratios. The beamline is now in operation. Preliminary data indicate that the beamline optics are well-predicted by simulation and that sextupoles can be used successfully to eliminate nonlinear horizontal dispersion. Future experiments are planned for measuring beam compression (using CTR autocorrelation) and doing longitudinal phase space tomography (using a transverse deflecting cavity).
keywords:
Download | Details | Edit | Delete
title: Initial measurements of the UCLA RF photoinjector
format: conference proceeding
conference: Conference on High Intensity Electron Sources
year: 1994
14 authors: S. Hartman | M. Hogan | S. C. Hartman | N. Barov | C. Pellegrini | S. Park | J.B. Rosenzweig | G. Travish | R. Zhang | C. Clayton | P. Davis | M. Everett | C. Joshi | G. Hairapetian
abstract: The 1.5 cell standing wave RF photoinjector has been operated for the past several months using a copper cathode. The photoinjector drive laser produces sub 2 ps pulses of UV ( lambda =256 nm) light with up to 200 mu J/pulse which generates up to 3 nC of charge, The emittance of the photoinjector was measured as a function of charge, RF launching phase, and peak accelerating field. Also, the quantum efficiency and pulse lengths of the laser beam and the electron beam were measured. (15 References).
keywords:
Download | Details | Edit | Delete
title: An Adjustable Permanent Magnet Quadrupole Final Focus System for Low Energy Experiments
format: conference proceeding
conference: PAC 2003
year: 2003
7 authors: J. Lim | P. Frigola | J.B. Rosenzweig | S. Telfer | G. Travish | W. Brown | A. Tremaine
abstract: The final focus system for the Thomson X-ray scattering experiment termed PLEIADES (Picosecond Laser-Electron InterAction for Dynamic Evaluation of Structures) at LLNL demands ultra-high field gradient quadrupoles in order to focus initially small beams to 10-20 micron spot sizes. This scheme circumvents limitations due to chromatic aberrations and space-charge effects in this relatively low energy (<100 Mev) system. The final focus scheme is based on an ultra-high gradient (300T/m) quadrupole which employs the Halbach 16-piece, permanent magnet design. Use of this optimized goemetry, NdFeB material, and a small (4 mm) bore allows the desired field gradient, and few cm focal length, to be achieved. The adjustability of the focusing system is obtained by changing the relative longitudinal positions of sub-component focusing and defocusing magnets on precision movers. We present the results of RADIA 3D design simulations, and measurement of prototype magnets. We also discuss the results of beam dynamics simulations of the PLEIADES system using both envelope and tracking codes.
keywords:
Download | Details | Edit | Delete
title: A full energy positron source for the UCLA phi factory
format: conference proceeding
conference: Workshop on Testing CPT and Studying CP Violation at a Phi Factory
year: 1991
2 authors: W. Barletta | C. Pellegrini
abstract: The authors describe a full energy injection system suitable for rapid filling of a compact phi factory with high luminosity. Several novel approaches are suggested to minimize power on the positron target and to allow single bunch injection of electrons. (4 References).
keywords:
Download | Details | Edit | Delete
title: Free electron lasers for the XUV spectral region
format: conference proceeding
conference: FEL 1984 6th
year: 1985
2 authors: J.B. Murphy | C. Pellegrini
abstract: The generation of high intensity coherent radiation in the soft X-ray region from a free electron laser will require the FEL to operate in the high gain or collective instability regime. In this mode of operation, which does not require a cavity resonator, the radiation field grows exponentially along the undulator until nonlinear effects bring on saturation. The authors discuss the conditions that the electron beam and the undulator must satisfy for the collective instability to develop. They present an example of an electron storage ring with an undulator in a bypass section which satisfies these conditions. They present estimates of the output power that one can expect from such systems. (25 References).
keywords:
Download | Details | Edit | Delete
title: First results of the Fermilab high-brightness RF photoinjector
format: conference proceeding
conference: PAC 1999
year: 1999
18 authors: J.P. Carneiro | R.A. Carrigan | Champion, M. S. | P. L. Colestock | H. T. Edwards | Fuerst, J. D. | W. H. Hartung | Koepke, K. P. | Kuchnir, M. | J. K. Santucci | Spentzouris, L. K. | Fitch, M. J. | Melissinos, A. C. | P. Michelato | C. Pagani | Sertore, D. | N. Barov | J.B. Rosenzweig
abstract: A collaboration has been formed between FNAL, UCLA, LNFN Milano, the University of Rochester, and DESY to develop the technology of an RF photoinjector, followed by a superconducting cavity, to produce high bunch charge (8 nC) with low normalized emittance ([left angle bracket]20 mm mrad) in bunch spacing trains of 800 bunches separated by mu s. The activities of bunch charge the collaboration fall into two categories: 1. the development of Injector II for the TeSLA/TTF accelerator. This photoinjector (TTF RF Gun) was tested at Fermilab in September and October 1998 and installed at DESY in November 1998. 2. the installation at the A0 Hall of Fermilab of a modified version of the TTF photoinjector, for photoinjector R&D and to study novel applications of high-brightness, pulsed electron beams. This photoinjector (A0 RF Gun) produced its first beam in March 1999. This paper presents a summary of the tests done at Fermilab on the TITF Injector II and the first results obtained on the new Fermilab photoinjector.
keywords:
Download | Details | Edit | Delete
title: Tunneling Ionization Bunch Length Monitor for the Ultrarelativistic Compressed Electron Beams
format: conference proceeding
conference: PAC 2003
year: 2003
1 author: A. Murokh
abstract: The electric field intensity of the compressed ultra-relativistic electron beams is approaching GV/m levels, which is sufficient to cause observable tunneling effect in the low band gap materials. In this article the tunneling ionization rate is estimated for the experimentally available electron beam parameters, and a proposed proof of principle experiment is outlined. Tunneling effect has exponential dependence on the electric field strength; thus being very sensitive to the electron beam peak current. This non-linear dependence opens up a possibility to construct inexpensive, single shot and non-destructive peak current diagnostics for the ultrarelativistic compressed electron beams.
keywords:
Download | Details | Edit | Delete
title: Experiment to Measure Ramped Electron Bunches at the UCLA Neptune Laboratory Using a Transverse Deflecting Cavity
format: conference proceeding
conference: AAC 2006 12th
year: 2006
5 authors: R. J. England | D. Alesini | B. O'Shea | J.B. Rosenzweig | G. Travish
abstract: A proof of principle experiment is underway at the UCLA Neptune laboratory to test the concept of generating linearly ramped relativistic electron bunches (rising in density from head to tail followed by a sharp cutoff) by using a sextupole-corrected dogleg section as a bunch compressor. Bunches with this structure have been predicted to be ideal for use as a plasma wake-field drive beam. The diagnostic being developed to measure the time profile of the beam is an X-Band (9.6 GHz) deflecting cavity. The recently completed cavity is a 9-cell standing wave structure operating in a TM110-like mode, designed to measure the temporal structure of the 2 to 10 ps, 14 MeV electron bunches generated by the Neptune S-band photoinjector and plane-wave transformer (PWT) accelerator beamline, with 50 fs resolution. We discuss the experimental plan for the ramped bunch experiment and present preliminary data related to the tuning and operation of the deflecting cavity.
keywords:
Download | Details | Edit | Delete
title: A THz radiation driven IFEL as a phaselocked prebuncher for a plasma beat-wave accelerator
format: conference proceeding
conference: International Conference on Lasers 2001
year: 2002
6 authors: P. Musumeci | S. Ya. Tochitsky | C. E. Clayton | C. Joshi | C. Pellegrini | J.B. Rosenzweig
abstract: To obtain a high quality electron beam with small energy spread in the laser driven plasma accelerator, the electrons have to be prebunched at the scale of the plasma wavelength. We study the feasibility of an experiment where an inverse free electron laser (IFEL) is used to bunch the electron beam before the injection into a plasma beatwave accelerator. It is suggested to drive the IFEL prebuncher by a THz seed radiation phase-locked to the electromagnetic beatwave through difference frequency generation process in a nonlinear crystal. Design and numerical simulations for this experiment are presented.
keywords:
Download | Details | Edit | Delete
title: The development of S-band plane wave transformer photoinjector
format: conference proceeding
conference: PAC 1999
year: 1999
11 authors: X. Ding | C. Pellegrini | J.B. Rosenzweig | S. Telfer | A. Tremaine | Vernon, W. | D. Yu | D. Newsham | Zeng, J. | Lee, T. | Chen, J.
abstract: An integrated S-band RF photoinjector based on the plane wave transformer (PWT) is being built in the Particle Beam Physics Laboratory at UCLA in collaboration with DULY Research. This novel structure integrates a photocathode directly into a PWT linac making the structure simple and compact. Due to the strong coupling between each adjacent cell, this structure is relatively easy to fabricate and operate. This photoinjector can provide high brightness beams at energies of 15 to 20 MeV, with emittance less than 1 mm-mrad at charge of 1 nC. These short-pulse beams can be used in various applications: space charge dominated beam physics studies, plasma lenses, plasma accelerators, free-electron laser microbunching techniques, and SASEFEL physics studies. It will also provide commercial opportunities in chemistry, biology and medicine. The present status of the PWT photoinjector including fabrication and cold test to characterise the structure is described. RF system and photocathode drive laser system are also discussed.
keywords:
Download | Details | Edit | Delete
title: Status of the Inverse Free Electron Laser Experiment at the Neptune Laboratory
format: conference proceeding
conference: PAC 2003
year: 2003
10 authors: P. Musumeci | C. Pellegrini | J.B. Rosenzweig | S. Tochitsky | G. Travish | R. Yoder | A. A. Varfolomeev | Tolmachev, S. | A. Varfolomeev Jr. | T. Yarovoi
abstract: We report on the status of the Inverse Free Electron Laser accelerator experiment under construction at the UCLA Neptune Laboratory. This experiment will use a 400 GW CO2 laser to accelerate through a tapered undulator an electron beam from 14.5 MeV up to 55 MeV. The scheme proposed is the diffraction dominated IFEL interaction where the Rayleigh range of the laser beam is 3.5 cm, much shorter than the interaction length (the undulator length is 50 cm). The undulator is strongly tapered in both field and period. The present status of the experiment is reported.
keywords:
Download | Details | Edit | Delete
title: Photon beam diagnostics for VISA FEL
format: conference proceeding
conference: PAC 1999
year: 1999
17 authors: A. Murokh | C. Pellegrini | J.B. Rosenzweig | Pedro Frigola | P. Musumeci | A. Tremaine | M. Babzien | Ben-Zvi, I. | A. Doyuran | E. Johnson | Skaritka, J. | X.J. Wang | Van Bibber, K. A. | J.M. Hill | G.P. Le Sage | D. C. Nguyen | M. Cornacchia
abstract: The VISA (Visible to Infrared SASE Amplifier) project is designed to be a SASE-FEL driven to saturation in the sub-micron wavelength region. Its goal is to test various aspects of the existing theory of self-amplified spontaneous emission, as well as numerical codes. Measurements include: angular and spectral distribution of the FEL light at the exit and inside of the undulator; electron beam micro-bunching using CTR; single-shot time resolved measurements of the pulse profile, using an auto-correlation technique and FROG algorithm. The diagnostics are designed to provide maximum information on the physics of the SASE-FEL process, to ensure a close comparison of the experimental results with theory and simulations. (9 References).
keywords:
Download | Details | Edit | Delete
title: Velocity Bunching Experiment at the Neptune Laboratory
format: conference proceeding
conference: PAC 2003
year: 2003
3 authors: P. Musumeci | R. B. Yoder | J.B. Rosenzweig
abstract: In this paper we describe the rectilinear compression experiment at the Neptune photoinjector at UCLA. The electron bunches have been shortened to sub-ps pulse length by chirping the beam energy spectrum in a short S-band high gradient standing wave RF cavity and then letting the electrons undergo velocity compression in the following rectilinear drift. Using a standard Martin Puplett interferometer to characterize coherent transition radiation from the beam, we measured bunch lengths as short as 0.4 ps with compression ratio in excess of 10 for an electron beam of 7 MeV energy and charge up to 300 pC.
keywords:
Download | Details | Edit | Delete
title: Bunched Beam Injection in a Plasma Accelerator
format: conference proceeding
conference: AAC 2002 10th
year: 2002
6 authors: S. Ya. Tochitsky | P. Musumeci | C. E. Clayton | C. Pellegrini | J.B. Rosenzweig | C. Joshi
abstract: An experiment on phase-locked injection of ~ 100 fs electron bunches in a plasma beat wave accelerator is presented. We consider using an IFEL microbunching technique to produce ultrashort electron bunches prebunched at the exact wavelength of the plasma wave 340 Jim (~lTHz). It is proposed to generate 100 MW of 1 THz radiation by difference frequency generation in a nonlinear crystal, mixing the same two CC>2 lines as used to drive the plasma accelerator.
keywords:
Download | Details | Edit | Delete
title: Output power control in an X-ray FEL
format: conference proceeding
conference: PAC 1999
year: 1999
3 authors: C. Pellegrini | X. Ding | J.B. Rosenzweig
abstract: Recent theoretical and experimental advances of the high gain self-amplified spontaneous emission free-electron laser (SASE-FEL), have demonstrated the feasibility of using this system as a 4/sup th/ generation light source. This source will produce diffraction-limited radiation in the 0.1 nm region of the spectrum, with peak power of tens of GW, subpicosecond pulse length, and very large brightness. The peak power density in such a system is very large, and in some experiments it might damage the optical systems or the samples, or it might be simply larger than what is needed for the particular experiment being considered. Some options to reduce the power level, for example by using a gas absorption cell to reduce the X-ray intensity, have been studied. In this paper we discuss another possibility to control the power output of an X-ray SASE-FEL by varying the charge from the electron source, and the longitudinal bunch compression during the acceleration in the linac.
keywords:
Download | Details | Edit | Delete
title: The ORION Facility
format: conference proceeding
conference: PAC 2003
year: 2003
10 authors: R.J. Noble | E.R. Colby | D. T. Palmer | R.H. Siemann | D. Walz | R. Byer | C. Joshi | W. Mori | J.B. Rosenzweig | T. Katsouleas
abstract: ORION will be a user-oriented research facility for understanding the physics and developing the technology for future high-energy particle accelerators. The ORION Facility will bring together the needed resources for performing a wide range of experiments in advanced accelerator and beam physics. The facility has as its centerpiece the Next Linear Collider Test Accelerator (NLCTA) within End Station B at the SLAC Central Research Yard. That site will be modified with the addition of a new high-brightness photoinjector, its associated drive laser and rf power system, a user laser room, a low-energy experimental hall supplied with electron beams up to approximately 60 MeV in energy, and a high-energy hall supplied with beams up to 350 MeV. Facility construction is anticipated to start in October 2003, contingent upon funding approval, and first beam is planned for 2005. The first experiment at ORION, the laser acceleration experiment E163, has been approved by SLAC. In this paper, results are presented on the revised facility layout and design which came out of the 2nd ORION Workshop in February 2003, and the beam physics design of the injector and the beamlines for the low and high-energy experimental halls.
keywords:
Download | Details | Edit | Delete
title: Short wavelength FELs using the SLAC linac
format: conference proceeding
conference: National Conference on Synchrotron Radiation Instrumentation 8th
year: 1994
6 authors: J. Cobb | P. Pianetta | J. Seeman | Vylet, V. | D. Prosnitz | Morton, P.
abstract: Recent technological developments have opened the possibility to construct a device which we call a linac coherent light source (LCLS) (C. Pellegrini et al., Nucl. Instr. and Meth. A 331 (1993) 223; H. Winick et al., Proc. IEEE 1993 Particle Accelerator Conf., Washington, DC, May 1993; C. Pellegrini, Nucl. Instr. and Meth. A 341 (1994) 326; J. Seeman, SPIE Meet. on Electron Beam Sources of High Brightness Radiation, San Diego, CA, July 1993 [1?4]); it would be a fourth-generation light source, with brightness, coherence, and peak power far exceeding other sources. Operating on the principle of the free electron laser (FEL), the LCLS would extend the range of FEL operation to much shorter wavelength than the 240 nm that has so far been reached. We report the results of studies of the use of the SLAC linac to drive an LCLS at wavelengths from about 3 to 100 nm initially and possibly even shorter wavelengths in the future. Lasing would be achieved in a single pass of a low emittance, high peak current, high-energy electron beam through a long undulator. Most present FELs use an optical cavity to build up the intensity of the light to achieve lasing action in a low-gain oscillator configuration. By eliminating the optical cavity, which is difficult to make at short wavelengths, laser action can be extended to shorter wavelengths by self-amplified-spontaneous-emission (SASE), or by harmonic generation from a longer wavelength seed laser. Short wavelength, single pass lasers have been extensively studied at several laboratories and at recent workshops (M. Cornacchia and H. Winick (eds.), SLAC Report 92/02; I. Ben-Zvi and H. Winick (eds.), BNL report 49651 [5,6]). The required low-emittance electron beam can be achieved with recently-developed rf photocathode electron guns (B.E. Carlsten, Nucl. Instr. and Meth. A 285 (1989) 313; J. Rosenzweig and L. Serafini, Proc. IEEE 1993 Particle Accelerator Conf., Washington, DC, 1993 [7,8]). The peak current is increased by about an order of magnitude by compressing the bunch to a lenght of about 0.2 ps (rms). Techniques for beam transport, acceleration, and compression without emittance dilution have been developed at SLAC as part of the linear-collider project (J. Seeman, Advances of Accelerator Physics and Technologies, ed. H. Schopper (World Scientific, Singapore, 1993 [9]). The undulator length required to saturate the laser varies from about 15 m for a 100 nm FEL to about 60 m at 3 nm. Initial experiments, at wavelengths down to about 50 nm are planned using the 25-m long Paladin undulator now located at LLNL. In a proposed future LCLS R&D facility the short wavelength light pulses are distributed to multiple end stations using grazing-incidence mirrors. About 1014 photons per pulse can be produced at a 120 Hz rate, corresponding to average brightness levels of about 1021 photons/s/mm(2)/mrad(2) within 0.1% BW and peak brightness levels of about 1031 photons/s/mm(2)/mrad(2) within 0.1% BW. Peak power levels are several hundred megawatts to several gigawatts. Electron energies required range from about 500 MeV for the 100 nm FEL to about 7 GeV for 3 nm.
keywords:
Download | Details | Edit | Delete
title: Optimal scaled photoinjector designs for FEL applications
format: conference proceeding
conference: PAC 1999
year: 1999
5 authors: J.B. Rosenzweig | S. Anderson | X. Ding | C. Pellegrini | G. Travish
abstract: Much of the research and development surrounding the effort to create X-ray FELs based on the SASE process has centered on the creation of ultra-high brightness electron beam sources. The sources for existing short wavelength FEL designs, which employ RF photoinjector technology, have all been specified to contain 1 nC of charge. We show, by scaling existing designs, that this constraint causes the maximum beam brightness to be found when the RF wavelength is shortened to X-band. If, instead of holding the charge constant, we assume a certain RF wavelength device and then scale the charge, notable improvements in the beam brightness, and thus the FEL performance, are found. Charge scaling assumes that the density and aspect ratio of the beam stays constant as the charge is changed. If we relax the requirement of a constant aspect ratio in order to maximize the beam current and brightness by shortening the beam pulse, we find that the pulse lengthening due to space charge eventually brings this effort to a stop. The results of this investigation and their impact on SASE FEL design is discussed.
keywords:
Download | Details | Edit | Delete
title: The FEL Program at the PEGASUS Injector
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: Sven Reiche | G. Andonian | P. Frigola | J.B. Rosenzweig | S. Telfer | and G. Travish
abstract: The PEGASUS photo injector at UCLA can produce a photo electrons beam with a normalized emittance of 2 mm mrad at an energy of 12-15 MeV, capable of driving a Free-Electron Laser in the mid IR regime. The FEL program, associated with the PEGASUS injector and presented here, is based on a Self-Amplifying Spontaneous Emission (SASE) FEL. The studies focus on increasing the efficiency of an FEL by novel undulator design and compensation of diffraction effects, using waveguides of millimeter size. In this presentation we also discuss the possibility of the PEGASUS FEL as a THz user facility.
keywords:
Download | Details | Edit | Delete
title: Pulse Length Control in an X-Ray FEL by Using Wakefields
format: conference proceeding
conference: PAC 2003
year: 2003
3 authors: Sven Reiche | P. Emma | C. Pellegrini
abstract: For the users of the high-brightness radiation sources of free-electron lasers it is necessary to reduce the FEL pulse length to 10 fs and below for time-resolving pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of undulator wakefields and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented.
keywords:
Download | Details | Edit | Delete
title: A Fast Method to Estimate the Gain of the Microbunch Instability in a Bunch Compressor
format: conference proceeding
conference: PAC 2003
year: 2003
2 authors: Sven Reiche | J.B. Rosenzweig
abstract: For the users of the high-brightness radiation sources of free-electron lasers it is necessary to reduce the FEL pulse length to 10 fs and below for time-resolving pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of undulator wakefields and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented.
keywords:
Download | Details | Edit | Delete
title: Space-charge oscillations in a self-modulated electron beam in multi-undulator free-electron lasers
format: conference proceeding
conference: FEL 1996 18th
year: 1997
5 authors: J.B. Rosenzweig | C. Pellegrini | L. Serafini | C. Ternieden | G. Travish
abstract: We examine here the oscillation of electron-beam density perturbations (longitudinal plasma oscillations) produced at the exit of a high-gain free-electron laser (FEL) by the action of the FEL instability. These oscillations, which are analyzed in the case of both a free-space drift and a dispersive section, can degrade the bunching of the beam in the drift between undulator sections in multi-stage FELs. The impact of these oscillations on the gain of an FEL in an undulator following such a drift, as well as the case of an optical klystron is studied. (9 References).
keywords:
Download | Details | Edit | Delete
title: Photoelectron beams from the UCLA RF gun
format: conference proceeding
conference: AAC 1992 3rd
year: 1993
12 authors: S. Park | N. Barov | S. Hartman | C. Pellegrini | J.B. Rosenzweig | P. Tran | G. Travish | R. Zhang | P. Davis | G. Hairapetian | C. Joshi | N. Luhmann
abstract: A high brightness, low emittance photocathode rf gun is starting operation at UCLA as an injector to a 20 MeV linac. This linac will initially be used to drive FELs, plasma wakefield accelerators, and to test plasma lenses. The gun is a 1 1/2 cell pi-mode standing wave structure running at 2.856 GHz, and has a copper photocathode. In the initial commissioning of the gun, photoelectron beams of up to 2.5 nC at 4.5 MeV have been produced. We report on the current status of the system, experimental data taken with 50 ps UV laser pulses, and plans for the future.
keywords:
Download | Details | Edit | Delete
title: The free electron laser and its possible developments
format: conference proceeding
conference: PAC 1979
year: 1979
1 author: C. Pellegrini
abstract: Reviews the basic characteristics, operating principles, applications and possible developments of a free electron laser in a storage ring. (18 References).
keywords:
Download | Details | Edit | Delete
title: Report of the Working Group on Near-field accelerators
format: conference proceeding
conference: AAC 1992 3rd
year: 1993
1 author: J.B. Rosenzweig
abstract: Advanced research on near-field acceleration, by the time of this meeting, has progressed into mature field of both experimental and theoretical investigation. This field has a number of subcomponents; a few of the more notable are wake-field acceleration, open structure laser acceleration, and novel RF structures. This paper will provide an overview of these subjects, and examine the most recent advances in near-field acceleration and the facilities developed for its study, as reported at the Port Jefferson workshop. (17 References).
keywords:
Download | Details | Edit | Delete
title: Free electron laser experiment at the NSLS 700 MeV electron storage ring
format: conference proceeding
conference: PAC 1981
year: 1981
11 authors: J. P. Blewett | L. Blumberg | A. J. Campillo | R. P. DiNardo | H. C. Hsieh | S. Krinsky | A. Luccio | C. Pellegrini | J. Schuchman | P. Z. Takacs | A. van Steenbergen
abstract: A free electron laser experiment is described, to be performed with the 700 MeV electron storage ring of the National Synchrotron Light Source. The experiment is designed to study the parameters of the fel in an electron storage ring and the performance of this laser as a source of short wavelength radiation in the VUV region of the spectrum. The initial experiment will be carried out at a wave length of approximately 3000 AA, utilizing a permanent magnet undulator. For an average electron current of 1 A distributed in three beam bunches, the small signal gain per pass (relative enhancement of the radiation intensity per electron bunch pass through the undulator) is calculated to be approximately 10%. (11 References).
keywords:
Download | Details | Edit | Delete
title: Asymmetric emittance RF photocathode source for linear collider applications
format: conference proceeding
conference: AAC 1992 3rd
year: 1993
2 authors: J.B. Rosenzweig | Smolin, J. A.
abstract: Laser driven RF photocathodes represent a recent advance in high-brightness electron beam sources. The authors investigate here a variation on these devices, that obtained by using a ribbon laser pulse to illuminate the cathode, yielding a flat beam (sigma_x >> sigma_y) which has asymmetric emittances at the cathode proportional to the beam size each transverse dimension. The flat-beam geometry mitigates space charge forces which lead to intensity dependent transverse and longitudinal emittance growth, thus limiting the beam brightness. The fundamental limit on achievable emittance and brightness is set by the transverse momentum distribution and peak current density of the photo-electrons (photon energy and cathode material dependent effects) and appears to allow, taking into account space charge and RF effects, normalized emittances epsilon_x <1x10(-4) m-rad and epsilon_y < 10(-6) m-rad, with Q = 5 nC and sigma_z = 1 mm. These source emittances are adequate for superconducting linear collider applications, and could preclude the use of a damping ring for the electrons in these schemes.
keywords:
Download | Details | Edit | Delete
title: The plane wave transformer linac development at UCLA
format: conference proceeding
conference: PAC 1993
year: 1993
3 authors: R. Zhang | S. Hartman | C. Pellegrini
abstract: A plane wave transformer linac (PWT), offering advantages of high efficiency, compactness, fabrication simplicity and cost, is being developed at UCLA. The PWT prototype at UCLA is an 8-cell, pi -mode, S-band standing-wave linac. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 3-D code MAFIA. A microwave test-stand with a network analyzer has also been set up to test these properties. In this paper. We present the important physical features, such as mode structures, dispersion curves, wake field, from the computation and/or the experiment. The measurements show good agreement with the numerical computation. (7 References).
keywords:
Download | Details | Edit | Delete
title: Longitudinal instabilities in circular accelerator and storage rings
format: conference proceeding
conference: PAC 1981
year: 1981
1 author: C. Pellegrini
abstract: Coherent instabilities of particle beams in circular accelerators and storage rings have been the subject of many theoretical and experimental works. The coherent instabilities discussed are produced by the electromagnetic interaction of the charged particle beam with the walls of the vacuum chamber in which the beam is moving. The author reviews the general problem of the longitudinal stability of bunched beams. Although there is no general solution it is possible to identify regions in the frequency-risetime space where one can obtain approximate solutions. An expression for the collective oscillation frequency is presented and expressions for the effective coupling impedance are given for the high or low frequency and slow and fast blow-up regimes. (14 References).
keywords:
Download | Details | Edit | Delete
title: Strong sextupole focusing for planar undulators
format: conference proceeding
conference: AAC 1992 3rd
year: 1993
2 authors: G. Travish | J.B. Rosenzweig
abstract: The range of parameters in which the free electron laser (FEL) is used has greatly expanded in recent years. The present trend towards short wavelength operations with long undulators places tight requirements on the electron beam quality. In particular, the need to maintain a well focused beam is critical to successful operation of such an FEL. This paper examines the use of alternating gradient (AG) sextupole focusing in planar undulators. After a brief review of various undulator focusing schemes, the equations of motion for an electron in an undulator field with a strong sextupole component are examined. It is shown that the mean electron longitudinal velocity can be kept constant through each focusing and defocusing section. Thus, the betatron velocity modulation associated with transverse focusing can be limited. Analytic as well as smooth approximation solutions are provided for AG sextupole focusing. Examples using the proposed SLAC 4 nm FEL as well as the UCLA 10.6 um FEL parameters are also discussed.
keywords:
Download | Details | Edit | Delete
title: Plasma Density Transition Trapping as a Possible High-Brightness Electron Beam Source
format: conference proceeding
conference: ICFA Workshop on Physics and Applications of High Brightness Electron Beams
year: 2003
3 authors: M.C. Thompson | J.B. Rosenzweig | H. Suk
abstract: Plasma density transition trapping is a recently purposed self-injection scheme for plasma wake-field accelerators. This technique uses a sharp downward plasma density transition to trap and accelerate background plasma electron in a plasma wake-field. This paper examines the quality of electron beams captured using this scheme in terms of emittance, energy spread, and brightness. Two-dimensional Particle-In-Cell (PIC) simulations show that these parameters can be optimized by manipulating the plasma density profile. We also develop, and support with simu- lations, a set of scaling laws that predict how the brightness of transition trapping beams scales with the plasma density of the system. These scaling laws indicate that transition trapping can produce beams with brightness ≥ 5 x 10 14 Amp / (m- rad) 2 . A proof-of-principle transition trapping experiment is planned for the UCLA Neptune Laboratory in the near future. The proposed experiment and its status are described in detail.
keywords:
Download | Details | Edit | Delete
title: Design and Construction of High Brightness RF Photoinjectors for TESLA
format: conference proceeding
conference: PAC 1995
year: 1995
6 authors: E. Colby | Bharadwaj, V. | Ostiguy, J. F. | Nicol, T. | M. Conde | J.B. Rosenzweig
abstract: The design, construction and testing of a high brightness high bunch charge RF photoinjectormatching the requirements of the TESLA Test Facility is discussed. Engineering design work, the results of cold test measurements, and the planned experimental program are presented. Conceptual design work leading to an advanced high-brightness asymmetric emittance RF photoinjector for application to TESLA500 is also briefly discussed.
keywords:
Download | Details | Edit | Delete
title: Storage ring design for a short wavelength FEL
format: conference proceeding
conference: PAC 1985
year: 1985
12 authors: K. J. Kim | J. Bisognano | S. Chattopadhyay | M. Cornacchia | A. Garren | K. Halbach | A. Jackson | H. Lancaster | J. Peterson | M. Zisman | C. Pellegrini | G. Vignola
abstract: A high gain free electron laser (FEL) operating in a special bypass of a storage ring can provide tens of megawatts of coherent power at wavelengths shorter than 1000 AA. The requirements on beam qualities are demanding, a few hundred amperes of peak current in an emittance of about 10/sup -8/ m-rad with a relative energy spread of approximately 10/sup -3/. Designing an electron storage ring with the required characteristics involves a comprehensive analysis of the restrictions from, and relationships between, the FEL physics, the multiparticle beam phenomena, and the ring lattice structure. A summary of such a study is reported and some design examples are given. (12 References).
keywords:
Download | Details | Edit | Delete
title: Design of High Brightness Symmetric and Asymmetric Emittance RF Photoinjectors for TESLA
format: conference proceeding
conference: AAC 1994 6th
year: 1995
3 authors: E. Colby | Ostiguy, J. F. | J.B. Rosenzweig
abstract: Development work leading to emittance-compensated symmetric emittance and asymmetric emittance RF photoinjectors is discussed. A mature design for a symmetric emittance photoinjector is described, and current work leading to an asymmetric design is detailed. An experimental program to characterize both injectors and to explore the physical mechanism of emittance compensation using the facilities of the Argonne Wakefield Accelerator is outlined. (15 References).
keywords:
Download | Details | Edit | Delete
title: A Resonant, THz Slab-Symmetric Dielectric-Based Accelerator
format: conference proceeding
conference: ICFA Workshop on Physics and Applications of High Brightness Electron Beams
year: 2003
2 authors: R. B. Yoder | J.B. Rosenzweig
abstract: Slab-symmetric dielectric-loaded structures, consisting of a vacuum gap between dielectric-lined conducting walls, have become a subject of interest for highgradient acceleration of high-charge beams due to their simplicity, relatively low power density, and advantageous beam dynamics. Such a structure can be resonantly excited by an external power source and is known to strongly suppress transverse wakefields. Motivated by the prospect of a high-power FIR radiation source, currently under construction at UCLA, we investigate a high-gradient slabsymmetric accelerator powered by up to 100 MW of laser power at 340 ?m, with a predicted gradient near 100 MeV/m. Theory and simulation studies of the structure fields and wakes are presented, with an outline of a future experiment.
keywords:
Download | Details | Edit | Delete
title: Measurements of plasma wake-fields in the blow-out regime
format: conference proceeding
conference: PAC 1995
year: 1995
9 authors: N. Barov | M. Conde | J.B. Rosenzweig | Schoessow, P. | Cox, G. | W. Gai | Konecny, R. | J. Power | J. Simpson
abstract: Initial results from nonlinear plasma wake-field experiments at the Argonne Wakefield Accelerator (AWA) test facility are reported. This nonlinear "blow-out" regime is characterized by the complete ejection of the plasma electrons from the beam channel. The wake-fields in this case are of notably high quality for acceleration of electrons, as the acceleration is independent of transverse position, and the focusing is linear and independent of longitudinal position within the electron depleted region, allowing self-consistent guiding of the majority of the driving electron beam. Initial measurements of the energy gain in a witness beam indicate a positive shift in its energy distribution of at least 0.5 MeV. (9 References).
keywords:
Download | Details | Edit | Delete
title: A study for a 6 GeV undulator based synchrotron radiation source
format: conference proceeding
conference: PAC 1985
year: 1985
9 authors: G. Vignola | M. Barton | R. Blumberg | J. Galayda | S. Krinsky | A. Luccio | C. Pellegrini | A. van Steenbergen | J. Wang
abstract: A partial study for a 6 GeV undulator based synchrotron radiation source for production of high brightness undulator radiation, in the angstrom region, is presented. The basic lattice adopted for the storage ring is a hybrid FODO Chasman-Green lattice, making use of gradient in the dipoles. The e beam current limits and the injection parameters are discussed. (8 References).
keywords:
Download | Details | Edit | Delete
title: Design and operation of a novel, compact 20 MeV linac at UCLA
format: conference proceeding
conference: Intense Microwave and Particle Beams II
year: 1992
9 authors: P.G. Davis | G. Hairapetian | C. Joshi | N. C. Luhmann | S. C. Hartman | S. Park | C. Pellegrini | J.B. Rosenzweig | J. A. Smolin
abstract: A novel, compact S-band linac has been designed and is currently under construction at UCLA. It is expected to deliver high brightness, 200 A, 20 MeV electron pulses, less than 4 ps in duration from a device that is about 1 meter long. It comprises: (a) a laser photocathode driven gun that produces 4.5 MeV electron bunches from a 1/sup 1///sub 2/ cell cavity operating in the pi -mode and (b) an accelerating structure known as a plane wave transformer (PWT) designed by Swenson (1988). The design considerations of the machine and initial operating experience of the gun are discussed. The linac will be used for free electron laser, advanced accelerator research and beam-plasma experiments. (8 References).
keywords:
Download | Details | Edit | Delete
title: The UCLA compact high brightness electron accelerator
format: conference proceeding
conference: PAC 1995
year: 1995
10 authors: P. Davis | G. Hairapetian | M. Hogan | C. Joshi | M. Lampel | S. Park | C. Pellegrini | J.B. Rosenzweig | G. Travish | R. Zhang
abstract: We report the characteristics and performance of the UCLA S-band compact electron accelerator, consisting of a high brightness, 8 cm long, photo-injector with a copper cathode, followed by a 42 cm long plane wave transformer accelerating structure, delivering a beam energy of 10 MeV. The photo-electrons are produced by a 266 nm laser pulse of less than 4 ps in duration. Over time the laser induced electron emission decreases and the emission from the cathode surface becomes structured. Measurements of the quantum efficiency for Cu before and after this degradation are presented along with images of the non uniform electron emission. (8 References).
keywords:
Download | Details | Edit | Delete
title: Transverse Focussing Using Plasma Wake Fields
format: conference proceeding
conference: PAC 1987
year: 1987
4 authors: D.B. Cline | Cole, B. | J.B. Rosenzweig | Norem, J.
abstract: Dense particle beams travelling in plasmas can produce very high electric and magnetic fields, and these fields, described by Chen and others can be used to accelerate and focus particles. The effects on trailing beams and self focussing can be strong and nonlinear. This paper discusses two aspects of self pinching beams: 1) the production of beams which do not self pinch, and 2) a short focal length plasma lens which uses self pinching to reduce beam sizes at the interaction point of a linear collider. As an example, we consider a final focus system for the Stanford Linear Collider, considering plasma production, vacuum system and backgrounds, and show how the luminosity could be increased using this system. We also discuss experimental tests of the plasma lens concept.
keywords:
Download | Details | Edit | Delete
title: Summary of Exotic Collider Concepts Group
format: conference proceeding
conference: AAC 1994 6th
year: 1995
1 author: C. Pellegrini
abstract: We present a summary of the discussions in the Exotic Collider Concepts Group. Most of the discussions were centered around the status and open problems for muon-muon and gamma-gamma colliders. In addition the group discussed some general problems and new results of accelerator physics.
keywords:
Download | Details | Edit | Delete
title: UV free electron lasers for synchrotron radiation sources
format: conference proceeding
conference: Japanese/USA Seminar on Synchrotron Radiation Facilities
year: 1980
1 author: C. Pellegrini
abstract: The author discusses the possibility of operating a free electron laser in an electron storage ring similar to those being designed or built as synchrotron radiation sources. The laser output power is proportional to the total power radiated as synchrotron radiation in the ring. The electron beam properties make the storage ring particularly suitable for operating a laser in the UV region. Small signal gain per pass larger than one at wavelengths near 600 AA can be obtained in a 500 MeV storage ring. (16 References).
keywords:
Download | Details | Edit | Delete
title: Status of the UCLA high-gain infrared free electron laser
format: conference proceeding
conference: PAC 1995
year: 1995
5 authors: M. Hogan | C. Pellegrini | J.B. Rosenzweig | G. Travish | A. A. Varfolomeev
abstract: A compact, infrared (10-20 mu m), high-gain FEL is being commissioned at the Particle Beam Physics Laboratory (PBPL) at UCLA. A 60 cm long undulator with a period of 1.5 cm and an undulator parameter K-l has been built to be used in conjunction with the PBPL beam. Experiments will focus on EEL physics pertinent to proposed short wavelength devices. Of particular interest is exploration of startup from noise, self amplified spontaneous emission (SASE), beam parameter effects on gain, and output power fluctuations. Beam micro-bunching due to the FEL action will also be measured using coherent transition radiation. Here we present an overview of the relevant diagnostics, FEL simulation results and proposed experiments. (13 References).
keywords:
Download | Details | Edit | Delete
title: Thermal Limits on Wave Amplitude in the Plasma Wake-Field Accelerator
format: conference proceeding
conference: PAC 1987
year: 1987
1 author: J.B. Rosenzweig
abstract: We discuss the nonlinear regime of the Plasma Wakefield Accelerator and its potential advantages over linear operation, and describe the general behavior of the plasma electron phase space in large amplitude plasma waves. We develop a Hamiltonian formalism for calculating the trapping of thermal electrons from the background plasma, and derive approximate limits on plasma wave amplitude due to loading by trapped electrons and other thermal effects.
keywords:
Download | Details | Edit | Delete
title: Charge and Wavelength Scaling of RF Photoinjector Designs
format: conference proceeding
conference: AAC 1994 6th
year: 1995
2 authors: J.B. Rosenzweig | E. Colby
abstract: The optimum design of an emittance compensated rf photoinjector is very complicated and time-consuming, relying heavily on multi-particle simulations without good analytical models as a guide. Emittance compensated designs which have been developed, however, can be used to generate other designs with no additional effort if the original design is scaled correctly. This paper examines the scaling of rf photoinjector design with respect to charge and wavelength, and presents emittance and brightness scaling laws for these variables. Parametric simulation studies are presented to illustrate these scaling laws. Deviations from scaling and practical considerations are also discussed.
keywords:
Download | Details | Edit | Delete
title: Phenomenological analysis of current limits in storage rings
format: conference proceeding
conference: Japanese/USA Seminar on Synchrotron Radiation Facilities
year: 1980
2 authors: C. Pellegrini | M. Sands
abstract: The authors report the limitations on the current which can be stored in a storage ring. A simple model is used for the impedance of the beam environment. They assume that feedback systems are used to their full capacity to provide beam stability and that in the frequency range where feedback can no longer be used Landau damping will determine how much current can be stored in the ring. Estimates are made for the proton storage rings and for the electron storage rings of interest as synchrotron radiation sources and for colliding beam systems for high energy physics. (13 References).
keywords:
Download | Details | Edit | Delete
title: Progress on Plasma Lens Experiments at the Final Focus Test Beam
format: conference proceeding
conference: PAC 1995
year: 1995
34 authors: P. Kwok | Chen, P. | D. B. Cline | W. Barletta | Berridge, S. | Bugg, W. | Bula, C. | S. Chattopadhyay | Craddock, W. | Hsu, I. | R. Iverson | T. Katsouleas | Lai, P. | Leemans, W. | Liou, R. | McDonald, K. T. | D. Meyerhofer | Nakajima, K. | Nakanishi, H. | Ng, C. K. | Nishida, Y. | Norem, J. | A. Ogata | J.B. Rosenzweig | Ross, M. | Sessler, A. M. | Shintake, T. | Spencer, J. | Su, J. J. | Weidemann, A. W. | Westenskow, G. | D. Whittum | Williams, R. | J. Wurtele
abstract: The proposal to perform a series of plasma lens experiments at the Final Focus Test Beam at SLAC has been described earlier. We report on our progress towards validation of concepts involved in the experiments, including the laser ionized plasma production test, development of the supersonic gas jet as the plasma source, and study on focused beam size measurement techniques. Most importantly, the effects of background events due to plasma lenses in future linear collider detectors, such as that in the NLC, are studied in details and are shown to be within detector tolerances.
keywords:
Download | Details | Edit | Delete
title: A dielectric-loaded resonant laser accelerator
format: conference proceeding
conference: AAC 1994 6th
year: 1995
3 authors: J.B. Rosenzweig | A. Murokh | C. Pellegrini
abstract: A laser-pumped accelerator utilizing a resonant, periodic, dielectric-loaded structure is proposed. The electromagnetic fields due to a side-injected laser beam impinging on this structure are described in a two-dimensional standing-wave approximation, and analyzed in terms of their suitability for accelerating electrons to ultra-relativistic energies. The longitudinal dynamics of injected electrons in the capture phase of the motion are discussed, as are the first and second order transverse focusing effects inherent in this type of structure. Similarities and differences between this scheme, and conventional as well as advanced accelerators, and practical issues relevant to experimental realization of laser acceleration are examined. (20 References).
keywords:
Download | Details | Edit | Delete
title: Applications of short bunches
format: conference proceeding
conference: Micro Bunches Workshop
year: 1996
1 author: C. Pellegrini
abstract: We discuss the applications of short, high brightness, high intensity electron bunches to colliders, generators of X-ray radiation like FELs and Compton backscattering, and high frequency linear accelerators like laser or plasma wakefield accelerators. (8 References).
keywords:
Download | Details | Edit | Delete
title: The UW/ANL plasma wake-field acceleration experiment
format: conference proceeding
conference: PAC 1987
year: 1987
5 authors: J.B. Rosenzweig | D.B. Cline | Cole, B. | Detra, J. | Sealy, P.
abstract: An experiment designed to test the physics of the plasma wake-field accelerator (PWFA) using the ANL (Argonne National Laboratory) Advanced Accelerator Test Facility is described. A discussion of theoretical predictions is followed by a status report on the experimental study of the plasma source and diagnostics, the beam diagnostics, and the computer control and data acquisition. The experimental goals are briefly examined. (8 References).
keywords:
Download | Details | Edit | Delete
title: An injector-prebuncher for a plasma electron accelerator
format: conference proceeding
conference: PAC 1995
year: 1995
5 authors: M. Lampel | C. Pellegrini | R. Zhang | C. Joshi | W. M. Fawley
abstract: Optimum operation of a plasma beat-wave or wakefield accelerator requires an injected beam consisting of a train of electron bunches separated by the plasma wavelength, with each bunch in the train having a length much shorter than the plasma wavelength, and the capability of controlling the relative phase of the electron bunches and plasma wave. The typical plasma wavelength is about 0.1 mm, requiring a bunch length of about 10 to 20 mu m, which is difficult to achieve with conventional RF based injectors. In this paper we describe an electron accelerator-buncher system based on a photoinjector and an FEL, which can satisfy the plasma accelerator requirements. (4 References).
keywords:
Download | Details | Edit | Delete
title: Report of the Working Group on Electron Sources
format: conference proceeding
conference: AAC 1994 6th
year: 1995
1 author: J.B. Rosenzweig
abstract: We report in this paper on the activities of the working group on electron sources at the Advanced Accelerator Workshop held in Lake Geneva, Wisconsin in June 1994. The discussion, while dominated by the subject of rf photoinjectors, included explorations of many novel areas in the state-of-the-art in electron source research and development. The major points raised at the workshop are examined, and a guide to the detailed reports of the members of the working group is provided.
keywords:
Download | Details | Edit | Delete
title: Electron micro-bunch generation from RF photoinjectors
format: conference proceeding
conference: Micro Bunches Workshop
year: 1996
3 authors: L. Serafini | R. Zhang | C. Pellegrini
abstract: In this paper we discuss how the injector specifications of a 2nd-generation plasma beat wave accelerator (PBWA) experiment can be achieved by a photo-injector. Typical required bunch lengths (FWHM) are 50 microns with 15 pC bunch charge. We analyze the possibility of generating such short electron bunches directly from a photoinjector by illuminating a photocathode in an RF electron gun with a phase-locked 160-fs laser pulse. In particular, we address all de-bunching effects taking place during acceleration and transport through the photo-injector. We provide a set of analytical scaling laws, as well as a comparison with detailed simulations of the beam dynamics. The possible performances of the present SATURNUS linac setup are presented, as well as the anticipated capabilities of a multi-cell RF gun structure based on the PWT linac presently in operation at UCLA. (17 References).
keywords:
Download | Details | Edit | Delete
title: Progress in the Design of a DC FEL Power Source Using a Pelletron Driver
format: conference proceeding
conference: PAC 1987
year: 1987
7 authors: Larson, D. J. | D.B. Cline | S. Anderson | J.B. Rosenzweig | Sundquist, M. L. | Adney, J. R. | Dehais, S. J.
abstract: We discuss progress in the design of a DC Free Electron Laser power source using a Pelletron electrostatic accelerator as a driver. Such a power source should deliver up to 200 kW DC power in wavelengths ranging from a few microns to a few centimeters. The advantages of this system for use as a power source for future acceleration techniques are its efficiency, tunability and high average power. In order to achieve DC operation of the system extremely high electron recovery efficiencies are required. It is also likely that FEL operation will result in a large spread of electron energies. These design constraints require the development of a highly efficient electron beam collector as well as beam optics capable of recirculating beams with a large energy spread. We present collector and beamline designs and include electron optics studies for the full range of operating conditions.
keywords:
Download | Details | Edit | Delete
title: Charge and Wavelength Scaling of RF Photoinjectors: A Design Tool
format: conference proceeding
conference: PAC 1995
year: 1995
2 authors: J.B. Rosenzweig | E. Colby
abstract: The optimum design of an emittance compensated rf photoinjector is very complicated and time-consuming, relying heavily on multi-particle simulations without good analytical models as a guide. Emittance compensated designs which have been developed, however, can be used to generate other designs with no additional effort if the original design is scaled correctly. This paper examines the scaling of rf photoinjector design with respect to charge and wavelength, and presents emittance and brightness scaling laws for these variables. Parametric simulation studies are presented to illustrate these scaling laws. A practical design for the TESLA FEL rf photo-injector is developed using these scaling techiniques.
keywords:
Download | Details | Edit | Delete
title: Initial commissioning results of the Next Generation Photoinjector
format: conference proceeding
conference: AAC 1997 7th
year: 1997
11 authors: D. T. Palmer | X.J. Wang | R. H. Miller | M. Babzien | Ben-Zvi, I. | C. Pellegrini | Sheehan, J. | Skaritka, J. | H. Winick | M. Woodle | V. Yakimenko
abstract: The BNL/SLAC/UCLA symmetrized 1.6 Cell S-band emittance-compensated photoinjector has been installed at the Brookhaven Accelerator Test Facility (ATF). The commissioning results and performance of the photocathode injector are presented. This emittance-compensated photoinjector consists of the symmetrized BNL/SLAC/UCLA 1.6 cell S-band photocathode radio-frequency (RF) gun and a single solenoidal magnet for transverse emittance compensation. The highest acceleration field achieved on the cathode is 150 MV/m, and the normal operating field is 130 MV/m. The quantum efficiency of the copper cathode was measured to be 4.5*10/sup -5/. The transverse emittance and bunch length of the photoelectron beam were measured. The optimized RMS normalized emittance for a charge of 300 pC is 0.7 pi mm-mrad. The bunch length dependency of photoelectron beam on the RF gun phase and acceleration fields were experimentally investigated. (11 References).
keywords:
Download | Details | Edit | Delete
title: High-energy inverse free-electron laser accelerator
format: conference proceeding
conference: Summer School on High Energy Particle Accelerators
year: 1985
3 authors: E. D. Courant | C. Pellegrini | W. Zakowicz
abstract: The authors study the inverse free electron laser (IFEL) accelerator and show that it can accelerate electrons to the few hundred GeV region with average acceleration rates of the order of 200 MeV/m. Several possible accelerating structures are analysed, and the effect of synchrotron radiation losses is studied. The longitudinal phase stability of accelerated particles is also analysed. A Hamiltonian description, which takes into account the dissipative features of the IFEL accelerator, is introduced to study perturbations from the resonant acceleration. Adiabatic invariants are obtained and used to estimate the change of the electron phase space density during acceleration process. (22 References).
keywords:
Download | Details | Edit | Delete
title: Analytical model for emittance compensation in RF photo-injectors
format: conference proceeding
conference: PAC 1995
year: 1995
2 authors: L. Serafini | J.B. Rosenzweig
abstract: In this paper we present a new model to represent analytically the transverse beam dynamics in RF photo-injectors. It consists basically of an enhanced Kim's model, with incorporation of RF ponderomotive focusing effects, external magnetic focusing and a perturbative treatment of space charge along the beam envelope. Applying the resulting formulas it is possible to predict with high accuracy the transverse beam envelope behaviour in a multi-cell RF gun, as well as the operating conditions to achieve space charge emittance compensation according to Carlsten's scheme. The agreement with sophisticated numerical simulations is really quite satisfactory, as well as the match with experimental measurements of the predicted operating range for emittance compensation. (7 References).
keywords:
Download | Details | Edit | Delete
title: The inverse free-electron laser accelerator
format: conference proceeding
conference: Summer School on High Energy Particle Accelerators
year: 1983
2 authors: C. Pellegrini | I. E. Campisi
abstract: The authors discuss far field accelerators and in particular the 'inverse free-electron laser' which operates on the same principles as the free-electron laser. (14 References).
keywords:
Download | Details | Edit | Delete
title: Measurements of the octupole-induced amplitude-dependent frequency shift in SPEAR
format: conference proceeding
conference: PAC 1995
year: 1995
5 authors: Tran, P. | C. Pellegrini | Yang, J. | M. Cornacchia | Corbett, J.
abstract: Four octupoles are used in SPEAR to provide the frequency spread for Landau damping of coupled-bunch motions at high current. With the planned implementation of a new low-emittance lattice, the effectiveness of the octupoles needs to be quantified. The recent development of a multi-dimensional turn-by-turn phase-space monitor and the availability of an accurate frequency analysis technique have made measurement of the octupole-induced amplitude-dependent frequency shift in the new SPEAR lattice possible. This paper presents the data collection and analysis procedures, and compares experimental results to model-based simulations. (5 References).
keywords:
Download | Details | Edit | Delete
title: A Linear Collider Based on Nonlinear Plasma Wake-field Acceleration
format: conference proceeding
conference: Summer Study on New Directions for High Energy Physics
year: 1997
3 authors: J.B. Rosenzweig | N. Barov | E. Colby
abstract: A proposal for a linear collider based on an advanced accelerator scheme, plasma wake-field acceleration in the extremely nonlinear regime is discussed. In this regime, many of the drawbacks associated with preservation of beam quality during acceleration in plasma are mitigated. Experimental progress towards high-gradient acceleration in this scheme is reviewed. We then examine a linear collider based on staging of many modules of plasma wake-field accelerator, all driven by a high average current, pulse compressed, rf photoinjector-fed linac. Issues of beam loading, efficiency, optimized stage length, and power efficiency are discussed. A proof-of-principle experimental test of the staging concept and the Fermilab Test Facility is discussed.
keywords:
Download | Details | Edit | Delete
title: Results of blowout regime propagation experiments of an electron beam in a plasma
format: conference proceeding
conference: PAC 1997
year: 1998
4 authors: N. Barov | M. Conde | W. Gai | J.B. Rosenzweig
abstract: When a tightly focused electron beam propagates in an underdense plasma (beam density greater than the plasma electron density, n b > n 0 ), the plasma electrons are expelled radially by the space-charge of the beam, forming an ion channel which in turn provides a uniform, linear focusing force on the beam. When the beam is short ( σ z < 2 k p − 1 ), making it suitable as a driver for plasma wake-field acceleration (PWFA)[3], requirements on the beam properties (current, eminence and energy) to achieve ion channel self-focusing become more difficult to satisfy[10]. If the beam is initially β - matched to the focusing gradient, that is, the β -function is initially equal to βγπ eq e rn = /2 0 , where σ r and ε , are the rms transverse beam radius and emittance, the transverse distribution in the body of the beam is nearly stationary, while that near the head expands radially. The loss in beam density near the head associated with this expansion further retards the plasma electron response and causes the pinch point (where sufficient focusing gradient develops) to move backwards in the beam frame. The fast relaxation distance for these beam head dynamics is roughly 4 β eq , or 5 cm for our experimental conditions, which is less than half of the plasma length, L p = 12 cm. The present experiments were motivated by the proposed use of the underdense regime as the basis for a PWFA[8] (the blowout regime) which is very attractive in terms of drive and accelerating beam guiding, in that when a plasma-electron free ion column is formed, the focusing force in this region is linear and the acceleration gradient is independent of radius.
keywords:
Download | Details | Edit | Delete
title: Two beam behaviour of the 1.5 GeV electron positron storage ring ADONE
format: conference proceeding
conference: HEACC 1971 8th
year: 1971
13 authors: F. Amman | M. Bassetti | A. Cattoni | V. Chimenti | D. Fabiani | M. Matera | C. Pellegrini | M. Placidi | M. Preger | A. Renieri | S. Tazzari | F. Tazzioli | G. Vignola
abstract:
keywords:
Download | Details | Edit | Delete
title: Limitations on Measuring a Transverse Profile of Ultradense Electron Beams with Scintillators
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: A. Murokh | J.B. Rosenzweig | Ben-Zvi, I. | X. Wang | V. Yakimenko
abstract: As the high-brightness electron beams become denser and reach sub-100 um sizes, a resolution of the transverse profile diagnostics become an important issue. The applicability of the traditional scintillators as the diagnostics for most generic transverse properties of small dense beams is questionable. Recently, a YAG:Ce single crystal was used successfully, but studies indicated the presence of saturation effects. At BNL-ATF (Accelerator Test Facility) we have generated ultra-small beams, and continued an experimental work to further illuminate the nature of YAG:Ce saturation. We have also evaluated alternative diagnostics, such as LuAG:Ce. Imaging properties of various diagnostics were studied, including measurements of emission spectra.
keywords:
Download | Details | Edit | Delete
title: On the IFEL experiment at the UCLA Neptune Lab
format: conference proceeding
conference: PAC 2001
year: 2001
6 authors: P. Musumeci | C. Pellegrini | J.B. Rosenzweig | A. A. Varfolomeev | Tolmachev, S. | T. Yarovoi
abstract: We present an inverse free electron laser accelerator proposed for construction at the UCLA Neptune Lab. This experiment will use a 1TW CO/sub 2/ laser to accelerate through two strongly tapered undulators an electron beam from 16 MeV up to 55 MeV. The scheme proposed is the diffraction dominated IFEL interaction. The Raleigh range of the laser beam is about 2 cm, much shorter than the interaction length (the undulator length is 50 cm). In this regime adiabatic capture is possible in the first part of the undulator. In the focus region, we propose a solution to the problem of the dephasing between electrons and photons due to the Guoy phase shift. Ponderomotive effects and implications for tolerances are also studied. (13 References).
keywords:
Download | Details | Edit | Delete
title: Development of an X-Band PWT Photoinjector
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: D. Newsham | Luo, Y. | Zeng, J. | D. Yu | J.B. Rosenzweig
abstract: Development of an X-band Plane-Wave-Transformer (PWT), integrated photoinjector continues. Modifications of the end-cell design in this two-section device allow for simultaneous frequency and phase tuning of the accelerating field, thus preventing deceleration at the drift region that separates the two sections. The Los Alamos version of PARMELA is used to determine the expected performance parameters from the final design.
keywords:
Download | Details | Edit | Delete
title: ORION: An Advanced Accelerator Facility at SLAC
format: conference proceeding
conference: PAC 2001
year: 2001
13 authors: D. T. Palmer | E. Colby | M. Hogan | R. Noble | R. H. Siemann | Spencer, J. | D. Walz | C. Joshi | W. Mori | J.B. Rosenzweig | T. Katsouleas | P. Muggli | R. Byer
abstract: Extending the center-of-mass energy frontier for high-energy physics depends on the research and development that is conducted now in the area of advanced accelerator physics and technology. In this article, we present the design and beam dynamics simulations for the emittance-compensated, RF photoinjector of the ORION Facility. (4 References).
keywords:
Download | Details | Edit | Delete
title: Intra-undulator measurements at VISA FEL
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
11 authors: A. Murokh | P. Frigola | C. Pellegrini | J.B. Rosenzweig | A. Tremaine | E. Johnson | X.J. Wang | V. Yakimenko | L. Klaisner | H-D. Nuhn | A. Toor
abstract: We describe a diagnostics system developed, to measure exponential gain properties and the electron beam dynamics inside the strong focusing 4-m long undulator for the VISA (Visible to Infrared SASE Amplifier) FEL. The technical challenges included working inside the small undulator gap, optimising the electron beam diagnostics in the high background environment of the spontaneous undulator radiation, multiplexing and transporting the photon beam. Initial results are discussed.
keywords:
Download | Details | Edit | Delete
title: The free-electron laser collective instability and the development of X-ray FELs
format: conference proceeding
conference: PAC 2001
year: 2001
1 author: C. Pellegrini
abstract: We discuss the physics of collective instabilities in particle beams, and consider one particular case: the free-electron laser (FEL) collective instability. We present a review of the main characteristics of this instability, and its application to the development of Self Amplified Spontaneous Emission (SASE) FELs from the infrared to the X-ray region. (17 References).
keywords:
Download | Details | Edit | Delete
title: The PEGASUS free electron laser laboratory
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
4 authors: S. Telfer | Sven Reiche | J.B. Rosenzweig | P. Frigola
abstract: The PEGASUS (Photoelectron Generated Amplified Spontaneous Radiation Source) free electron laser laboratory is currently being commissioned at UCLA.
keywords:
Download | Details | Edit | Delete
title: Automated Design for Standing Wave Electron Photoguns: TOPGUN RF Design
format: conference proceeding
conference: IPAC 2016
year: 2016
3 authors: A. Cahill | M. Dal Forno | V.A. Dolgashev
abstract: Systematic design of RF photoguns involves multiple RF simulations in conjunction with beam dynamic simulations. RF simulations include tuning gun frequency, matching the gun to the feeding RF circuit, balancing the on axis electric fields between gun cells, minimizing surface electric and magnetic fields and power consumption, and optimizing separation of resonant mode frequencies. We created a tool that allows this multiple parameter optimization to be done automatically. We used SUPERFISH to accomplish the RF simulations. We present an example of the rf photogun TOPGUN design using these tools.
keywords:
Download | Details | Edit | Delete
title: Start-to-end simulation for the LCLS X-ray FEL
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: Sven Reiche | C. Pellegrini | J.B. Rosenzweig | P. Emma | P. Krejcik
abstract: X-ray FELs, such as the LCLS and TESLA FEL, require electron beams with large peak current and very small emittance. The X-ray peak power, temporal and spectral properties, depend significantly on details of the electron beam phase space distribution. The electron beam distribution is determined by many effects, as the emission process at the gun photo-cathode, bunch compression, acceleration and wakefields within the undulator. Although analytical results can give an estimate of the expected performance, the complexity of the electron beam generation, acceleration and compression can only be evaluated using a numerical simulation of all these processes, a start-to-end simulation. In this presentation we discuss the LCLS X-Ray FEL performance estimated by a start-to-end simulation, and we compare the results with those obtained using a simpler model. (19 References).
keywords:
Download | Details | Edit | Delete
title: Chicane compressor development for BNL ATF- applications to SASE FEL
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
2 authors: R. Agustsson | J.B. Rosenzweig
abstract: A chicane compressor is being designed and constructed at UCLA for implementation at the BNL Accelerator Test Facility. The beam optics, including collective fields, and expected performance of the device has been simulated using TRACE3D and ELEGANT. Based on these studies, as well as constraints due to downstream ATF optics, the chicane magnet specifications were determined. The dipole magnets were designed using AMPERES 3D magnetostatic modeling, and have been constructed. Implementation of this device at the ATF, as well as initial physics experiments on coherent synchrotron radiation emission (and associated emittance growth) at 70 MeV, and expected performance enhancement of the VISA SASE FEL experiment, are discussed.
keywords:
Details | Edit | Delete
title: Ultrafast materials probing with the LLNL Thomson X-ray source
format: conference proceeding
conference: Linear Accelerator Conference 2002
year: 2002
24 authors: A. Tremaine | S. Anderson | W. Brown | C. Barty | R. Cauble | J. Crane | H. Cynn | C. Ebbers | D. Fittinghoff | D. Gibson | F. Hartemann | I. Jovanovich | J. Kuba | G.P. Le Sage | A. McMahan | R. Minich | J. Moriarty | B. Remington | D. Slaughter | P. Springer | F. H. Steitz | C. S. Yoo | J.B. Rosenzweig | T. Ditmire
abstract: The use of short laser pulses to generate very high brightness, ultra short (fs to ps) x-ray pulses is a topic of great interest. In principle, femtosecond-scale pump-probe experiments can be used to temporally resolve structural dynamics of materials on the time scale of atomic motion. The development of sub?ps x-ray pulses will make possible a wide range of materials and plasma physics studies with unprecedented time resolution. PLEIADES (Picosecond Laser Electron Interaction for Dynamic Evaluation of Structures), the Thomson scattering project at LLNL, will provide such a novel x-ray source of high power using short laser pulses and a high brightness, relativistic electron bunch. The system is based on a 5 mm-mrad normalized emittance photoinjector, 100 MeV electron RF linac, and a 300 mJ, 35 fs solid-state laser system. PLEIADES will produce ultra fast pulses with x-ray energies (60 keV) capable of probing into high-Z metals.
keywords:
Download | Details | Edit | Delete
title: Transition radiation for uneven, limited surfaces
format: conference proceeding
conference: PAC 2001
year: 2001
2 authors: Sven Reiche | J.B. Rosenzweig
abstract: In the most common approach to modeling transition radiation, the annihilation of the incident particle with its image particle at the metallic boundary is calculated. This is valid only for ideal planar boundaries, and is not applicable if the surface is modulated, rough or limited in the transverse dimension. In this paper, we show results obtained by replacing the image current with the induced surface charge and surface distributions. Special problems such as a modulated surface are analytically solved and compared to a numerical simulation. Implications for experimental use of transition radiation-based beam monitors are discussed. (9 References).
keywords:
Download | Details | Edit | Delete
title: Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
153 authors: N. D. Arnold | J. Attig | G. Banks | R. Bechtold | K. Beczek | C. Benson | S. Berg | W. Berg | S. G. Biedron | J. A. Biggs | M. Borland | K. Boerste | M. Bosek | W. R. Brzowski | J. Budz | J. A. Carwardine | P. Castro | Y. C. Chae | S. Christensen | C. Clark | M. Conde | E. A. Crosbie | G. A. Decker | R. J. Dejus | H. DeLeon | P. K. Den Hartog | B. N. Deriy | D. Dohan | P. Dombrowski | D. Donkers | C. L. Doose | R. J. Dortwegt | G. A. Edwards | Y. Eidelman | M. J. Erdmann | J. Error | R. Ferry | R. Flood | J. Forrestal | H. Freund | H. Friedsam | J. Gagliano | W. Gai | J. N. Galayda | R. Gerig | R. L. Gilmore | E. Gluskin | G. A. Goeppner | J. Goetzen | C. Gold | A. J. Gorski | A. E. Grelick | M. W. Hahne | S. Hanuska | K. C. Harkay | G. Harris | A. L. Hillman | R. Hogrefe | J. Hoyt | Z. Huang | J. M. Jagger | W. G. Jansma | M. Jaski | S. J. Jones | R. T. Keane | A. L. Kelly | C. Keyser | K. J. Kim | S. H. Kim | M. Kirshenbaum | J. H. Klick | K. Knoerzer | R. J. Koldenhoven | M. Knott | S. Labuda | R. Laird | J. Lang | F. Lenkszus | E. S. Lessner | J. W. Lewellen | Y. Li | R. M. Lill | A. H. Lumpkin | O. A. Makarov | G. M. Markovich | M. McDowell | W. P. McDowell | P. E. McNamara | T. Meier | D. Meyer | W. Michalek | S. V. Milton | H. Moe | E. R. Moog | L. Morrison | A. Nassiri | J. R. Noonan | R. Otto | J. Pace | S. J. Pasky | J. M. Penicka | A. F. Pietryla | G. Pile | C. Pitts | J. Power | T. Powers | C. C. Putnam | A. J. Puttkammer | D. Reigle | L. Reigle | D. Ronzhin | E. R. Rotela | E. F. Russell | V. Sajaev | S. Sarkar | J. C. Scapino | K. Schroeder | R. A. Seglem | N. S. Sereno | S. K. Sharma | J. F. Sidarous | O. Singh | T. L. Smith | R. Soliday | G. A. Sprau | S. J. Stein | B. Stejskal | V. Svirtun | L. C. Teng | E. Theres | M.C. Thompson | B. J. Tieman | J. A. Torres | E. M. Trakhtenberg | G. Travish | G. F. Trento | J. Vacca | I. B. Vasserman | N. A. Vinokurov | D. R. Walters | Wang, J. | X. J. Wang | J. Warren | S. Wesling | D. L. Weyer | G. Wiemerslage | K. Wilhelmi | R. Wright | D. Wyncott | S. Xu | B. X. Yang | W. Yoder | R. B. Zabel
abstract: Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations. (31 References).
keywords:
Download | Details | Edit | Delete
title: Proposal for a IR Waveguide SASE FEL at the PEGASUS Injector
format: conference proceeding
conference: PAC 2001
year: 2001
3 authors: Sven Reiche | J.B. Rosenzweig | S. Telfer
abstract: Free Electron Lasers up to the visible regime are dominated by diffraction effects, resulting in a radiation size much larger than the electron beam. Thus the effective field amplitude at the location of the electron beam, driving the FEL process, is reduced. By using a waveguide, the radiation field is confined within a smaller aperture and an enhancement of the FEL performance can be expected. The PEGASUS injector at UCLA will be capable to provide the brilliance needed for an IR SASE FEL. The experiment PERSEUS (Power Enhanced Radiation Source Experiment Using Structures) is proposed to study the physics of a waveguide SASE FEL in a quasi 1D environment, where diffraction effects are strongly reduced as it is the case only for future FELs operating in the VUV and X-ray regime. The expected FEL performance is given by this presentation.
keywords:
Download | Details | Edit | Delete
title: Initial gain measurements of an 800 nm SASE FEL, VISA
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
26 authors: P. Frigola | A. Murokh | P. Musumeci | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | A. Tremaine | M. Babzien | I. Ben-Zvi | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X. J. Wang | K. A. Van Bibber | L. Bertolini | J. M. Hill | G.P. Le Sage | M. Libkind | A. Toor | R. Carr | M. Cornacchia | L. Klaisner | H. D. Nuhn | Ruland, R. | D. C. Nguyen
abstract: The visible to infrared SASE amplifier (VISA) FEL is designed to obtain high gain at a radiation wavelength of 800 nm. The FEL uses the high brightness electron beam of the accelerator test facility (ATF), with energy of 72 MeV. VISA uses a novel, 4 m long, strong focusing undulator with a gap of 6 mm and a period of 1.8 cm. To obtain large gain the beam and undulator axis have to be aligned to better than 5 mu m. Results from initial measurements on the alignment, gain, and spectrum will be presented and compared to theoretical calculations and simulations. (10 References).
keywords:
Download | Details | Edit | Delete
title: Design considerations for a SASE X-ray FEL
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
1 author: C. Pellegrini
abstract: The well developed theory of short wavelength SASE-FELs is now being used to design two X-ray lasers, LCLS and Tesla-FEL. However, the physics and technology of these projects present some unique challenges, related to the very high peak current of the electron beam, the very long undulator needed to reach saturation, and the importance of preserving the beam phase-space density even in the presence of large wake-field effects. In the first part of the paper, we review the basic elements of the theory, the scaling laws for an X-ray SASE-FEL, and the status of the experimental verification of the theory. We then discuss some of the most important issues for the design of these systems, including wake-field effects in the undulator, and the choice of undulator type and beam parameters. (74 References).
keywords:
Download | Details | Edit | Delete
title: Monitoring and manipulation of sub-picosecond beams
format: conference proceeding
conference: PAC 2001
year: 2001
1 author: J.B. Rosenzweig
abstract: In cutting-edge applications such as advanced accelerators and free-electron lasers, very high brightness beams of duration shorter than a picosecond are required. Further, these applications demand specific types of longitudinal beam profiles, such as pulse trains, and ramped pulses. The production of such types of beams present challenges both in technique, and in the instrumentation required to verify the method employed. The techniques for producing such short beams which have received the most investigation in recent years include chicane compression, and modulation via free-electron laser mechanism and its inverse. We discuss the principles and relevant single particle and collective effects which impact their performance. We review progress in implementing these schemes, as well as newer concepts such as relativistic velocity bunching and use of negative R_56 compressors. We also discussed the challenges in diagnosing these state-of-the-art beam systems.
keywords:
Download | Details | Edit | Delete
title: Optimization of an x-ray SASE-FEL
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
7 authors: C. Pellegrini | Sven Reiche | J.B. Rosenzweig | C. Schroeder | A. A. Varfolomeev | Tolmachev, S. | H. D. Nuhn
abstract: The most important characteristics of an X-ray SASE-FEL are determined by the electron beam energy, transverse and longitudinal emittance, and by choice of the undulator period, field, and gap. Among them are the gain and saturation length, the amount and spectral characteristics of the spontaneous radiation, the wake fields due to the vacuum pipe. The spontaneous radiation intensity is very large in all X-ray SASE-FELs now being designed, and it contributes to the final electron beam energy spread, thus affecting the gain. It also produces a large background for the beam and radiation diagnostics instrumentation. The wake fields due to the resistivity and roughness of the beam pipe through the undulator, also affects the beam 6-dimensional phase space volume, and thus the gain and the line width. In this paper, we discuss ways to optimize the FEL when considering all these effects. In particular we consider and discuss the use of a hybrid iron-permanent magnet helical undulator to minimize some of these effects, and thus optimize the FEL design.
keywords:
Download | Details | Edit | Delete
title: Chirped-beam two-stage SASE-FEL for high power femtosecond X-ray pulse generation
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: C.B. Schroeder | C. Pellegrini | S. Reiche | J. Arthur | P. Emma
abstract: We present a method for generating femtosecond duration X-ray pulses using a single-pass free-electron laser (FEL). This method uses an energy-chirped electron beam to produce a frequency-chirped X-ray pulse through self-amplified spontaneous emission (SASE). After the undulator we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse, and therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE-FEL, and consider the performance of the chirped-beam two-stage option for the for the Linac Coherent Light Source (LCLS).
keywords:
Download | Details | Edit | Delete
title: Proposal for a IR waveguide SASE FEL at the PEGASUS injector
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
3 authors: Sven Reiche | J.B. Rosenzweig | S. Telfer
abstract: Free Electron Lasers up to the visible regime are dominated by diffraction effects, resulting in a radiation size much larger than the electron beam. Thus the effective field amplitude at the location of the electron beam, driving the FEL process, is reduced. By using a waveguide, the radiation field is confined within a smaller aperture and an enhancement of the FEL performance can be expected. The PEGASUS injector at UCLA will be capable to provide the brilliance needed for an IR SASE FEL. The experiment Power Enhanced Radiation Source Experiment Using Structures (PERSEUS) is proposed to study the physics of a waveguide SASE FEL in a quasi I D environment, where diffraction effects are strongly reduced as it is the case only for future FELs operating in the VUV and X-ray regime. The expected FEL performance is given by this presentation.
keywords:
Download | Details | Edit | Delete
title: Saturnus: the UCLA compact high-brightness linac
format: conference proceeding
conference: Conference on High-Brightness Beams for Advanced Accelerator Applications
year: 1992
1 author: C. Pellegrini
abstract: Saturnus is a compact S-band linac designed to produce a single bunch with an energy of 20 MeV, a peak current larger than 200 A on energy spread of 0.3%, an emittance smaller than 5 mm mrad (normalized rms), and a pulse duration of 4 ps or shorter. This bunch can be followed at a variable distance by a second weak 'witness' bunch, to be used to measure the field excited by the first bunch,. The linac electron injector is based on the Brookhaven photoinjector design. Solenoids are used to focus the beam from the gun through a mirror box and a plane wave transformer accelerating structure. The linac will be followed by two beam lines, one of them capable of longitudinal bunch compression, leading to experimental stations where beam-laser and beam plasma interactions will be studied. (4 References).
keywords:
Download | Details | Edit | Delete
title: Inverse Free Electron Laser Experiment at the Neptune Laboratory
format: conference proceeding
conference: AAC 2002 10th
year: 2002
6 authors: P. Musumeci | C. Pellegrini | J.B. Rosenzweig | A. A. Varfolomeev | Tolmachev, S. | T. Yarovoi
abstract: We present an Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Laboratory. This experiment will use a 1 TW CO2 laser to accelerate through two strongly tapered undulators an electron beam from 16 MeV up to 5 MeV. The scheme proposed is the diffraction dominated IFEL interaction. The Raleigh range of the laser beam is about 2 cm, much shorter than the interaction length (the undulator length is 50 cm). In this regime adiabatic capture is possible in the first part of the undulator. In the focus region, we propose a solution to the problem of the dephasing between electrons and photons due to the
keywords:
Download | Details | Edit | Delete
title: The BESSY FEL Project
format: conference proceeding
conference: FEL 2001 23rd
year: 2002
20 authors: M. Abo-Bakr | W. Anders | J. Bahrdt | R. Bakker | W. Eberhardt | B. Faatz | R. Follath | A. Gaupp | M. v. Hartrott | E. Jaeschke | D. Kraemer | P. Kuske | M. Martin | R. Mueller | H. Prange | Sven Reiche | W. Sandner | F. Senf | I. Will | G. Wustefeld
abstract: Berliner Elektronenspeicherring-Gesellschaft fur Synchrotronstrahlung (BESSY) plans to construct a linac-based single-pass FEL as an addition to its existing third generation storage-ring-based light-source. The project aims to obtain an FEL-based user-facility that covers the VUV and soft X-ray spectral range (20 eV less than or equal to homega less than or equal to 1 keV). At present, the design stage is funded as a collaboration between BESSY, DESY, the Hahn-Meitner-Institute in Berlin, and the Max-Born-Institute in Berlin. This stage focuses on optimization of the FEL as a user light-source, both with respect to its capabilities and in its performance. Important issues are: stability, seeding options of the SASE FEL, wavelength-tunability, synchronization with external laser sources and, on a longer time-scale, the generation of ultra-short (< 20 fs RMS) optical pulses.
keywords:
Download | Details | Edit | Delete
title: Status of the 3D Time-Dependent FEL Simulation Code GENESIS 1.3
format: conference proceeding
conference: FEL 2001 23rd
year: 2002
2 authors: Sven Reiche | B. Faatz
abstract: Since its release in 1999 the 3D time-dependent code GENESIS 1.3 has become a helpful tool for the design-studies and analysis of a single-pass Free-Eelectron Lasers experiments. With the latest version new features have been added such as support for wake-fields and incoherent spontaneous radiation. In addition the more modular structure of the open-source code and the improved support of external imput files allow a better understanding of the code, supporting users who want to add new features to the code.
keywords:
Download | Details | Edit | Delete
title: Collective instabilities in accelerator and storage rings
format: conference proceeding
conference: Andrew Sessler Symposium on the Physics of Beams
year: 1996
1 author: C. Pellegrini
abstract: We describe the initial discovery of collective beam instability in accelerator and storage rings, the work that was done in the 60's to obtain a theory of these effects, and their impact on the developments of electron-positron and proton-proton colliders.
keywords:
Download | Details | Edit | Delete
title: Energy Loss of a High Charge Bunched Electron Beam in Plasma: Nonlinear plasma response and linear scaling
format: conference proceeding
conference: AAC 2002 10th
year: 2002
4 authors: J.B. Rosenzweig | N. Barov | M.C. Thompson | R.B. Yoder
abstract: There has been much experimental and theoretical interest in blowout regime of plasma wakefield acceleration (PWFA), which features ultra-high accelerating fields, linear transverse focusing forces, and nonlinear plasma motion. Using an exact analysis, we examine here a fundamental limit of nonlinear PWFA excitation, by an infinitesimally short, relativistic electron beam. The beam energy loss in this case is shown to be linear in charge even for nonlinear plasma response, where a normalized, unitless charge exceeds unity, and relativistic plasma effects become important or dominant. The physical bases for this persistence of linear response are pointed out. As a byproduct of our analysis, we re-examine the issue of field divergence as the point-charge limit is approached, suggesting an important modification of commonly held views of evading unphysical energy loss. Deviations from linear behavior are investigated using simulations with finite length beams. The peak accelerating field in the plasma wave excited behind a finite-length beam is also examined, with the artifact of wave spiking adding to the apparent persistence of lin