Section Navigation

Browse



logged in as: pbpl
logout
list users

183 journal articles:

Edit | List
title: TREDI: fully 3D beam dynamics simulation of RF guns, bendings and FELs
format: journal article
publisher: Nuclear Instruments & Methods in Physics Research
year: 1999
3 authors: L. Giannessi | P. Musumeci | M. Quattromini
abstract: We describe a three-dimensional code modelling the propagation of charged beams in accelerator devices. The inclusion of space charge fields is taken into account by means of the Lienard-Wiechert retarded potentials. As an illustration of the capabilities of the program, the results of a simulation are given that, describe the beam dynamics from the cathode to the undulator through the whole accelerating system. Evidence of bunching in the undulator, as an indication of SASE is observed.
keywords:
Download | Details | Edit | Delete
title: X-ray free-electron lasers- principles, properties and applications
format: journal article
publisher: Nuclear Instruments & Methods in Physics Research
year: 2003
2 authors: C. Pellegrini | J. Stoehr
abstract: With advances in technology, it is now possible to realize the dream of fully coherent X-ray laser.
keywords:
Download | Details | Edit | Delete
title: Chirped-beam two-stage free-electron laser for high-power femtosecond x-ray pulse generation
format: journal article
publisher: Journal of the Optical Society of America B-Optical Physics
year: 2002
5 authors: C. B. Schroeder | C. Pellegrini | Sven Reiche | J. Arthur | P. Emma
abstract: A method for generating femtosecond-duration x-ray pulses with a free-electron laser is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped x-ray pulse by self-amplified spontaneous emission. A short temporal pulse is created by use of a monochromator to select a narrow radiation bandwidth. A second undulator is used to amplify the short-duration radiation. The radiation characteristics produced by a chirped-beam two-stage free-electron laser are calculated, and the performance of the chirped-beam two-stage option for the Linac Coherent Light Source is considered.
keywords:
Download | Details | Edit | Delete
title: Terawatt x-ray free-electron-laser optimization by transverse electron distribution shaping
format: journal article
publisher: Physical Review Accelerators and Beams
year: 2014
6 authors: C. Emma | J. Wu | K. Fang | S. Chen | S. Serkez | C. Pellegrini
abstract: We study the dependence of the peak power of a 1.5 Å Terawatt (TW), tapered x-ray free-electron laser (FEL) on the transverse electron density distribution. Multidimensional optimization schemes for TW hard x-ray free-electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to a Gaussian distribution. The optimizations are performed for a 200 m undulator and a resonant wavelength of λr=¼1.5Å using the fully three-dimensional FEL particle code GENESIS. The study shows that the flatter transverse electron distributions enhance optical guiding in the tapered section of the undulator and increase the maximum radiation power from a maximum of 1.56 TW for a transversely Gaussian beam to 2.26 TW for the parabolic case and 2.63 TW for the uniform case. Spectral data also shows a 30% – 70% reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian. An analysis of the transverse coherence of the radiation shows the coherence area to be much larger than the beam spotsize for all three distributions, making coherent diffraction imaging experiments possible.
keywords:
Download | Details | Edit | Delete
title: Generation of sub-picosecond electron bunches from RF photoinjectors
format: journal article
publisher: Nuclear Instruments & Methods in Physics Research
year: 1997
3 authors: L. Serafini | R. Zhang | C. Pellegrini
abstract: In this paper we discuss the possibility to generate sub-picosecond electron bunches directly from a photoinjector by illuminating a photo-cathode in an RF cavity with a phase-locked sub-picosecond laser pulse. In particular, we address all de-bunching effects taking place during acceleration and transport through a photoinjector. We provide analysis of the beam dynamics, as well as the comparison with numerical simulations. 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. (23 References).
keywords:
Download | Details | Edit | Delete
title: Horizontal Phase-Space Distortions Arising from Magnetic Pulse Compression of an Intense, Relativistic Electron Beam
format: journal article
publisher: Physical Review Letters
year: 2003
4 authors: S. Anderson | J.B. Rosenzweig | P. Musumeci | M.C. Thompson
abstract: We report detailed measurements of the transverse phase space distortions induced by magnetic chicane compression of a high brightness, relativistic electron beam to subpicosecond length. A strong bifurcation in the phase space is observed when the beam is strongly compressed. This effect is analyzed using several computational models and is correlated to the folding of longitudinal phase space. The impact of these results on current research in collective beam effects in bending systems and implications for future short wavelength free-electron lasers and linear colliders are discussed.
keywords:
Download | Details | Edit | Delete
title: Report of the U.S. Department of Energy Fusion Energy Sciences Advisory Committee (FESAC) panel reviewing the theory and computing program
format: journal article
publisher: Journal of Fusion Energy
year: 2000
16 authors: J. Sheffield | T. M. Antonsen | L. A. Berry | M. R. Brown | J. P. Dahlburg | R. C. Davidson | M. Greenwald | C. C. Hegna | W. McCurdy | D. E. Newman | C. Pellegrini | C. K. Phillips | D. E. Post | M. N. Rosenbluth | T. C. Simonen | J. Van Dam
abstract: This Panel was set up by the Fusion Energy Sciences Advisory Committee (FESAC) at its November 2000 meeting for the purpose of addressing questions from the Department of Energy concerning the theory and computing/simulation program of the Office of Fusion Energy Sciences. Although the Panel primarily addressed programmatic questions, it acknowledges that the theory and computing in fusion energy sciences has a stellar record of research successes. (A recent FESAC report entitled "Opportunities in the Fusion Energy Sciences Program" listed a number of theory and computing research highlights.) Last year the National Research Council performed an assessment of the quality of the fusion energy sciences program-including theory and computing-and concluded that the quality of its research is on a par with that of other leading areas of contemporary physical science.
keywords:
Download | Details | Edit | Delete
title: Nonequilibrium transverse motion and emittance growth in ultrarelativistic space-charge dominated beams
format: journal article
publisher: Physical Review Special Topics-Accelerators & Beams
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. These results are discussed within the context of recent ultrahigh brightness RF photoinjector designs. (20 References).
keywords:
Download | Details | Edit | Delete
title: Plasma Electron Trapping and Acceleration in a Plasma Wake Field Using a Density Transition
format: journal article
publisher: Physical Review Letters
year: 2001
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 single, short electron pulse travels through an underdense plasma with a sharp, localized, downward density transition. Near this transition, a number of background plasma electrons are trapped in the plasma wake field, due to the rapid wavelength increase of the induced wake wave in this region. The viability of this scheme is verified using two-dimensional particle-in-cell simulations. To investigate the trapping and acceleration mechanisms further, a 1D Hamiltonian analysis, as well as 1D simulations, has been performed, with the results presented and compared.
keywords:
Download | Details | Edit | Delete
title: Space-charge effects in high brightness electron beam emittance measurements
format: journal article
publisher: Physical Review Special Topics-Accelerators & Beams
year: 2002
4 authors: S. Anderson | J.B. Rosenzweig | G.P. Le Sage | J. K. Crane
abstract: The measurement of emittance in space-charge dominated, high brightness beam systems is investigated from conceptual, computational, and experimental viewpoints. As the self-field-induced collective motion in the low energy, high brightness beams emitted from photoinjector rf guns are more important in determining the macroscopic beam evolution than thermal spreads in transverse velocity; traditional methods for phase space diagnosis fail in these systems. We discuss the role of space charge forces in a traditional measurement of transverse emittance, the quadrupole scan. The mitigation of these effects by use of multislit- or pepper-pot-based techniques is explained. The results of a direct experimental comparison between quadrupole scanning and slit-based determination of the emittance of a 5 MeV high brightness electron beam are presented. These data are interpreted with the aid of both envelope and multiparticle simulation codes. It is shown that the ratio of the beam's beta function to its transverse plasma wavelength plays a central role in the quadrupole scan results. Methods of determining the presence of systematic errors in quadrupole scan data are discussed.
keywords:
Download | Details | Edit | Delete
title: Plasma source test and simulation results for the underdense plasma lens experiment at the UCLA Neptune Laboratory
format: journal article
publisher: IEEE Transactions on Plasma Science
year: 2000
8 authors: H. Suk | C. E. Clayton | C. Joshi | T.C. Katsouleas | P. Muggli | R. Narang | C. Pellegrini | J.B. Rosenzweig
abstract: The planned plasma lens experiment at the UCLA Neptune Laboratory is described. In the experiment, electron beams with an energy of 16 MeV, a charge of 4 nC, and a pulse duration of 30 ps full-width at half-maximum (FWHM) are designed to be produced from the 1.625-cell photoinjector radio-frequency gun (f=2.856 GHz) and PWT linac in the Neptune. The generated beams are passed through a thin plasma with a density of low 10/sup 12/ cm/sup -3/ range and a thickness of a few centimeters. For this experiment, a LaB/sub 6/-based discharge plasma source was developed and tested. In this paper, the overview of the planned plasma lens experiment and the test results of the plasma source for various conditions are presented. In addition, computer simulations with a 2-1/2 dimensional particle-in-cell code (MAGIC) were performed and the simulation results are shown. (19 References).
keywords:
Download | Details | Edit | Delete
title: Propagation of short electron pulses in a plasma channel
format: journal article
publisher: Physical Review Letters
year: 1998
4 authors: N. Barov | M. E. Conde | W. Gai | J.B. Rosenzweig
abstract: We report the near-steady-state propagation over long distance of a 25 psec, tightly focused relativistic electron beam which creates, by radial ejection of plasma electrons, a focusing ion channel in a plasma of electron density smaller than the beam. A dense beam core, close in radius to the injected beam, which was nearly matched to the ion focusing strength, is observed at the plasma exit. Time-resolved imaging confirms that this core is situated in the trailing half of the beam, as predicted by analytical and computer models. We discuss the impact of these results on plasma wake field acceleration schemes. (16 References).
keywords:
Download | Details | Edit | Delete
title: Propagation of short electron pulses in underdense plasmas
format: journal article
publisher: Physical Review E
year: 1994
2 authors: N. Barov | J.B. Rosenzweig
abstract: Dense relativistic electron beams traversing a plasma, in what is known as the underdense, or ion focusing, regime experience a strong, linear transverse restoring force. This force arises from the nearly immobile ions which form a channel of uncompensated positive charge when the plasma electrons are ejected in response to the introduction of the beam charge. This phenomenon can be used for focusing the electron beam to very high densities over long propagation distances. Several schemes have been proposed, including the nonlinear plasma wake-field accelerator, the adiabatic plasma lens, and the ion-channel laser, whose viability is based on this focusing effect for very short pulse, high current electron beams propagating in plasma. In this paper we examine, analytically and numerically, the self-consistent requirements on plasma density, beam current, length, and transverse emittance which must be satisfied in order for ion-channel formation and near equilibrium beam propagation to exist over the majority of the length of the electron beam. The dynamics of the beam-plasma system are modeled by a simultaneous solution of the plasma electron cold-fluid equations, and the Maxwell-Vlasov equation governing the beam's thermal equilibrium. The effects of introducing a strong axial magnetic field on the plasma response and beam equilibria are examined. In addition to developing criteria for self-consistent equilibrium focusing, a time-dependent analysis where the beam particles are treated as mobile particles in cells is developed in order to study the dynamical approach of this equilibrium. Inherently time-dependent phenomena, such as matching of the beam into the plasma and adiabatic lenses, are then examined with this method.
keywords:
Download | Details | Edit | Delete
title: Electromagnetic wake fields and beam stability in slab-symmetric dielectric structures
format: journal article
publisher: Physical Review E
year: 1997
3 authors: A. Tremaine | J.B. Rosenzweig | P. Schoessow
abstract: Several promising schemes for high-gradient acceleration of charged particles in slab-symmetric 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 by a relativistic charged particle beam in a planar structure. We show that in the limit of an infinitely wide beam the net deflecting wake fields vanishes. This result is verified in the limit of a large aspect ratio (sheet) beam by finite beam analysis based on a Fourier decomposition of the current profile, as well as a paraxial wave analysis of the wake fields driven by Gaussian profile beams. The Fourier analysis forms the basis of an examination of flute instability in the sheet beam system. Practical implications of this result for beam stability and enhanced current loading in short-wavelength advanced accelerators are discussed.
keywords:
Download | Details | Edit | Delete
title: Observation of plasma wakefield acceleration in the underdense regime
format: journal article
publisher: Physical Review Special Topics-Accelerators & Beams
year: 2000
5 authors: N. Barov | J.B. Rosenzweig | M. E. Conde | W. Gai | J. G. Power
abstract: Initial experiments which have explored the physics of the underdense (blowout) regime of the plasma wakefield accelerator (PWFA) at the Argonne Wakefield Accelerator facility are reported. In this regime, the relativistic electron beam is denser than the plasma, causing the beam channel to completely rarefy, and leaving a high quality accelerating region which also contains a uniform ion column. This ion column in turn allows the drive and accelerating beams to be well guided over many initial beam beta-function lengths. The results of these experiments, which have taken place over several years, are reviewed. Notable achievements in the course of these studies include the creation and measurement of drive and witness beam generated in an rf photoinjector, as well as previously published studies on drive beam guiding in the underdense regime. In addition, these experiments allowed measurement of both beam energy loss and gain, at a maximum average rate of 25 MeV/m in this regime of the PWFA, which is consistent with a peak acceleration gradient of 62 MeV/m in the excited waves. Difficulties associated with this type of experiment are discussed, as are prospects for mitigating these difficulties and achieving high gradient acceleration in planned future experiments.
keywords:
Download | Details | Edit | Delete
title: Observation of Self-Amplified Spontaneous-Emission-Induced Electron-Beam Microbunching Using Coherent Transition Radiation
format: journal article
publisher: Physical Review Letters
year: 1998
9 authors: A. Tremaine | J.B. Rosenzweig | S. Anderson | Pedro Frigola | M. Hogan | A. Murokh | C. Pellegrini | D. C. Nguyen | R. L. Sheffield
abstract: We report the measurement of electron-beam microbunching at the exit of a self-amplified spontaneous-emission free-electron laser (SASE FEL), by observation of coherent transition radiation (CTR). The CTR was found to have an angular spectrum much narrower than spontaneous transition radiation and a narrow-band frequency spectrum. The central frequency of the fundamental CTR spectrum is found to differ slightly from that of the SASE, a finding in disagreement with previously invoked CTR theory. The CTR measurement establishes the uniformity of microbunching in the transverse dimension, indicating the SASE FEL operates in a dominant transverse mode.
keywords:
Download | Details | Edit | Delete
title: Fundamental and harmonic microbunching in a high-gain self-amplified spontaneous-emission free-electron laser
format: journal article
publisher: Physical Review E
year: 2002
13 authors: A. Tremaine | X.J. Wang | M. Babzien | I. Ben-Zvi | M. Cornacchia | A. Murokh | H. D. Nuhn | R. Malone | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | J. Skaritka | V. Yakimenko
abstract: Electron beam microbunching in both the fundamental and second harmonic in a high-gain self-amplified spontaneous emission free-electron laser (SASE FEL) was experimentally characterized using coherent transition radiation. The microbunching factors for both modes (b1 and b2) approach unity, an indication of FEL saturation. These measurements are compared to the predictions of FEL simulations. The simultaneous capture of the microbunching and SASE radiation for individual micropulses correlate the longitudinal electron beam structure with the FEL gain.
keywords:
Download | Details | Edit | Delete
title: Spectrum, temporal structure, and fluctuations in a high-gain free-electron laser starting from noise
format: journal article
publisher: Physical Review Letters
year: 1994
5 authors: R. Bonifacio | L. De Salvo | P. Pierini | N. Piovella | C. Pellegrini
abstract: We study the time structure, the frequency composition, and the shot to shot fluctuations of the radiation emitted by a free-electron laser starting from shot noise in the electron beam longitudinal distribution, taking into account slippage and finite bunch length effects. We find a very different behavior when the bunch length, l/sub b/, is much longer than the cooperation length, l/sub c/, or of the order of a few l/sub c/. The field evolution is dominated by slippage effects in both cases, and shows the presence of superradiant spikes. (14 References).
keywords:
Download | Details | Edit | Delete
title: Experimental characterization of nonlinear harmonic radiation from a visible self-amplified spontaneous emission free-electron laser at saturation
format: journal article
publisher: Physical Review Letters
year: 2002
12 authors: A. Tremaine | X.J. Wang | M. Babzien | I. Ben-Zvi | M. Cornacchia | H. D. Nuhn | R. Malone | A. Murokh | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | V. Yakimenko
abstract: Nonlinear harmonic radiation was observed using the VISA self-amplified, spontaneous emission (SASE) free-electron laser (FEL) at saturation. The gain lengths, spectra, and energies of the three lowest SASE FEL modes were experimentally characterized. The measured nonlinear harmonic gain lengths and center spectral wavelengths decrease with harmonic number, n, which is consistent with nonlinear harmonic theory. Both the second and third nonlinear harmonics energies are about 1% of the fundamental energy. These experimental results demonstrate for the first time the feasibility of using nonlinear harmonic SASE FEL radiation to produce coherent, femtosecond X-rays. (33 References).
keywords:
Download | Details | Edit | Delete
title: Study of a novel compact standing wave RF linac
format: journal article
publisher: Nuclear Instruments & Methods in Physics Research
year: 1997
3 authors: R. Zhang | C. Pellegrini | R. Cooper
abstract: A novel, compact RF linac structure, the plane wave transformer (PWT), is studied. The PWT provides high accelerating field and high efficiency, and can be used to accelerate high-brightness beams. PWT linac prototypes with eight cells at S-band have been developed at UCLA and successfully used to accelerate an electron beam by more than 10 MeV in 40 cm. In this paper, we describe the principal properties of this structure, the electric parameters obtained from numerical simulation, and measurement results from microwave cold tests. The mechanical design for prototype linacs is also reported. (13 References).
keywords:
Download | Details | Edit | Delete
title: Plasma density transition trapping as a possible high-brightness electron beam source
format: journal article
publisher: PHYSICAL REVIEW SPECIAL TOPICS - ACCELERATORS AND BEAMS
year: 2004
3 authors: M.C. Thompson | J.B. Rosenzweig | Suk, H.
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 x 10^14 A/(mrad)^2. A proof-of principle transition trapping experiment is planned for the near future. The proposed experiment is described in detail.
keywords:
Download | Details | Edit | Delete
title: Beam amplitude behavior upon crossing a linear coupling resonance with damping in one dimension
format: journal article
publisher: IEEE Transactions on Nuclear Science
year: 1969
4 authors: M. Lee | E. D. Courant | C. Pellegrini | A. M. Sessler
abstract: A study has been conducted to investigate theoretically the effects of vertical damping on the betatron oscillations for particles passing through a resonance. This report describes a calculation for a single-particle model and for the case of the upsilon /sub 1/+ upsilon /sub 2/=1 resonance.
keywords:
Download | Details | Edit | Delete
title: Side-Coupled Slab-Symmetric Structure for High-Gradient Acceleration using Terahertz Power
format: journal article
publisher: PHYSICAL REVIEW SPECIAL TOPICS - ACCELERATORS AND BEAMS
year: 2005
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 described. The device is resonantly excited by an external drive laser which is side coupled into the acceleration region; a novel coupling scheme, which consists of an array of narrow, equally spaced slots in the upper structure boundary, is presented and analyzed in detail. This structure partakes of the advantages of earlier slab-symmetric optical acceleration proposals, but will use a terahertz-frequency external radiation source ( 340 m), allowing realistic electron beams to be used in a proof-of-principle experiment. Two- and three-dimensional electromagnetic simulations are used to verify the mode patterns and study the effects of the couplers, including time-dependent calculations of the filling of the structure and particle-in-cell computations of the beam wakefields. Details of the resonance are found to be highly sensitive to the coupling slot geometry: the presence of the couplers can lead to frequency detuning, changes in the field breakdown limits and overall Q factor, and distortions of the field pattern. Beam wakefields are enhanced by the presence of the slots, but found to have no significant effect on the beam transport. The resonant accelerating fields, which are nearly constant along the short transverse direction, are found to have between 10 and 15 times the amplitude of the driving radiation, with only a small ( < 10%) admixture of other nonaccelerating modes. Field gradients are computed to be near 100 MV=m when the structure is driven with 100MWof terahertz laser power. Possible manufacturing methods for a prototype device are discussed.
keywords:
Download | Details | Edit | Delete
title: A Simple Calculation of Electron and Lattice Heating in the UCLA RF Photocathode
format: journal article
publisher:
year: December 17, 1992
1 author: J.B. Rosenzweig
abstract: It has been suggested by C. Joshi that the source of pulse lengthening in the electon beam emitted from the UCLA rf photocathode is due to the heating of the conduction electrons in the copper by the laser pulse. The proposed mechanism for continued emission after the end of the laser is thermally enhanced field emission. Simple calculations (see below) indicate that the temperature rise associated with the laser power deposition could be, in the absence of diffusion and coupling to the ions, in excess of 1000 degrees Kelvin, a temperature which could indeed allow emission. In addition, there have been experiments on this films have shown that this elevated termperature can persist for many picoseconds after the laser is no longer on. The purpose of this note is to explore, using a simple model based on the heat equations for the electrons and the ion lattice, and an even more simplified numerical solution of these coupled differential equations, the heating, as well as the diffusion and coupling of this heat, in our cathode.
keywords:
Details | Edit | Delete
title: The Effects of Ion Motion in Very Intense Beam-driven Plasma Wakefield Accelerators
format: journal article
publisher: Physical Review Letters
year: 2004
4 authors: J.B. Rosenzweig | A.M. Cook | M.C. Thompson | R.B. Yoder
abstract: Recent proposals for using plasma wakefield accelerators in the blowout regime as a component of a linear collider have included very intense driver and accelerating beams, which have densities many times in excess of the ambient plasma density. The electric fields of these beams are widely known to be large enough to completely expel plasma electrons from the beam path; the expelled electrons often attain relativistic velocities in the process. We examine here another aspect of this high-beam density scenario: the motion of ions. In the lowest order analysis, for both cylindrically symmetric and
keywords:
Download | Details | Edit | Delete
title: Electon Micrographs of Copper Photocathodes
format: journal article
publisher:
year: April 1, 1993
1 author: J.B. Rosenzweig
abstract: Electron micrographs of both the damaged copper photocathode from the initial (September 92/April 93) run, a new unannealed cathode, and the new annealed and polished photocathode were obtained to characterize the photoemitting surfaces. These micrographs were produced by a scanning electron microscope (Cambridge (now owned by Leica) model Stereoscan 250) in the materials science department. The samples were held in place with a stainless steel holder with set screws, which allowed good electrical contact and the ability to rotate the cathodes to large angle with respect to vertical. These micrographs were performed with the idea of quantifying relevant surface features wich could be important in such phenomena as electric field enhancement, anomalous absorption of laser light, and surface plasmon excitation.
keywords:
Details | Edit | Delete
title: Properties of the ultrashort gain length, self-amplified spontaneous emission free-electron laser in the linear regime and saturation
format: journal article
publisher: Physical Review E
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. The experiment was performed at the Accelerator Test Facility at BNL, using a high brightness 70-MeV electron beam. A gain length shorter than 18 cm has been obtained, yielding a total 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. Results are compared to the three-dimensional SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL systems. An agreement between simulations and experimental results has been obtained at an unprecedented level of detail.
keywords:
Download | Details | Edit | Delete
title: Pulse Compression in TTF Injector II
format: journal article
publisher:
year: December 13, 1994
1 author: J.B. Rosenzweig
abstract: While the description of longitudinal dynamics of a beam in an rf photoinjector is in general quite complicated, the problem is straightforward after some simplifying assumptions. It is in fact an excellent assumption, that after acceleration to moderately high energy, where the longitudinal phoase space structure is well approximated by that of a beam which has passed throught the accelerating cavities at the speed of light. Under this assumption, each electron has a final energy given by ...
keywords:
Details | Edit | Delete
title: First results from bent crystal extraction at the Fermilab Tevatron
format: journal article
publisher: Nuclear Instruments & Methods B
year: 1996
27 authors: C.T. Murphy | R. Carrigan | D. Chen | G. Jackson | N. Mokhov | H. J. Shih | B. Cox | V. Golovatyuk | A. McManus | A. Bogacz | D. B. Cline | S. Ramachandran | J. Rhoades | J.B. Rosenzweig | B. Newberger | J. A. Ellison | S. Baker | C. R. Sun | W. Gabella | E. Tsyganov | A. Taratin | A. Asseev | V. Biryukov | A. Khanzadeev | T. Prokofieva | V. Samsonov | G. Solodov
abstract: First results from Fermilab Experiment 853 are presented. E853 is an experiment to test the feasibility and efficiency of extracting a low-intensity beam from the halo of the Tevatron using channeling in a bent silicon crystal. The motivation of the experiment is to apply crystal extraction to trans-TeV accelerators like the LHC. Extensive simulation work has been carried out. Two accelerator operating modes have been developed for crystal studies, ''kick'' mode and diffusion mode. Results from the first successful extraction in kick mode are presented.
keywords:
Download | Details | Edit | Delete
title: Generation of high-intensity coherent radiation in the soft-X-ray and vacuum-ultraviolet region
format: journal article
publisher: Journal of the Optical Society of America B-Optical Physics
year: 1985
2 authors: J.B. Murphy | C. Pellegrini
abstract: An electron beam can be made to interact with an undulator magnet so that a collective unstable mode is excited. In this mode, the beam generates coherent radiation whose wavelength is determined by the undulator period and the electron energy. By proper choice of the electron-beam energy, energy dispersion, and density, one can obtain coherent radiation in the soft-X-ray region with peak and average power of the order of hundreds of megawatts and hundreds of milliwatts, respectively. Larger peak powers, of the order of a gigawatt, can be expected for UV radiation with lambda in the range of 500-2000 AA. The authors discuss the physical principles of these systems and give examples of how they might be built. (14 References).
keywords:
Download | Details | Edit | Delete
title: Quasi-isochronous storage ring
format: journal article
publisher: Nuclear Instruments & Methods A
year: 1991
2 authors: C. Pellegrini | D. Robin
abstract: The authors study the single particle and collective dynamics of a storage ring where the momentum compaction is made small to make it nearly isochronous, to reduce the bunch length and increase the peak current. They find that a quasi-isochronous ring makes it possible to obtain a bunch length in the millimeter range and to increase the beam longitudinal brilliance by more than one order of magnitude. (16 References).
keywords:
Download | Details | Edit | Delete
title: Transverse Equilibria in Linear Collider Beam-Beam Collisions
format: journal article
publisher: Physical Review E
year: 1991
2 authors: J.B. Rosenzweig | P. Chen
abstract:
keywords:
Download | Details | Edit | Delete
title: Crossing of an incoherent integral resonance in the electron ring accelerator
format: journal article
publisher: Nuclear Instruments & Methods
year: 1970
2 authors: C. Pellegrini | A. M. Sessler
abstract: In one mode of operation of an electron ring accelerator (ERA), at the end of compression rings are slowly moved through the radial integral betatron resonance Q_r=1. Although the coherent radial oscillation frequency of the ring as a whole remains below unity, the oscillation frequencies of individual electron are (incoherently) caused to pass through the resonance because of the additional focusing from ions trapped in the ring. In this paper the effect of field errors on ring major and minor radii is evaluated-theoretically-for the cases in which the spread in the square of the electron oscillation frequency ( Delta(2)) is (a) much smaller and (b) much larger than the contribution to the square of the oscillation frequency from the ions ( Lambda(2)).
keywords:
Download | Details | Edit | Delete
title: Coherent Transition Radiation Dignosis of Microbunching at the Exit of a Free-Electron Laser Undulator
format: journal article
publisher: Nuclear Instruments and Methods in Physics Research
year: March 6, 1995
3 authors: J.B. Rosenzweig | G. Travish | A. Tremaine
abstract: The action of the free-electron laser instability (FEL) on an electron beam produces a longitudinal density modulation with a periodicity near the resonant radiation wavelength. This modulation, which can produce femtosecond or shorter microbunches inside of a macroscopic picosecond electron pulse, has been proposed for use as a prebunching injector for both higher harmonic FELs and short wavelength accelerators. Standard methods involving streak cameras or beam sweeping with dipole mode cavities will certainly fail to provide information about this longitudinal microstructure, however. In this paper we explore the use of coherent transition radiation generated from a foil a the exit of an FEL undulator to diagnose both the lognitudinal and transverse electron microbunch structure.
keywords:
Download | Details | Edit | Delete
title: Comparison of the coherent radiation-induced microbunching instability in a free-electron laser and a magnetic chicane
format: journal article
publisher: Physical Review Special Topics-Accelerators & Beams
year: 2003
2 authors: Sven Reiche | J.B. Rosenzweig
abstract: A self-amplified spontaneous emission free-electron laser (SASE FEL) is a device which is based on the creation of a very intense, relativistic electron beam which has very little temperature in all three phase planes. The beam in this system is described as having "high brightness,'' and when it is bent repetitively in a magnetic undulator, undergoes a radiation-mediated microbunching instability. This instability can amplify the original radiation amplitude at a particular, resonant wavelength by many orders of magnitude. In order to obtain high brightness beams, it is necessary to compress them to obtain higher currents than available from the electron source. Compression is accomplished by the use of magnetic chicanes, which are quite similar to, if much longer than, a single period of the undulator. It should not be surprising that such chicanes also support a radiation-mediated microbunching interaction, which has recently been investigated, and has been termed coherent synchrotron radiation (CSR) instability. The purpose of this paper is to compare and contrast the characteristics of the closely related FEL and CSR microbunching instabilities. We show that a high-gain regime of the CSR instability exists which is formally similar to the FEL instability.
keywords:
Download | Details | Edit | Delete
title: Experimental confirmation of transverse focusing and adiabatic damping in a standing wave linear accelerator
format: journal article
publisher: Physical Review E
year: 1997
10 authors: Sven Reiche | J.B. Rosenzweig | S. Anderson | Pedro Frigola | M. Hogan | A. Murokh | C. Pellegrini | L. Serafini | G. Travish | A. Tremaine
abstract: The measurement of the transverse phase-space map, or transport matrix, of a relativistic electron in a high-gradient, radio-frequency linear accelerator (rf linac) at the UCLA photoinjector is reported. This matrix, which indicates the effects of acceleration (adiabatic damping), first-order transient focusing, and ponderomotive second-order focusing, is measured as a function of both rf field amplitude and phase in the linac. The elements of the matrix, determined by observation of centroid motion at a set of downstream diagnostics due to deflections induced by a set of upstream steering magnets, compare well with previously developed analytical theory [J. Rosenzweig and L. Serafini, Phys. Rev. E 49, 1599 (1994)]. The determinant of the matrix is obtained, yielding a direct confirmation of trace space adiabatic damping. Implications of these results on beam optics at moderate energy in high-gradient linear accelerators such as rf photoinjectors are discussed.
keywords:
Download | Details | Edit | Delete
title: Quasi-isochronous storage rings
format: journal article
publisher: Physical Review E
year: 1993
4 authors: D. Robin | E. Forest | C. Pellegrini | A. Amiry
abstract: A study is made of the single-particle dynamics of an electron-positron storage ring where the phase-slip factor is made small in order to make the ring nearly isochronous and reduce the bunch length. What is found is that a quasi-isochronous ring makes it possible to obtain a bunch length in the millimeter range, about one order of magnitude shorter than present values. In this study the authors have extended the work of others on isochronous storage rings by quantitatively including higher-order terms in the longitudinal equations of motion. Scaling laws are then derived relating the linear term with the next-highest-order term. These scaling laws, which are derived from a two-dimensional Hamiltonian (one dimension of position and one of momentum), establish criteria for stability. These scaling laws are then checked with full six-dimensional tracking on one particular lattice. (13 References).
keywords:
Download | Details | Edit | Delete
title: A proposed dielectric-loaded resonant laser accelerator
format: journal article
publisher: Physical Review Letters
year: 1995
3 authors: J.B. Rosenzweig | A. Murokh | C. Pellegrini
abstract: A laser-pumped accelerator utilizing a resonant, periodic, dielectric structure is proposed. The electromagnetic fields due to a side-injected laser beam impinging on this structure are calculated in a two-dimensional standing-wave approximation, leading to an estimated accelerating field in excess of 1 GV/m for accessible experimental parameters. The longitudinal dynamics of injected electrons in the device are discussed, as are the first- and second-order transverse focusing effects inherent to this structure. Similarities and differences between this scheme and conventional and other advanced accelerators are examined. (15 References).
keywords:
Download | Details | Edit | Delete
title: Coherent transition radiation diagnosis of electron beam microbunching
format: journal article
publisher: Nuclear Instruments & Methods A
year: 1995
3 authors: J.B. Rosenzweig | G. Travish | A. Tremaine
abstract: The action of the free-electron laser instability (FEL) on an electron beam produces a longitudinal density modulation with a periodicity near the resonant radiation wavelength. This modulation, which can produce femtosecond or shorter microbunches inside of a macroscopic picosecond electron pulse, has been proposed for use as a prebunching injector for both higher harmonic FELs and short wavelength accelerators. Standard methods involving streak cameras or beam sweeping with dipole mode cavities will certainly fail to provide information about this longitudinal microstructure, however. In this paper we explore the use of coherent transition radiation generated from a foil at the exit of an FEL undulator to diagnose both the longitudinal and transverse electron microbunch structure. (12 References).
keywords:
Download | Details | Edit | Delete
title: Isochronous storage-rings and high-luminosity electron-positron colliders
format: journal article
publisher: Annals of the NY Academy of Sciences
year: 1991
2 authors: C. Pellegrini | D. Robin
abstract:
keywords:
Download | Details | Edit | Delete
title: Nonlinear Plasma Dynamics in the Plasma Wakefield Accelerator
format: journal article
publisher: IEEE Transactions on Plasma Science
year: 1987
1 author: J.B. Rosenzweig
abstract: Excitation of nonlinear plasma oscillations by an intense ultrarelativistic electron beam is considered. It is shown, by analytical solutions of the one-dimensional relativistic fluid equations, that under certain conditions on the relative electron-beam and plasma densities extremely large longitudinal electric fields can be generated in the beam's wake. This scheme is a nonlinear version of the plasma wake-field accelerator, and is predicted to have advantages over the linear regime.
keywords:
Download | Details | Edit | Delete
title: Study of magnetic lattice for a quasi-isochronous ring
format: journal article
publisher: Particle Accelerators
year: 1994
4 authors: A. Amiry | C. Pellegrini | E. Forest | D. Robin
abstract: Quasi-isochronous rings (QIRs) have been considered for electron-positron colliders to obtain large luminosity with a small average beam current. This approach offers the advantage of minimizing vacuum and RF system problems, and multibunch instability effects. In this paper, we review the basic physics of a QIR, the condition for stable single-particle motion, and the dynamic aperture. The collider we discuss is a Phi( Phi ) factory with a single ring and beam energy of 510 MeV. This ring uses a very strong focusing of the electron and positron beams at the interaction point, i.e., a beta function in the millimeter range; and a momentum compaction variable over a large range, of -0.008 to +0.005, to control the bunch length. It has a luminosity of 10(33) cm(-2) s(-1), average current smaller than 1 A, and a perimeter of 32.7 meter. Its transverse chromaticities and second-order momentum compaction are set to zero by utilizing three families of the sextupoles. The QIR dynamic aperture is calculated using a new computer code, KRAKPOT, written explicitly for small rings.
keywords:
Download | Details | Edit | Delete
title: First Observation of Self-Amplified Spontaneous Emission in a Free-Electron Laser at 109 nm Wavelength
format: journal article
publisher: Physical Review Letters
year: 2000
145 authors: J. Andruszkow | B. Aune | V. Ayvazyan | N. Baboi | R. Bakker | V. Balakin | D. Barni | A. Bazhan | M. Bernard | A. Bosotti | J. C. Bourdon | W. Brefeld | R. Brinkmann | S. Buhler | J. P. Carneiro | M. Castellano | P. Castro | L. Catani | S. Chel | Y. Cho | S. Choroba | E. R. Colby | W. Decking | P. Den Hartog | M. Desmons | M. Dohlus | D. Edwards | H. T. Edwards | B. Faatz | J. Feldhaus | M. Ferrario | M. J. Fitch | K. Floettman | M. Fouaidy | A. Gamp | T. Garvey | C. Gerth | M. Geitz | E. Gluskin | V. Gretchko | U. Hahn | W. H. Hartung | D. Hubert | M. Huening | R. Ischebek | M. Jablonka | J. M. Joly | M. Juillard | T. Junquera | P. Jurkiewicz | A. Kabel | J. Kahl | H. Kaiser | T. Kamps | V. V. Katelev | J. L. Kirchgessner | M. Koerfer | L. Kravchuk | G. Kreps | J. Krzywinski | T. Lokajczyk | R. Lange | B. Leblond | M. Leenen | J. Lesrel | M. Liepe | A. Liero | T. Limberg | R. Lorenz | H. H. Lu | F. H. Lu | C.4 Magne | M. Maslov | G. Materlik | A. Matheisen | J. Menzel | P. Michelato | W. D. Moeller | A. Mosnier | U. C. Mueller | O. Napoly | A. Novokhatski | M. Omeich | H. S. Padamsee | C. Pagani | F. Peters | B. Petersen | P. Pierini | J. Pflueger | P. Piot | B. Phung Ngoc | L. Plucinski | D. Proch | K. Rehlich | Sven Reiche | D. Reschke | I. Reyzl | J.B. Rosenzweig | J. Rossbach | S. Roth | E. L. Saldin | W. Sandner | Z. Sanok | H. Schlarb | G. Schmidt | P. Schmueser | J. R. Schneider | E. A. Schneidmiller | H. J. Schreiber | S. Schreiber | P. Schuett | J. Sekutowicz | L. Serafini | D. Sertore | S. Setzer | S. Simrock | B. Sonntag | B. Sparr | F. Stephan | V. A. Sytchev | S. Tazzari | F. Tazzioli | M. Tigner | M. Timm | M. Tonutti | E. Trakhtenberg | R. Treusch | D. Trines | V. Verzilov | T. Vielitz | V. Vogel | G. v. Walter | R. Wanzenberg | T. Weiland | H. Weise | J. Weisend | M. Wendt | M. Werner | M. M. White | I. Will | S. Wolff | M. V. Yurkov | K. Zapfe | P. Zhogolev | F. Zhou
abstract: We present the first observation of self-amplified spontaneous emission (SASE) in a free-electron laser (FEL) in the vacuum ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approximately 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width, and intensity fluctuations, are all consistent with the present models for SASE FELs.
keywords:
Download | Details | Edit | Delete
title: Feasibility study of a storage ring for a high-power XUV free-electron laser
format: journal article
publisher: Particle Accelerators
year: 1986
12 authors: J. Bisognano | S. Chattopadhyay | M. Cornacchia | A. Garren | K. Halbach | A. Jackson | K. J. Kim | H. Lancaster | J. Peterson | M. Zisman | C. Pellegrini | G. Vignola
abstract: A high-gain free-electron lase (FEL), operating in a special by-pass of a storage ring, can provide tens of megawatts of coherent power at wavelengths shorter than 1000 AA. The requirements on beam quality 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 about 10/sup -3/. Designing an electron storage ring with the required characteristics involves a comprehensive analysis of the restrictions arising 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. (39 References).
keywords:
Download | Details | Edit | Delete
title: Collective instabilities and high-gain regime in a free electron laser
format: journal article
publisher: Optics Communications
year: 1984
3 authors: R. Bonifacio | C. Pellegrini | L. M. Narducci
abstract: The authors study the behavior of a free electron laser in the high gain regime, and the conditions for the emergence of a collective instability in the electron beam-undulator-field system. The authors' equations, in the appropriate limit, yield the traditional small gain formula. In the nonlinear regime, numerical solutions of the coupled equations of motion support the correctness of their proposed empirical estimator for the build-up time of the pulses, and indicate the existence of optimum parameters for the production of high peak-power radiation. (11 References).
keywords:
Download | Details | Edit | Delete
title: The classical theory of the transverse optical klystron for a nonmonoenergetic beam
format: journal article
publisher: Journal of Applied Physics
year: 1985
6 authors: I. Boscolo | M. Leo | R. A. Leo | G. Soliani | V. Stagno | C. Pellegrini
abstract: In this paper the classical theory of the transverse optical klystron is presented. The gain is obtained by solving analytically the Vlasov equation which governs the evolution of the electron beam along the undulator magnet. The initial energy distribution of the electron beam is assumed gaussian. Both the small signal and the saturation regime are investigated. (19 References).
keywords:
Download | Details | Edit | Delete
title: Visible-infrared self-amplified spontaneous emission amplifier free electron laser undulator
format: journal article
publisher: Physical Review Special Topics-Accelerators & Beams
year: 2001
17 authors: R. Carr | M. Cornacchia | P. Emma | H. D. Nuhn | B. Poling | R. Ruland | E. Johnson | G. Rakowsky | J. Skaritka | S. Lidia | P. Duffy | M. Libkind | Pedro Frigola | A. Murokh | C. Pellegrini | J.B. Rosenzweig | A. Tremaine
abstract: The visible-infrared self-amplified spontaneous emission amplifier (VISA) free electron laser (FEL) is an experimental device designed to show self-amplified spontaneous emission (SASE) to saturation in the near infrared to visible light energy range. It generates a resonant wavelength output from 800?600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is designed to show how SASE FEL theory corresponds with experiment in this wavelength range, using an electron beam with emittance close to that planned for the future Linear Coherent Light Source at SLAC. VISA comprises a 4 m pure permanent magnet undulator with four 99 cm segments, each of 55 periods, 18 mm long. The undulator has distributed focusing built into it, to reduce the average beta function of the 70?85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walk-off, or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, we were able to control trajectory walk-off to less than
keywords:
Download | Details | Edit | Delete
title: Proposed continuous wave energy recovery operation of an x-ray free electron laser
format: journal article
publisher: Physical Review Special Topics - Accelerators and Beams
year: 2005
17 authors: J. Sekutowicz | S.A. Bogacz | D. Douglas | P. Kneisel | G.P. Williams | M. Ferrario | I. Ben-Zvi | J. Rose | J. Smedley | Srinivasan-Rao, T. | L. Serafini | W.D. Moller | B. .Petersen | D. Proch | S. Simrock | P. Colestock | J.B. Rosenzweig
abstract: Commissioning of two large coherent light facilities (XFELs) at SLAC and DESY should begin in 2008 and 2011, respectively. In this paper we look further into the future, hoping to answer, in a very preliminary way, two questions. First: What will the next generation of XFEL facilities look like? Believing that superconducting technology offers advantages such as high quality beams with highly populated bunches, the possibility of energy recovery and higher overall efficiency than warm technology, we focus this preliminary study on the superconducting option. From this belief the second question arises: What modifications in superconducting technology and in the machine design are needed, as compared to the present DESY XFEL, and what kind of research and development program should be proposed to arrive in the next few years at a technically feasible solution with even higher brilliance and increased overall conversion of ac power to photon beam power? In this paper we will very often refer to and profit from the DESY XFEL design, acknowledging its many technically innovative solutions.
keywords:
Download | Details | Edit | Delete
title: First observation of luminosity-driven extraction using channeling with a bent crystal
format: journal article
publisher: Physical Review Special Topics-Accelerators & Beams
year: 1998
26 authors: R. Carrigan | D. Chen | G. Jackson | N. Mokhov | C.T. Murphy | S. I. Baker | S. A. Bogacz | D. B. Cline | S. Ramachandran | J. Rhoades | J.B. Rosenzweig | A. Asseev | R. A. Biryukov | A. Taratin | J. A. Ellison | A. Khanzadeev | T. Prokofieva | V. Samsonov | G. Solodov | B. Newberger | E. Tsyganov | H. J. Shih | W. Gabella | B. Cox | V. Golovatyuk | A. McManus
abstract: Luminosity-driven channeling extraction has been observed for the first time using a 900 GeV circulating proton beam at the superconducting Fermilab Tevatron. The extraction efficiency was found to be about 30%. A 150 kHz beam was obtained during luminosity-driven extraction with a tolerable background rate at the collider experiments. A 900 kHz beam was obtained when the background limits were doubled. This is the highest energy at which channeling has been observed.
keywords:
Download | Details | Edit | Delete
title: Creation of plasma density transitions short compared to the plasma skin-depth
format: journal article
publisher: REVIEW OF SCIENTIFIC INSTRUMENTS
year: 2005
3 authors: M.C. Thompson | J.B. Rosenzweig | G. Travish
abstract: A plasma based electron beam source apparatus is described which creates a plasma with two distinct density regions separated by a transition which is shorter than the plasma skin depth kp^−1 of either region. This sharp density modulation is achieved by using a perforated stainless steel screen to filter half of a diffusing plasma column. A simple physical model predicts that the length of the plasma density transition will vary with the distance from the screen. For a weakly magnetized plasma, the transition length will be twice the distance, on a line normal to the screen plane, from the screen edge to the location where the transition is measured. The plasma column is generated using an argon discharge plasma source. It has a peak density of approximately 3.53 X 10^13 cm^−3 and a full width half maximum width of 5 cm. The discharge source utilizes a 7.5 cm diameter LaB6 disk cathode heated to 1300
keywords:
Download | Details | Edit | Delete
title: Beam extraction studies at 900 GeV using a channeling crystal
format: journal article
publisher: Physical Review Special Topics-Accelerators & Beams
year: 2002
26 authors: R. Carrigan | D. Chen | G. Jackson | N. Mokhov | C.T. Murphy | S. I. Baker | S. A. Bogacz | D. B. Cline | S. Ramachandran | J. Rhoades | J.B. Rosenzweig | A. Asseev | R. A. Biryukov | A. Taratin | J. A. Ellison | A. Khanzadeev | T. Prokofieva | V. Samsonov | G. Solodov | B. Newberger | E. Tsyganov | H. J. Shih | W. Gabella | B. Cox | V. Golovatyuk | A. McManus
abstract: Luminosity-driven channeling extraction has been observed for the first time in a 900 GeV study at the Fermilab Tevatron. This experiment, Fermilab E853, demonstrated that useful TeV level beams can be extracted from a superconducting accelerator during high luminosity collider operations without unduly affecting the background at the collider detectors. Multipass extraction was found to increase the efficiency of the process significantly. The beam extraction efficiency was about 25%. Studies of time dependent effects found that the turn-to-turn structure was governed mainly by accelerator beam dynamics. Based on the results of this experiment, it is feasible to construct a parasitic 5?10 MHz proton beam from the Tevatron collider.
keywords:
Download | Details | Edit | Delete
title: Velocity bunching of high-brightness electron beams
format: journal article
publisher: Physical Review Special Topics - Accelerators and Beams
year: 2005
11 authors: S. Anderson | P. Musumeci | J.B. Rosenzweig | W. J. Brown | R. J. England | M. Ferrario | J. S. Jacob | M.C. Thompson | G. Travish | A.M. Tremaine | R. Yoder
abstract: Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modernhigh brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS) experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly in ICS experiments, are presented.
keywords:
Download | Details | Edit | Delete
title: Extraction from TeV-Range Accelerators Using Bent Crystal Channeling
format: journal article
publisher: Nuclear Instruments & Methods B
year: 1994
45 authors: R.A. Carrigan | D. Chen | P. Colestock | D. Herrup | G. Goderre | G. Jackson | C.T. Murphy | R. Stefanski | S. Baker | N. Mokhov | B. Parker | H. J. Shih | R. Soundranayagam | T. Toohig | S. Peggs | C. R. Sun | A. Boden | D. B. Cline | W. Gabella | S. Ramachandran | J. Rhoades | J.B. Rosenzweig | M. Arenton | S. Conetti | B. Cox | D. Dukes | V. Golovatyuk | A. McManus | K. Nelson | B. Norem | B. Newberger | J. A. Ellison | A. Erwin | R. Rossmanith | A. Kovalenko | A. Taratin | N. Malakhov | E. Tsyganov | M. Bavizhev | V. Biryukov | M. Maslov | A. Khanzadeev | T. Prokofieva | V. Samsonov | G. Solodov
abstract: Plans and first results from Fermilab Experiment 853 are presented. E853 is an experiment to test the feasibility and efficiency of extracting a low-intensity beam from the halo of the Tevatron using channeling in a bent silicon crystal. The motivation of the experiment is to apply crystal extraction to trans-TeV accelerators like the LHC. Channeling developments related to crystal extraction and some early results from accelerator studies at the Tevatron are presented.
keywords:
Download | Details | Edit | Delete
title: Sextupole Correction of the Longitudinal Transport of Relativistic Beams in Dispersionless Translating Sections
format: journal article
publisher: Physical Review Special Topics: Accelerators and Beams
year:
6 authors: R. J. England | J.B. Rosenzweig | G. Andonian | P. Musumeci | G. Travish | R. Yoder
abstract: We examine the use of sextupole magnets to correct nonlinearities in the longitudinal phase space transformation of a relativistic beam of charged particles in a dispersionless translating section, or dogleg. Through heuristic analytical arguments and examples derived from recent experimental endeavors and augmented by simulations using the particle tracking codes PARMELA and ELEGANT, sextupole corrections are found to be potentially useful in facilitating the use of such structures for beam compression or for shaping the current profile of the beam, by manipulation of the second-order longitudinal dispersion (or T566). Recent experimental evidence of the use of sextupoles to manipulate second-order horizontal and longitudinal dispersion of the beam is presented. The theoretical and experimental results indicate that these manipulations could be used to create an electron bunch with a current profile having a long ramp followed by a sharp cut-off, which is optimal for driving large amplitude wake fields in a plasma wake field accelerator.
keywords:
Download | Details | Edit | Delete
title: Final focusing and enhanced disruption from an underdense plasma lens in a linear collider
format: journal article
publisher: Physical Review D
year: 1989
3 authors: P. Chen | Rajagopalan, S. | J.B. Rosenzweig
abstract: In this work we examine the viability of employing an underdense plasma lens as a final focusing method for a linear e+e- collider. The underdense plasma lens is superior to the overdense lens in that it improves focusing linearity and background event rate, but works well only for electrons. We thus consider the interaction of an e- beam which is smaller than the e+ beam at collision, a case we term "bootstrap disruption." The potential luminosity enhancement is determined by analysis of the lens optics and simulation of the bootstrap disruption.
keywords:
Download | Details | Edit | Delete
title: Development of X-ray Free-electron Lasers
format: journal article
publisher: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS,
year: 2004
2 authors: C. Pellegrini | Sven Reiche
abstract: We review and discuss the theoretical and experimental work that has led to the development of short wavelength free-electron lasers operating as single pass amplifiers, starting from the spontaneous undulator radiation, in the self amplified spontaneous emission mode. This work has led to several projects to build this type of free-electron lasers operating at a wavelength of about 0.1 nm, producing coherent X-ray pulses with an unprecedented brilliance and peak power, and pulse length in the femtosecond range. One such project, the LCLS, is presently under construction and is expected to be operational in 2008.
keywords:
Download | Details | Edit | Delete
title: A high-luminosity BB factory linear collider using positron recirculation and recovery
format: journal article
publisher: Nuclear Instruments & Methods A
year: 1990
2 authors: D. B. Cline | C. Pellegrini
abstract: The authors describe an asymmetric linear collider BB factory scheme that offers a possible solution to most of the problems encountered in the design of BB factories to operate at the Upsilon (4S) energy. A key feature of this collider is the recirculation and recovery of the positrons and the asymmetric energy of the collider to better achieve the search for CP violation in the B system. (8 References).
keywords:
Download | Details | Edit | Delete
title: Observation of Anomalously Large Spectral Bandwidth in a High-Gain Self-Amplified Spontaneous Emission Free Elctron Laser
format: journal article
publisher: Physical Review Letters
year: 2005
14 authors: G. Andonian | A. Murokh | J.B. Rosenzweig | R. Agustsson | M. BABZIEN | I. Ben-Zvi | P. Frigola | J.Y. Huang | L. Palumbo | C. Pellegrini | Sven Reiche | G. Travish | C. Vicario | V. Yakimenko
abstract: Observation of ultrawide bandwidth, up to 15% full-width, high-gain operation of a self-amplified spontaneous emission free-election laser (SASE FEL) is reported. This type of lasing is obtained with a strongly chirped beam (E=E  1:7%) emitted from the accelerator. Because of nonlinear pulse compression during transport, a short, high current bunch with strong mismatch errors is injected into the undulator, giving high FEL gain. Start-to-end simulations reproduce key features of the measurements and provide insight into mechanisms, such as angular spread in emitted photon and electron trajectory distributions, which yield novel features in the radiation spectrum.
keywords:
Download | Details | Edit | Delete
title: High-energy inverse free-electron-laser accelerator
format: journal article
publisher: Physical Review A
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 analyzed, and the effect of synchrotron-radiation losses is studied. The longitudinal phase stability of accelerated particles is also analyzed. 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 the acceleration process. (22 References).
keywords:
Download | Details | Edit | Delete
title: Higher harmonic inverse free-electron laser interaction
format: journal article
publisher: Physical Review E
year: 2005
3 authors: P. Musumeci | C. Pellegrini | J.B. Rosenzweig
abstract: We expand the theory of the inverse free electron laser IFEL interaction to include the possibility of energy exchange that takes place when relativistic particles traversing an undulator interact with an electromagnetic wave of a frequency that is a harmonic of the fundamental wiggler resonant frequency. We derive the coupling coefficients as a function of the IFEL parameters for all harmonics, both odd and even. The theory is supported by simulation results obtained with a three-dimensional Lorentz equation solver code. Comparisons are made between the results of theory and simulations, and the recent UCLA IFEL experimental results where higher harmonic IFEL interaction was observed.
keywords:
Download | Details | Edit | Delete
title: Plasma electron fluid motion and wave breaking near a density transition
format: journal article
publisher: Physical Review E
year: 2002
3 authors: R. J. England | J.B. Rosenzweig | N. Barov
abstract: Recently, Suk, Barov, and Rosenzweig [Phys. Rev. Lett. 86, 1011 (2001)] proposed a scheme for trapping background electrons in a plasma wake field using a sudden downward transition in the background ion density, where the density transition length is small compared to the plasma skin depth. In the present paper we present a fluid dynamical description of this mechanism that is self-consistent up to the point of wave breaking. A one-dimensional nonlinear relativistic second-order differential equation is derived for the electron fluid velocity in Lagrangian coordinates. Numerical integrations of this equation are used to map out the regions of parameter space in which wave breaking occurs and to determine the extent of the downstream region of plasma involved in wave breaking. Comparisons with one-dimensional particle-in-cell (PIC) simulations show that the onset of trapping occurs at the parameter values where wave breaking begins in the fluid analysis, but that the downstream extent of plasma involved in wave breaking is not a reliable predictor of the number of trapped particles. The PIC simulations also reveal that particles initially located on the upstream side of the density transition may become trapped, although these particles do not participate in wave breaking in the fluid description.
keywords:
Download | Details | Edit | Delete
title: Effects of Ion Motion in Intense Beam-Driven Plasma Wakefield Accelerators
format: journal article
publisher: Physical Review Letters
year: 2005
5 authors: J.B. Rosenzweig | A.M. Cook | A. Scott | M.C. Thompson | R. B. Yoder
abstract: Recent proposals for using plasma wakefield accelerators (PWFA) as a component of a linear collider have included intense electron beams with densities many times in excess of the plasma density. The beams electric fields expel the plasma electrons from the beam path to many beam radii in this regime. We analyze here the motion of plasma ions under the beam fields, and find for a proposed PWFA collider scenario that the ions completely collapse inside of the beam. Simulations of ion collapse are presented. Implications of ion motion on the feasibility of the PWFA-based colliders are discussed.
keywords:
Download | Details | Edit | Delete
title: Side-coupled slab-symmetric structure for high-gradient acceleration using terahertz power
format: journal article
publisher: Physical Review Special Topics - Accelerators and Beams
year: 2005
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 described. The device is resonantly excited by an external drive laser which is side coupled into the acceleration region; a novel coupling scheme, which consists of an array of narrow, equally spaced slots in the upper structure boundary, is presented and analyzed in detail. This structure partakes of the advantages of earlier slab-symmetric optical acceleration proposals, but will use a terahertz-frequency external radiation source ( 340 m), allowing realistic electron beams to be used in a proof-of-principle experiment. Two- and three-dimensional electromagnetic simulations are used to verify the mode patterns and study the effects of the couplers, including time-dependent calculations of the filling of the structure and particle-in-cell computations of the beam wakefields. Details of the resonance are found to be highly sensitive to the coupling slot geometry: the presence of the couplers can lead to frequency detuning, changes in the field breakdown limits and overall Q factor, and distortions of the field pattern. Beam wakefields are enhanced by the presence of the slots, but found to have no significant effect on the beam transport. The resonant accelerating fields, which are nearly constant along the short transverse direction, are found to have between 10 and 15 times the amplitude of the driving radiation, with only a small ( < 10%) admixture of other nonaccelerating modes. Field gradients are computed to be near 100 MV=m when the structure is driven with 100MWof terahertz laser power. Possible manufacturing methods for a prototype device are discussed.
keywords:
Download | Details | Edit | Delete
title: Pulsed-laser nonlinear Thomson scattering for general scattering geometries
format: journal article
publisher: Physical Review E
year: 23 November 2005
3 authors: G. A. Krafft | A. Doyuran | J.B. Rosenzweig
abstract: In a recent paper it has been shown that single electron Thomson backscatter calculations can be performed including the effects of pulsed high intensity lasers. In this paper we present a more detailed treatment of the problem and present results for more general scattering geometries. In particular, we present new results for 90 Thomson scattering. Such geometries have been increasingly studied as x-ray sources of short-pulse radiation. Also, we present a clearer physical basis for these different cases.
keywords:
Download | Details | Edit | Delete
title: Emittance compensation with dynamically optimized photoelectron beam profiles
format: journal article
publisher: Nuclear Instruments and Methods in Physics Research A
year: 2005
4 authors: J.B. Rosenzweig | A.M. Cook | M. Dunning | M. Ferrario
abstract: Much of the theory and experimentation concerning creation of a high-brightness electron beam from a photocathode, and then applying emittance compensation techniques, assumes that one must strive for a uniform density electron beam, having a cylindrical shape. On the other hand, this shape has large nonlinearities in the space-charge field profiles near the beam
keywords:
Download | Details | Edit | Delete
title: Optimization and beam dynamics of a superconducting radio-frequency gu
format: journal article
publisher: Nuclear Instruments and Methods in Physics Research A
year:
5 authors: M. Ferrario | W. D. Moeller | J.B. Rosenzweig | J. Sekutowicz | G. Travish
abstract: Recent advances in superconducting radio-frequency (RF) technology and a better understanding of RF photoinjector design optimization make it possible to propose a specific design for a superconducting RF gun that can simultaneously produce both ultra-high peak brightness and high average current. Such a device is a critical component of next generation X-ray sources, such as self-amplified spontaneous emission free-electron lasers (SASE FEL) and energy recovery linac-based systems. The design presented in this paper is scaled from the present state-of-the-art normal conducting RF photoinjector that has been studied in the context of the linac coherent light source and SPARC SASE FEL injection schemes. Issues specific to the superconducing RF photoinjector, such as accelerating gradient limit, RF cavity and cryostat design, and compatibility with magnetic focusing and laser excitation of a photocathode are discussed.
keywords:
Download | Details | Edit | Delete
title: Strong sextupole focusing in planar undulators
format: journal article
publisher: Nuclear Instruments & Methods A
year: 1994
2 authors: G. Travish | J.B. Rosenzweig
abstract: The range of parameters used in both working and proposed free electron lasers (FELs) has greatly expanded in recent years. Future machines are envisioned as fourth generation light sources providing researchers with high brightness, short wavelength, coherent radiation [see Ref. [1]: Report on the Workshop on Fourth Generation Light Source SLAC, Stanford CA, USA (February, 1992)] . Short wavelength operation, along with the long undulator required to produce high brightness photon beams in these devices, 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 . The equations of motion for an electron in an undulator field with a strong sextupole component are examined . Analytic as well as smooth approximation solutions are provided for AG sextupole focusing . It is shown that the mean electron longitudinal velocity can be kept constant through each focusing and defocusing section, but that the velocity differs between these sections . The effects of this stepwise velocity modulation as well as the beam size variation are explored computationally and compared to theory. Examples using the proposed SLAC 4 nm FEL, the UCLA 10.6 wm FEL as well as a Paladin based device are also given.
keywords:
Download | Details | Edit | Delete
title: Short-pulse, high-brightness X-ray production with the PLEIADES Thomson-scattering source
format: journal article
publisher: Applied Physics B
year: 2004
1 author: S. Anderson
abstract: PLEIADES is a compact, tunable, high-brightness, ultra-short-pulse, Thomson-scattering X-ray source. Picosecond pulses of hard X-rays (10
keywords:
Download | Details | Edit | Delete
title: Measurements of High Gain and Intensity Fluctuations in a Self-Amplified, Spontaneous-Emission Free-Electron Laser
format: journal article
publisher: Physical Review Letters
year: 1998
12 authors: M. Hogan | C. Pellegrini | J.B. Rosenzweig | G. Travish | A. A. Varfolomeev | S. Anderson | K. Bishofberger | Pedro Frigola | A. Murokh | N. Osmanov | Sven Reiche | A. Tremaine
abstract: We report measurements of large gain for a single pass free-electron laser operating in self-amplified spontaneous emission (SASE) at 16 mm 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.
keywords:
Download | Details | Edit | Delete
title: Self-amplified spontaneous emission saturation at the Advanced Photon Source free-electron laser
format: journal article
publisher: Review of Scientific Instruments
year: 2002
29 authors: E. R. Moog | S. V. Milton | N. D. Arnold | C. Benson | W. Berg | S. G. Biedron | M. Borland | Y. C. Chae | R. J. Dejus | P. K. Den Hartog | B. Deriy | M. Erdmann | E. Gluskin | Z. Huang | K. J. Kim | J. W. Lewellen | Y. Li | A. H. Lumpkin | O. Makarov | A. Nassiri | V. Sajaev | R. Soliday | B. J. Tieman | E. M. Trakhtenberg | G. Travish | I. B. Vasserman | N. A. Vinokurov | G. Wiemerslage | B. X. Yang
abstract: Today, many bright photon beams in the ultraviolet and x-ray wavelength range are produced by insertion devices installed in specially designed third-generation storage rings. There is the possibility of producing photon beams that are orders of magnitude brighter than presently achieved at synchrotron sources, by using self-amplified spontaneous emission (SASE). At the Advanced Photon Source (APS), the low-energy undulator test line (LEUTL) free-electron laser (FEL) project was built to explore the SASE process in the visible through vacuum ultraviolet wavelength range. While the understanding gained in these experiments will guide future work to extend SASE FELs to shorter wavelengths, the APS FEL itself will become a continuously tunable, bright light source. Measurements of the SASE process to saturation have been made at 530 and 385 nm. A number of quantities were measured to confirm our understanding of the SASE process and to verify that saturation was reached. The intensity of the FEL light was measured versus distance along the FEL, and was found to flatten out at saturation. The statistical variation of the light intensity was found to be wide in the exponential gain region where the intensity is expected to be noisy, and narrower once saturation was reached. Absolute power measurements compare well with GINGER simulations. The FEL light spectrum at different distances along the undulator line was measured with a high-resolution spectrometer, and the many sharp spectral spikes at the beginning of the SASE process coalesce into a single peak at saturation. The energy spread in the electron beam widens markedly after saturation due to the number of electrons that transfer a significant amount of energy to the photon beam. Coherent transition radiation measurements of the electron beam as it strikes a foil provide additional confirmation of the microbunching of the electron beam. The quantities measured confirm that saturation was indeed reached. Details are given in Milton et al., Science 292, 2037 (2001) (also online at www.sciencexpress.org as 10.1126/science. 1059955, 17 May 2001), and Lewellen et al., "Present Status and Recent Results from the APS SASE FEL," to be published in the Proceedings of the 23rd International Free-Electron Laser Conference, Darmstadt, Germany, 20?24 August 2001.
keywords:
Download | Details | Edit | Delete
title: Collective Instability of a Free-Electron Laser Including Space-Charge and Harmonics
format: journal article
publisher: Optics Communications
year: 1985
3 authors: J.B. Murphy | C. Pellegrini | R. Bonifacio
abstract: The effects of harmonics, space charge and electron energy spread on the collective instability regime of an electron beam coupled to a planar undulator are analyzed. Both analytical and numerical results are presented.
keywords:
Download | Details | Edit | Delete
title: Transverse particle motion in radio-frequency linear accelerators
format: journal article
publisher: Physical Review E
year: 1994
2 authors: J.B. Rosenzweig | L. Serafini
abstract: The transverse motion of a relativistic charged particle in a radio-frequency linear accelerator (rf linac) is examined. The spatially averaged equations of motion are derived for a particle in a periodic accelerating cavity system, and solved exactly in the ultrarelativistic limit. These solutions, along with an impulse treatment of the transients at the entrance and exit of the linac cavities, allow derivation of a linear transport matrix through the cavity. This generalized matrix is improved over previously derived results in that it is applicable to both traveling- and standing-wave structures, allows for arbitrary injection phase and spatial-harmonic content of the rf fields, and is more accurate in approximating the exact charged-particle motion.
keywords:
Download | Details | Edit | Delete
title: Experimental measurement of nonlinear plasma wake fields
format: journal article
publisher: Physical Review A
year: 1989
7 authors: J.B. Rosenzweig | P. Schoessow | B. Cole | W. Gai | R. Konecny | J. Norem | 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 schemes is discussed.
keywords:
Download | Details | Edit | Delete
title: Envelope Instability in Low-Energy Proton Synchrotrons
format: journal article
publisher: Nuclear Instruments & Methods A
year: 1990
2 authors: P. Zhou | J.B. Rosenzweig
abstract: In this paper we investigate the limits on beam intensity in low-energy proton synchrotrons due to the instability of the beam envelope. This instability has been previously examined in the context of space charge dominated ion beams, in particular for inertial confinement fusion applications. We generalize the formalism of beam envelope evolution to include effects found in circular accelerators, i.e. curvature focusing and momentum dispersion. Several example lattices are analyzed to determine intensity limits imposed by onset of envelope instability; it is found that the instability can occur without depressing the phase advance below 90-degrees per cell.
keywords:
Download | Details | Edit | Delete
title: High Energy Gain of Trapped Electrons in a Tapered, Diffraction-Dominated Inverse-Free-Electron Laser
format: journal article
publisher: Physical Review Letters
year: 20 April 2005
17 authors: P. Musumeci | S. Ya. Tochitsky | S. Boucher | C. Clayton | A. Doyuran | R. J. England | C. Joshi | C. Pellegrini | J. E. Ralph | J.B. Rosenzweig | C. Sung | Tolmachev, S. | G. Travish | A. A. Varfolomeev | A. A. Varfolomeev | T. Yarovoi | R. B. Yoder
abstract: Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an inverse-freeelectron-laser (IFEL) accelerator experiment. A 14.5 MeVelectron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and field amplitude. The Rayleigh range of the laser, 1:8 cm, is much shorter than the undulator length yielding a diffraction-dominated interaction. Experimental results on the dependence of the acceleration on injection energy, laser focus position, and laser power are discussed. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV=m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator.
keywords:
Download | Details | Edit | Delete
title: Calculation of Coherent Radiation from Ultra-short Electron Beams Using a Li
format: journal article
publisher: AIP
year: 2004
6 authors: A. Flacco | M. Fairchild | Sven Reiche | J.B. Rosenzweig | L. Giannessi | M. Quattromini
abstract: The coherent radiation emitted by electrons in high brightness beam-based experiments is important from the viewpoints of both radiation source development, and the understanding and diagnosing the basic physical processes important in beam manipulations at high intensity. While much theoretical work has been developed to aid in calculating aspects of this class of radiation, these methods do not often produce accurate information concerning the experimentally relevant aspects of the radiation. At UCLA, we are particularly interested in coherent synchrotron radiation and the related phenomena of coherent edge radiation, in the context of a fs-beam chicane compression experiment at the BNL ATF. To analyze this and related problems,we have developed aprogramthat acts as an extension to the Li
keywords:
Download | Details | Edit | Delete
title: Towards Short Wavelength FELs Workshop: Highlights and Implications for PBPL
format: journal article
publisher:
year: May 1993
1 author: G. Travish
abstract: A two day meeting was h eld at Brookhaven (May 21, 22) to discuss the future of short wavelenght FEL work. Various groups presented current work, next step plans and future proposals. Working groups were formed to do paper designs of a facility to produce ~1000A light at significant power levels. All designs attempted to use existing hardware. Final designs were all estimated to cost over $5M. This has significant implications for the future of FEL experimetns. It was also agreed that existing facilities should be supported in order to obtain useful results as soon as possible. This has significant and positive implications for the UCLA experiments.
keywords:
Details | Edit | Delete
title: Nonlinear plasma dynamics in the plasma wake-field accelerator
format: journal article
publisher: Physical Review Letters
year: 1987
1 author: J.B. Rosenzweig
abstract: Excitation of nonlinear plasma oscillations by an intense ultrarelativistic electron beam is considered. It is shown, by analytical solutions of the one-dimensional relativistic fluid equations, that under certain conditions on the relative electron-beam and plasma densities extremely large longitudinal electric fields can be generated in the beam's wake. This scheme is a nonlinear version of the plasma wake-field accelerator, and is predicted to have advantages over the linear regime. (9 References).
keywords:
Download | Details | Edit | Delete
title: Trapping, thermal effects, and wave breaking in the nonlinear plasma wake-field accelerator
format: journal article
publisher: Physical Review A
year: 1988
1 author: J.B. Rosenzweig
abstract: In this paper the author discusses a variety of physical aspects of the nonlinear regime of the plasma wake-field accelerator: general nonlinear properties, thermal effects, particle trapping, and maximum acceleration. The unifying motivation for this investigation is to discover the limit on the size of the plasma waves, as the interesting characteristics of the nonlinear scheme depend strongly on amplitude. Implications for laboratory and cosmic-ray acceleration are discussed. (20 References).
keywords:
Download | Details | Edit | Delete
title: Multiple-fluid models for plasma wake-field phenomena
format: journal article
publisher: Physical Review A
year: 1989
1 author: J.B. Rosenzweig
abstract: In this paper the author presents various treatments of plasma wake-field phenomena which employ multiple-fluid models. These models generalize the one-dimensional, nonlinear, relativistic single-fluid model which has been used extensively in previous plasma wake-field calculations. Using a two-fluid model, the author discusses the interaction of a low-energy continuous electron beam with wake-field-generated plasma waves. The phenomena of continuous-beam modulation and wave period shortening are discussed. The relationship between these effects and the two-stream instability is also examined. Also, using a three-fluid model, effects due to plasma electron temperature in nonlinear plasma wake-fields are examined and compared to previous work. Finally, the consequences of ion motion induced by large-amplitude electron plasma waves are calculated by including the fluid behavior of the ions. (20 References).
keywords:
Download | Details | Edit | Delete
title: Acceleration and focusing of electrons in two-dimensional nonlinear plasma wake fields
format: journal article
publisher: Physical Review A
year: June 4, 1991
4 authors: J.B. Rosenzweig | B. Breizman | T. Katsouleas | J. J. Su
abstract: A new regime of the plasma wake-field accelerator (PWFA) is proposed, in which a high-intensity electron beam is used to excite extremely nonlinear, transverse motion-dominated plasma oscillations. Through computational analysis of the plasma electron motion and the associated wake fields, it is shown that if the beam is dense enough to eject nearly all of the plasma electrons from the beam channel then the short-range wake fields are of excellent quality for acceleration and focusing of electron beams. These results clear up many conceptual difficulties with the practical realization of a PWFA.
keywords:
Download | Details | Edit | Delete
title: Beam optics of a self-focusing plasma lens
format: journal article
publisher: Physical Review D
year: 1989
2 authors: J.B. Rosenzweig | P. Chen
abstract: In this paper the authors analyze the optics of a high-energy beam which is focused by its own wakefields in a plasma. They calculate the effects of lens aberrations on the focusing strength of the lens and on the dilution of the beam's phase space. From this they derive the minimum spot size achievable using a bi-Gaussian beam and, after inclusion of the beam-beam pinch effect, the luminosity enhancement that can be gained in principle. They estimate the luminosity enhancement in the case of SLAC Linear Collider beam design parameters, and discuss limitations and possible improvements in plasma-lens performance. (7 References).
keywords:
Download | Details | Edit | Delete
title: Non-Resonant Beat-Wave Excitation of Constant Phase-Velocity, Relativistic Plasma Waves for Charged-Particle Acceleration
format: journal article
publisher:
year: 2004
10 authors: C. V. Filip | R. Narang | S. Ya. Tochitsky | C. E. Clayton | P. Musumeci | R. B. Yoder | K. A. Marsh | J.B. Rosenzweig | C. Pellegrini | C. Joshi
abstract: The nonresonant beat-wave excitation of relativistic plasma waves is studied in two-dimensional simulations and experiments. It is shown through simulations that, as opposed to the resonant case, the accelerating electric fields associated with the nonresonant plasmons are always in phase with the beat-pattern of the laser pulse. The excitation of such nonresonant relativistic plasma waves is shown to be possible for plasma densities as high as 14 times the resonant density. The density fluctuations and the fields associated with these waves have significant magnitudes, facts confirmed experimentally using collinear Thomson scattering and electron injection, respectively. The applicability of these results towards eventual phase-locked acceleration of prebunched and externally injected electrons is discussed.
keywords:
Download | Details | Edit | Delete
title: Transverse equilibria and luminosity enhancement in linear collider beam-beam collisions
format: journal article
publisher: Physical Review E
year: March 8, 1994
2 authors: J.B. Rosenzweig | P. Chen
abstract:
keywords:
Download | Details | Edit | Delete
title: Physics with and physics of colliding electron beams
format: journal article
publisher: Comments on Nuclear & Particle Physics
year: 1970
2 authors: C. Pellegrini | A. M. Sessler
abstract: The first section of this article deals with the physics that can be done with colliding beams. Experiments which have been already performed and those planned for the future are reviewed. The second section discusses the physics of colliding electron ring devices.
keywords:
Download | Details | Edit | Delete
title: Transverse Particle Motion in Radio-Frequency Linear Accelerators
format: journal article
publisher: Physical Review E
year: 1993
2 authors: J.B. Rosenzweig | L. Serafini
abstract: The transverse motion of a relativistic charged particle in a radio-frequency linear accelerator (rf linac) is examined. The spatially averaged equations of motion derived for the motion in a periodic accelerating cavity system, and solved exactly in the ultra-relativistic limit. These soluction, along with an impulse treatment of the transients at the entrance and exit and exit of the linac cavities, allow derivation of a linear transport matrix throuigh the cavity. This generalized matrix is imporved over previously derived results in that it is applicable to both travelling and standing wave structures, allows for arbitrary injection phase and spatial harmonic content of the rf fields, and is more accurate in approximating the exact charged particle motion.
keywords:
Download | Details | Edit | Delete
title: Experimental observation of plasma wake-field acceleration
format: journal article
publisher: Physical Review Letters
year: 1988
9 authors: J.B. Rosenzweig | D.B. Cline | B. Cole | H. Figueroa | W. Gai | R. Konecny | J. Norem | P. Schoessow | J. Simpson
abstract: The authors report the first experimental test of the physics of plasma wake-field acceleration performed at the Argonne National Laboratory Advanced Accelerator Test Facility. Megavolt-per-meter plasma wake fields are excited by a intense 21-MeV, multipicosecond bunch of electrons in a plasma of density n/sub e/ approximately=10/sup 13/ cm/sup -3/, and probed by a low-intensity 15-MeV witness pulse with a variable delay time behind the intense bunch. Accelerating and deflecting wake-field measurements are presented, and the results compared to theoretical predictions. (8 References).
keywords:
Download | Details | Edit | Delete
title: Diamagnetic fields due to finite-dimension intense beams in high-gain free-electron lasers
format: journal article
publisher: Physical Review E
year: 1998
2 authors: J.B. Rosenzweig | P. Musumeci
abstract: High-gain, self-amplified spontaneous emission free-electron lasers (SASE FEL's), with proposed operation in wavelengths extending down to X-rays, require intense relativistic electron beams, which under certain conditions can generate large diamagnetic fields. The action of these fields has the potential to seriously degrade FEL performance. It is shown here by both analysis and simulation that the finite size of the electron beams diminishes this effect so that it is negligible for proposed SASE FEL's. . (12 References).
keywords:
Download | Details | Edit | Delete
title: Quantum effects in high-gain free-electron lasers
format: journal article
publisher: Physical Review E
year: 2001
3 authors: C.B. Schroeder | C. Pellegrini | P. Chen
abstract: A many-particle fully quantized theory for a free-electron laser which is valid in the high-gain regime is presented. We examine quantum corrections for the high-gain single-pass free-electron laser. It is shown that quantum effects become significant when the photon energy becomes comparable to the gain bandwidth. The initiation of the free-electron laser process from quantum fluctuations in the position and momentum of the electrons is considered, and the parameter regime for enhanced start-up is identified. Photon statistics of the free-electron laser radiation are discussed, and the photon number statistics for the self-amplified spontaneous emission are calculated. (21 References).
keywords:
Download | Details | Edit | Delete
title: Envelope analysis of intense relativistic quasilaminar beams in RF photoinjectors: a theory of emittance compensation
format: journal article
publisher: Physical Review E
year: 1997
2 authors: L. Serafini | J.B. Rosenzweig
abstract: In this paper we provide an analytical description for the transverse dynamics of relativistic, space-charge-dominated beams undergoing strong acceleration, such as those typically produced by RF photoinjectors. These beams are chiefly characterized by a fast transition, due to strong acceleration, from the nonrelativistic to the relativistic regime in which the initially strong collective plasma effects are greatly diminished. However, plasma oscillations in the transverse plane are still effective in significantly perturbing the evolution of the transverse phase space distribution, introducing distortions and longitudinal-transverse correlations that cause an increase in the rms transverse emittance of the beam as a whole. The beam envelope evolution is dominated by such effects and not by the thermal emittance, and so the beam flow can be considered quasilaminar. The model adopted is based on the rms envelope equation, for which we find an exact particular analytical solution taking into account the effects of linear space-charge forces, external focusing due to applied as well as ponderomotive RF forces, acceleration, and adiabatic damping, in the limit that the weak nonlaminarity due to the thermal emittance may be neglected. This solution represents a special mode for beam propagation that assures a secularly diminishing normalized rms emittance and it represents the fundamental operating condition of a space-charge-compensated RF photoinjector. The conditions for obtaining emittance compensation in a long, integrated photoinjector, in which the gun and linac sections are joined, as well as in the case of a short gun followed by a drift and a booster linace, are examined.
keywords:
Download | Details | Edit | Delete
title: Hamiltonian model of a free electron laser
format: journal article
publisher: Optics Communications
year: 1987
3 authors: R. Bonifacio | F. Casagrande | C. Pellegrini
abstract: Both the Compton and the Raman regimes of a free electron laser are described by a relativistic Hamiltonian which originates the evolution equations for 2N+2 canonically conjugate electron and field variables, with the space coordinate as the independent variable. Space charge and field contribution to electron transverse velocity are included. Scaled variables are introduced which allow for a description of the behaviour of the system in terms of a single electron-beam parameter. (16 References).
keywords:
Download | Details | Edit | Delete
title: A study on the choice of parameters for a high energy electron ring accelerator
format: journal article
publisher: Particle Accelerators
year: 1971
2 authors: C. Bovet | C. Pellegrini
abstract: The production of high energy (multi-GeV) proton beams by an electron ring accelerator is considered. Both the final energy and intensity of the proton beam depend on the choice of parameters for the electron ring. Possible sets of parameters, consistent with all the known requirements of ring stability, and which optimize the energy and (or) the intensity of the proton beam, are presented. (19 References).
keywords:
Download | Details | Edit | Delete
title: A study on the conditions required for the transverse stability of a coasting beam in proton storage rings
format: journal article
publisher: Particle Accelerators
year: 1982
2 authors: M. Cornacchia | C. Pellegrini
abstract: A theory is developed that allows calculation of the threshold current of a coasting beam in a circular accelerator or storage ring for an arbitrary frequency versus momentum curve. This theory is applied to the simple case of a parabolic term in the curve, for which an analytical solution of the stability problem is obtained. The general case of an arbitrary frequency distribution is then solved numerically, and the solution used to study the stability of a coasting beam in a high-energy proton storage ring like ISABELLE during the stacking process and for a full-intensity beam. This is done for different momentum distribution curves and includes the effect of the nonlinear space-charge term and of up to sixteen independent magnetic multipoles. The algorithm allows calculation of both the number and the strength of the magnetic multipoles needed to provide a stable beam of the desired current. (8 References).
keywords:
Download | Details | Edit | Delete
title: Experimental Demonstration of Wake-Field Effects in Dielectric Structures
format: journal article
publisher: Physical Review Letters
year: 1988
7 authors: W. Gai | P. Schoessow | B. Cole | R. Konecny | J. Norem | J.B. Rosenzweig | J. Simpson
abstract: We have measured the wake fields induced by short, intense relativistic electron bunches in a slow-wave structure consisting of a dielectric-lined tube, as a test of the dielectric wake-field acceleration mechanism. These fields were used to accelerate a second electron bunch which followed the driving bunch at a variable distance. Results are presented for different dielectrics and beam intensities, and are compared with theoretical predictions.
keywords:
Download | Details | Edit | Delete
title: Measurements of gain larger than 10(5) at 12 mu m in a self-amplified spontaneous-emission free-electron laser
format: journal article
publisher: Physical Review Letters
year: 1998
13 authors: M. Hogan | C. Pellegrini | J.B. Rosenzweig | S. Anderson | Pedro Frigola | A. Tremaine | C. Fortgang | D. C. Nguyen | R. L. Sheffield | J. Kinross-Wright | A. A. Varfolomeev | S. Tolmachev | R. Carr
abstract: We report measurements of very large output intensities corresponding to a gain larger than 10/sup 5/ for a single pass free-electron laser operating in the self-amplified spontaneous emission (SASE) mode at 12 mu m. We also report the 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. (18 References).
keywords:
Download | Details | Edit | Delete
title: On a new instability in electron-positron storage rings (the head- tail effect)
format: journal article
publisher: Nuovo Cimento A
year: 1969
1 author: C. Pellegrini
abstract: It is shown that a bunched electron or positron beam of a storage ring can become unstable because of an effect not previously considered; the instability is due to the regenerative effect introduced by synchrotron oscillations, which enhances the action on the beam of rapidly decaying electromagnetic signals excited by the beam itself on its surrounding media. The results obtained show that the effect can produce instabilities for small beam currents (in the milliampere range), and that it can be influenced and reduced by properly choosing some parameters of the storage ring.
keywords:
Download | Details | Edit | Delete
title: The equilibrium length of high-current bunches in electron storage rings
format: journal article
publisher: Nuovo Cimento A
year: 1971
2 authors: C. Pellegrini | A. M. Sessler
abstract: The consequence of electrical interaction with various resonant structures is expressed in terms of quadratures over the impedance of the structures, and impedance functions for a variety of elements are evaluated. It is shown that elements having resonances at high frequency can, above transition, cause bunches to increase in length with increasing current. The parametric dependence of the bunch lengthening is found to be in good agreement with observations, and numerical estimates, which are in substantial agreement with experiment are presented. (16 References).
keywords:
Download | Details | Edit | Delete
title: Experimental studies of plasma wake-field acceleration and focusing
format: journal article
publisher: Physica Scripta
year: 1990
10 authors: J.B. Rosenzweig | B. Cole | C. Ho | W. Gai | R. Konecny | S. Mtingwa | J. Norem | M. Rosing | P. Schoessow | J. Simpson
abstract: The Plasma Wake-field Accelerator (PWFA) 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 large amplitude plasma wake-fields are of interest in the laboratory, both for the wealth of basic nonlinear plasma wave phenomena which can be studied, as well as for the applications of acceleration and focusing of electrons and positrons in linear colliders. Plasma wake-field waves are also of importance in nature, due to their possible role in direct cosmic ray acceleration. The purpose of the present work is to review the experimental advances made in PWFA research at Argonne National Laboratory, in which many interesting beam and plasma phenomena have been observed. Emphasis is given to discussion of the nonlinear aspects of the PWFA beam-plasma interaction. (29 References).
keywords:
Download | Details | Edit | Delete
title: Demonstration of Electron-Beam Self-Focusing in Plasma Wake Fields
format: journal article
publisher: Physics of Fluids B-Plasma Physics
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:
keywords:
Download | Details | Edit | Delete
title: Adjustable, short focal length permanent-magnet quadrupole based electron beam final focus system
format: journal article
publisher: Physical Review Special Topics - Accelerators and Beams
year: 2005
9 authors: J. K. Lim | P. Frigola | G. Travish | J.B. Rosenzweig | S. Anderson | W. J. Brown | J.S. Jacob | C.L. Robbins | A.M. Tremaine
abstract: Advanced high-brightness beam applicaitons such as inverse-Compton scattering (ICS) depend on achieving of ultra-small spot sizes in high current beams. Modern injectors and compressors enable the production of high-brightness beams having needed short bunch lengths and small emittances. Along with these beam properties comes the need to produce tighter foci, using stronger, shorter focal length optics. An approach to creating such strong focusing-systems using high field, small-bore permanent-magnet quadrupoles (PMQs) is reported here. A final focus system employing three PMQs, each composed of 16 neodymium iron boride sectors in a Halbach geometry has been installed in the PLEIADES ICS experiment. The field gradient in these PMQs is 560 T/m, the highest ever reported in a magnetic optics system. As the magnets are of a fixed field-strength, the focusing system is tuned by adjusting the position of the three magnets along the beamline axis, in analogy to familiar camera optics. This paper discusses the details of the focusing system, simulation, design, fabrication and experimental procedure in creating ultra-small beams at PLEIADES.
keywords:
Download | Details | Edit | Delete
title: Short wavelength FELs using the SLAC linac
format: journal article
publisher: presented at the Fourth European Particle Acclerator Conference (EPAC'94), London, England, June 27-Julyy 1, 1994
year: 1994
30 authors: J. Cobb | D. Prosnitz | V. Vylet | J. Seeman | P. Pianetta | P. Morton | H. D. Nuhn | K. Bane | R. Boyce | G. Loew | R. Miller | J. Paterson | D. Palmer | T. Raubenheimer | R. Tatchyn | H. Winick | A. D. Yeremian | C. Pellegrini | J.B. Rosenzweig | G. Travish | E. T. Scharlemann | W. M. Fawley | K. Halbach | K. J. Kim | R. Schlueter | Sessler, A. M. | M. Xie | R. Bonifacio | L. De Salvo | P. Pierini
abstract: We have studied the use of the SLAC linac to drive FELs at wavelengths down to a few angstroms. Lasing would be achieved in a single pass of a low emittance, high peak current, high energy eelctron beam through a long undulator by Self-Amplified-Spontaneous-Emissin (SASE). About 10(13) photons per pulse can be produced in 100 fs pulses at a 120 Hz rate, corresponding to brightness levels of about 10(22) average and 10(32) peak. Peak power levels are tens of GW. Electron energies of 10-20 GeV are required. Signifcant imporvement of FEL performance seems possible using harmonic generation techniques according to results from numerical simulations.
keywords:
Download | Details | Edit | Delete
title: Theory of a free-electron laser with a Gaussian optical undulator
format: journal article
publisher: IEEE Journal of Quantum Electronics
year: 1988
4 authors: J.C. Gallardo | R. C. Fernow | Palmer, R. B. | C. Pellegrini
abstract: A theoretical study of the possibility of a free-electron laser in the XUV and soft X-ray region of the spectrum, using a counterpropagaing CO/sub 2/ laser beam as an undulator, is presented. A one-dimensional model is used to evaluate the single-pass power gain of such a device. The detrimental effects due to the energy speed, emittance of the electron beam, and the diffraction of the electromagnetic undulator are explicitly incorporated in the formalism. An oscillator experiment is also considered. The solutions of the optical pulse evolution equation in the weak field, low gain, and long-electron-pulse regimes are all derived. (27 References).
keywords:
Download | Details | Edit | Delete
title: Colliding-beam accelerators
format: journal article
publisher: Annual review of nuclear science. Vol. 22.
year: 1972
1 author: C. Pellegrini
abstract: Three electron-positron storage rings for colliding beams at Frascati, Novosibirsk, and Orsay, and one proton-proton storage ring at CERN, are now operating, and a large number of high energy physics experiments are being performed on them. The successful operation of these storage rings has given to physicists the possibility of using colliding beams to reach very high center of mass energies applicable to the study of elementary particle reactions. The intersecting storage ring (ISR) at CERN and Adone at Frascati presently provide the maximum center of mass energies (56 and 3 GeV respectively) for proton-proton and electron-positron interactions. The author discusses single particle motion in storage rings, limits on stored current and current density, beam lifetime, luminosity and its limitations, and coherent instabilities. (76 References).
keywords:
Download | Details | Edit | Delete
title: Optical klystron configuration for a high gain X-ray free-electron laser
format: journal article
publisher: Optics Communications
year: 1990
2 authors: J.C. Gallardo | C. Pellegrini
abstract: The authors present theory and numerical simulations of the performance of an X-ray free-electron laser in the amplified spontaneous emission mode with an optical klystron undulator configuration. This device can produce picosecond pulses of high brightness with a significantly shorter undulator than a conventional FEL. (13 References).
keywords:
Download | Details | Edit | Delete
title: The free-electron laser and its possible developments
format: journal article
publisher: Synchrotron radiation research
year: 1980
1 author: C. Pellegrini
abstract: The operation of a free-electron laser has been discussed, emphasising its capabilities and limitations. The treatment was mainly concerned with operating the laser in an electron storage ring, including stimulated emission by relativistic electrons and in wiggler magnets. Some recent experiments at Stanford were reviewed (see e.g. Elias et al., 1976 and Deacon et al., 1977). (42 References).
keywords:
Download | Details | Edit | Delete
title: Time and frequency domain analysis of superradiant coherent synchrotron radiation in a waveguide free-electron laser
format: journal article
publisher: Physical Review Letters
year: 1994
6 authors: A. Gover | F. V. Hartemann | G.P. Le Sage | N. C. Luhmann | R.S. Zhang | C. Pellegrini
abstract: The coherent synchrotron radiation process in a waveguide is theoretically investigated. A single, short bunch propagating through a wiggler is considered. In a waveguide, two very distinct regimes are possible. At grazing, where the beam velocity matches the wave group velocity, the bunch emits a single, ultrashort chirped pulse whose duration is determined by the interaction bandwidth and the waveguide dispersion. Away from grazing, where slippage dominates, two distinct pulses are radiated at the Doppler upshifted and downshifted frequencies. Both the time and frequency domain expressions for the radiation characteristics are derived. (13 References).
keywords:
Download | Details | Edit | Delete
title: The UCLA Phi-Factory Project
format: journal article
publisher:
year: 1991
1 author: C. Pellegrini
abstract:
keywords:
Details | Edit | Delete
title: Experimental demonstration of dynamic focusing of a relativistic electron bunch by an overdense plasma lens
format: journal article
publisher: Physical Review Letters
year: 1994
7 authors: G. Hairapetian | P. Davis | C. E. Clayton | C. Joshi | S. C. Hartman | C. Pellegrini | T. Katsouleas
abstract: Dynamic focusing of a 3.8 MeV electron bunch, a few collisionless skin depths long approximately 3c/ omega /sub p/, by an overdense, thick plasma lens has been demonstrated. Because of electron inertial effects, the head of the bunch is virtually unaffected by the lens while the rest is focused to varying degree. Time-resolved measurements performed 31 cm downstream of the plasma lens show that, in time, the bunch pinches from an initial size of 2.7 mm (FWHM) to about 0.57 mm and then expands, in reasonable agreement with theory. (20 References).
keywords:
Download | Details | Edit | Delete
title: Coherent and Collective States in Beam-Radiation Interaction
format: journal article
publisher:
year: 1998
1 author: C. Pellegrini
abstract: We review the theory of the free-electron laser collective instability, and the properties of the electron beam and the radiation feild state produced by the instability. We also present some recent experimental results supporting the theory.
keywords:
Details | Edit | Delete
title: Ponderomotive focusing in axisymmetric RF linacs
format: journal article
publisher: Physical Review E
year: 1993
2 authors: S. C. Hartman | J.B. Rosenzweig
abstract: In many present and planned compact electron sources and linacs, very large rf accelerating fields are present in the linac structures. A charged particle whose trajectory is parallel to the axis receives no net focusing from the periodic transverse forces arising from the axisymmetric rf wave. However, if the lowest-order periodic transverse motion of the particles is included, a net ponderomotive focusing force is obtained when the momentum transfer is averaged over a period of the motion. Since this force is second order in the electric-field amplitude, the resultant focusing can be non-negligible in high gradient structures. In order to produce and preserve high-brightness beams in rf linacs it is necessary to obtain a better understanding of all the forces acting on the beam and the subsequent beam dynamics. To this end we examine the lowest-order ponderomotive rf focusing of electrons in axisymmetric standing- and traveling-wave linac structures. We obtain a generalized paraxial envelope equation which includes the effects of the ponderomotive focusing and longitudinal acceleration to describe the transverse beam envelope evolution. The implications of our results on beam dynamics in electron linacs are examined, and extensions of the results to positron and proton linacs are discussed.
keywords:
Download | Details | Edit | Delete
title: Diffraction radiation defocussing of an electron ring
format: journal article
publisher: Nuclear Instruments & Methods
year: 1971
3 authors: E. Keil | C. Pellegrini | A. M. Sessler
abstract: The influence upon axial stability in an electron ring of the diffraction radiation reaction force, generated by a ring moving in an acceleration column, is calculated theoretically. A stability criterion is obtained, and numerical examples show that the criterion is not an important constraint upon the choice of parameters or the operation of an electron ring accelerator.
keywords:
Download | Details | Edit | Delete
title: Beam-cavity interaction in electron storage rings
format: journal article
publisher: Nuclear Instruments & Methods
year: 1975
4 authors: E. Keil | C. Pellegrini | A. Turrin | M. Sessler
abstract: A formal expression is obtained for the energy loss per turn, of a rigid bunch of electrons, to a closed cylindrical cavity with quality factor Q. The expression is valid provided the diameter of the entrance and exit ports for the beam are small compared to the bunch length. The effect of the ports is studied in an independent computational method. The energy loss is numerically evaluated for a range of parameters of interest to electron storage rings. (13 References).
keywords:
Download | Details | Edit | Delete
title: On Some Distinctiveness of the Kurchatov-UCLA Undulator Scheme Providing Strong Magnetic Fields for Short Periods
format: journal article
publisher:
year: September 1991
2 authors: C. Pellegrini | A. A. Varfolomeev
abstract: We present a qualitative analysis of the new scheme for the Kurchatov large field strengh short period undulator installed at UCLA and compare it with some hybrid schemes suggested by other laboratories. We show that beyond the apparent similarity important differences exist between these devices. As a result our design provides a higher saturation limit for the undulator magnetic fields.
keywords:
Details | Edit | Delete
title: High efficiency, multiterawatt x-ray free electron lasers
format: journal article
publisher: Physical Review Accelerators and Beams
year: 2016
4 authors: C. Emma | K. Fang | J. Wu | C. Pellegrini
abstract: In this paper we present undulator magnet tapering methods for obtaining high efficiency and multiterawatt peak powers in x-ray free electron lasers (XFELs), a key requirement for enabling 3D atomic resolution single molecule imaging and nonlinear x-ray science. The peak power and efficiency of tapered XFELs is sensitive to time dependent effects, like synchrotron sideband growth. To analyze this dependence in detail we perform a comparative numerical optimization for the undulator magnetic field tapering profile including and intentionally disabling these effects. We show that the solution for the magnetic field taper profile obtained from time independent optimization does not yield the highest extraction efficiency when time dependent effects are included. Our comparative optimization is performed for a novel undulator designed specifically to obtain TW power x-ray pulses in the shortest distance: superconducting, helical, with short period and built-in strong focusing. This design reduces the length of the breaks between modules, decreasing diffraction effects, and allows using a stronger transverse electron focusing. Both effects reduce the gain length and the overall undulator length. We determine that after a fully time dependent optimization of a 100 m long Linac coherent light source-like XFEL we can obtain a maximum efficiency of 7%, corresponding to 3.7 TW peak radiation power. Possible methods to suppress the synchrotron sidebands, and further enhance the FEL peak power, up to about 6 TW by increasing the seed power and reducing the electron beam energy spread, are also discussed.
keywords:
Download | Details | Edit | Delete
title: One-dimensional numerical simulation of a free electron laser-storage ring system
format: journal article
publisher: Journal of Applied Physics
year: 1984
2 authors: A. Luccio | C. Pellegrini
abstract: A numerical simulation of a free electron laser oscillator-storage ring system is presented. The model describes the evolution of the system toward a steady state and gives information on the change of the laser power and of the electron and photon pulse shape during the transient. The steady-state laser power output and electron beam properties are compared with the existing theoretical model. (17 References).
keywords:
Download | Details | Edit | Delete
title: Exponential gain and saturation of a self-amplified spontaneous emission free-electron laser
format: journal article
publisher: Science
year: 2001
32 authors: S. V. Milton | E. Gluskin | N. D. Arnold | C. Benson | W. Berg | S. G. Biedron | M. Borland | Y. C. Chae | R. J. Dejus | P.K. Den Hartog | B. Deriy | M. Erdmann | Y. I. Eidelman | M. W. Hahne | Z. Huang | K. J. Kim | J. W. Lewellen | Y. Li | A. H. Lumpkin | O. Makarov | E. R. Moog | A. Nassiri | V. Sajaev | R. Soliday | B. J. Tieman | E. M. Trakhtenberg | G. Travish | I. B. Vasserman | G. Wiemerslage | B. X. Yang | N. A. Vinokurov | X. J. Wang
abstract: Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent X-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational X-ray free-electron laser. (30 References).
keywords:
Download | Details | Edit | Delete
title: Observation of self-amplified spontaneous emission and exponential growth at 530 nm
format: journal article
publisher: Physical Review Letters
year: 2000
50 authors: S. V. Milton | E. Gluskin | S. G. Biedron | R. J. Dejus | P. K. Den Hartog | J. N. Galayda | K. J. Kim | J. W. Lewellen | E. R. Moog | V. Sajaev | N. S. Sereno | G. Travish | N. A. Vinokurov | N. D. Arnold | C. Benson | W. Berg | J. A. Biggs | M. Borland | J. A. Carwardine | Y. C. Chae | G. Decker | B. N. Deriy | M. J. Erdmann | H. Friedsam | C. Gold | A. E. Grelick | M. W. Hahne | K. C. Harkay | Z. Huang | E. S. Lessner | R. M. Lill | A. H. Lumpkin | O. A. Makarov | G. M. Markovich | D. Meyer | A. Nassiri | J. R. Noonan | S. J. Pasky | G. Pile | T. L. Smith | R. Soliday | B. J. Tieman | E. M. Trakhtenberg | G. F. Trento | I. B. Vasserman | D. R. Walters | X. J. Wang | G. Wiemerslage | S. Xu | B. X. Yang
abstract: Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator. (20 References).
keywords:
Download | Details | Edit | Delete
title: The Development of X-ray Free-Electron Lasers
format: journal article
publisher: Selected Topics in Quantum Electronics, IEEE Journal
year: 2004
2 authors: S. Reiche | C. Pellegrini
abstract: We review and discuss the theoretical and experi- mental work that has led to the development of short wavelength free-electron lasers operating as single pass amplifiers, starting from the spontaneous undulator radiation, in the self amplified spontaneous emission mode. This work has led to several projects to build this type of free-electron lasers operating at a wavelength of about 0.1 nm, producing coherent X-ray pulses with an un- precedented brilliance and peak power, and pulse length in the femtosecond range. One such project, the LCLS, is presently under construction and is expected to be operational in 2008. tool to study the properties and structure of matter at the atomic and molecular level for over a century. Using X-rays we have made great progress in understanding the physical properties of materials and living systems. Today, the best sources of X-rays utilize spontaneous synchrotron radiation from relativistic elec- tron beams in storage rings with undulator magnet insertions. The most advanced, so-called third generation sources, are used by thousands of scientists around the world.
keywords:
Download | Details | Edit | Delete
title: Experiments on laser driven beatwave acceleration in a ponderomotively formed plasma channel
format: journal article
publisher: Physics of Plasmas
year: 2004
10 authors: S. Ya. Tochitsky | R. Narang | C. V. Filip | P. Musumeci | C. E. Clayton | R. B. Yoder | K. A. Marsh | J.B. Rosenzweig | C. Pellegrini | C. Joshi
abstract: A 10 ps long beam of 12 MeV electrons is externally injected into a ~3-cm long plasma beatwave excited in a laser ionized hydrogen gas. The electrons have been accelerated to 50 MeV with a gradient of ~1.3 GeV/m. It is shown that when the effective plasma wave amplitude-length product is limited by ionization-induced defocusing (IID), acceleration of electrons is significantly enhanced by using a laser pulse with a duration longer than the time required for ions to move across the laser spot size. Both experiments and two-dimensional simulations reveal that, in this case, self-guiding of the laser pulse in a ponderomotively formed plasma channel occurs. This compensates for IID and drives the beatwave over the longer length compared to when such a channel is not present.
keywords: pbpl  
Download | Details | Edit | Delete
title: Very High Energy Gain at the Neptune Inverse Free Electron Laser Experiment
format: journal article
publisher: AIP Conference Proceedings
year: Dec 2004
16 authors: P. Musumeci | S. Ya. Tochitsky | S. Boucher | A. Doyuran | R. J. England | C. Joshi | C. Pellegrini | J. Ralph | J.B. Rosenzweig | C. Sung | S. Tolmachev | G. Travish | A. A. Varfolomeev | A. Varfolomeev Jr. | T. Yarovoi | R. Yoder
abstract: We report the observation of energy gain in excess of 20 MeV at the Inverse Free Electron Laser Accelerator experiment at the Neptune Laboratory at UCLA. A 14.5 MeV electron beam is injected in an undulator strongly tapered in period and field amplitude. The IFEL driver is a CO2 10.6 m laser with power larger than 400 GW. The Rayleigh range of the laser, ~ 1.8 cm, is much shorter than the undulator length so that the interaction is diffraction dominated. A few per cent of the injected particles are trapped in a stable accelerating bucket. Electrons with energies up to 35 MeV are measured by a magnetic spectrometer. Three-dimensional simulations, in good agreement with the measured electron energy spectrum, indicate that most of the acceleration occurs in the first 25 cm of the undulator, corresponding to an energy gradient larger than 70 MeV/m. The measured energy spectrum also indicates that higher harmonic Inverse Free Electron Laser interaction takes place in the second section of the undulator.
keywords: pbpl  
Download | Details | Edit | Delete
title: Conceptual Design for a 1-GeV IFEL Accelerator
format: journal article
publisher: AIP Conference Proceedings
year: Dec 2004
5 authors: W. D. Kimura | P. Musumeci | D. C. Quimby | S. C. Gottschalk | C. Pellegrini
abstract: A conceptual design for a multistaged 1-GeV IFEL laser-driven accelerator (laser linac) was developed using the Staged Electron Laser Acceleration (STELLA) inverse free electron laser (IFEL) model created at STI Optronics. A comparison with the UCLA TREDI model yields good agreement with the STELLA model. The 1-GeV IFEL laser linac consists of an IFEL buncher for forming microbunches and four IFEL acceleration stages. Electrons enter the laser linac from a conventional microwave-driven linac (51 MeV). The acceleration stages are driven by 10-TW laser beams at 1.06-m. It is found good trapping occurs as the electrons are accelerated; however, refocusing of the e-beam between acceleration stages is needed to control detrapping effects. The energy spread of the trapped electrons is also small. This design exercise was in support of the task placed upon the EM Structure-Based Accelerators Working Group at the 2004 Advanced Accelerator Concepts Workshop. It demonstrates that a 1-GeV IFEL laser linac is feasible with present technology. 2004 American Institute of Physics
keywords: pbpl  
Download | Details | Edit | Delete
title: UCLA Neptune Ramped Electron Bunch Experiment
format: journal article
publisher: AIP Conference Proceedings
year: 2004
5 authors: R. J. England | D. Alesini | A. Doyuran | P. Musumeci | J.B. Rosenzweig
abstract: A ramped electron bunch (i.e. one having a current density which rises linearly from the head to the tail and then drops sharply to zero) has been predicted to be an ideal drive beam for the plasma wake field accelerator due to the large transformer ratio it is capable of generating. A scheme was recently proposed for the creation of a relativistic electron bunch that approximates a ramped current profile [England, et al., AIP Conf. Proc. 647, p.884 (2002)], using a dogleg or dispersionless translating section as a bunch compressor. An experiment is underway at the Neptune laboratory using this scheme to create such a beam. The diagnostic being developed for measuring the temporal profile of the beam is an X-Band transverse deflecting mode cavity. 2004 American Institute of Physics
keywords: pbpl  
Download | Details | Edit | Delete
title: Study of X-ray Harmonics of the Polarized Inverse Compton Scattering Experiment at UCLA
format: journal article
publisher: AIP Conference Proceedings
year: 2004
8 authors: A. Doyuran | J. England | C. Joshi | P. Musumeci | J.B. Rosenzweig | S. Tochitsky | G. Travish | O. Williams
abstract: We propose an Inverse Compton Scattering (ICS) experiment, which will investigate nonlinear properties of the scattering utilizing the terawatt CO2 laser system with various polarizations in Neptune Laboratory at UCLA. When the normalized amplitude of the vector potential a0 is larger than unity the scattering occurs in the nonlinear region; therefore, higher harmonics are also produced. We present a calculation tool for the Double Differential Spectrum (DDS) distribution and total number of photons produced for both head-on and 90 scattering. We decided to do the experiment at 90 to avoid complications due to strong diffraction of the incoming laser. We discuss the electron and laser beam parameters for the experiment. 2004 American Institute of Physics
keywords: pbpl  
Download | Details | Edit | Delete
title: Study of a THz IFEL prebuncher for laser-plasma accelerators
format: journal article
publisher: AIP Conference Proceedings
year: 2004
7 authors: C. Sung | S. Ya. Tochitsky | P. Musumeci | J. Ralph | J.B. Rosenzweig | C. Pellegrini | C. Joshi
abstract: For monoenergetic acceleration of electrons, the injected particles need to be bunched with the same periodicity as the accelerating structure. In a laser-driven plasma beatwave accelerator, the accelerating structure (plasma wave) is phase-locked to the CO2 beat-wave used to drive it. Using the same beat-wave to generate high power FIR radiation via difference frequency mixing in GaAs ensures that the radiation has the same phase relationship as the plasma wave before it saturates and detunes from the pump. Therefore, this radiation can be used to prebunch an existing electron beam based on an Inverse Free Electron Laser (IFEL) concept. Here we report the progress on the proposed THz microbunching experiment in the Neptune laboratory. A 50 cm long prebuncher is optimized using simulation codes for minimum FIR power required. The injected 5ps long electron beam is expected to form a series of 45 m long microbunches containing over 40% of the injected current after 1.6 m drift space following the undulator. Preliminary experimental results on THz generation are also presented.
keywords: pbpl  
Download | Details | Edit | Delete
title: Acceleration of electrons in a diffraction-dominated IFEL
format: journal article
publisher: FEL
year: 2004
16 authors: P. Musumeci | S. Ya. Tochitsky | S. Boucher | A. Doyuran | R. J. England | C. Joshi | C. Pellegrini | J. Ralph | J.B. Rosenzweig | C. Sung | S. Tolmachev | G. Travish | A. A. Varfolomeev | A. Varfolomeev Jr. | T. Yarovoi | R. Yoder.
abstract: We report on the observation of energy gain in excess of 20 MeV at the Inverse Free Electron Laser Accelerator ex- periment at the Neptune Laboratory at UCLA. A 14.5 MeV electron beam is injected in a 50 cm long undulator strongly tapered both in period and field amplitude. A CO2 10.6 ?m laser with power > 300 GW is used as the IFEL driver. The Rayleigh range of the laser ( ? 1.8 cm) is shorter than the undulator length so that the interaction is diffraction dom- inated. Few per cent of the injected particles are trapped in stable accelerating buckets and electrons with energies up to 35 MeV are detected on the magnetic spectrometer. Three dimensional simulations are in good agreement with the electron energy spectrums observed in the experiment and indicate that substantial energy exchange between laser and electron beam only occurs in the first 25-30 cm of the undulator. An energy gradient of > 70 MeV is inferred. In the second section of the undulator higher harmonic IFEL interaction is observed.
keywords: pbpl  
Download | Details | Edit | Delete
title: The SPARX project: R & D Activity towards X-Ray Sources
format: journal article
publisher:
year: 2004
80 authors: D.Alesini | S.Bertolucci | M. Bellaveglia | M.E.Biagini | R.Boni | M.Boscolo | M.Castellano | A.Clozza | G.Di Pirro | A.Drago | A.Esposito | M.Ferrario | D. Filippetto | V.Fusco | A.Gallo | A.Ghigo | S.Guiducci | M.Incurvati | C.Ligi | F.Marcellini | M.Migliorati | A.Mostacci | 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 | F.Alessandria | A.Bacci | I.Boscolo | F.Broggi | S.Cialdi | C.De Martinis | D.Giove | C.Maroli | M. Mauri | V.Petrillo | M. Romè | L.Serafini | M.Mattioli | P. Musumeci | L.Catani | E.Chiadroni | A. Cianchi | C. Schaerf | F.Ciocci | G.Dattoli | A. Di Pace | A.Doria | F.Flora | G.P.Gallerano | L.Giannessi | E.Giovenale | G.Messina | L.Mezi | P.L.Ottaviani | S. Pagnutti | G. Parisi | L.Picardi | M.Quattromini | A.Renieri | C.Ronsivalle | A. Torre | A. Zucchini | S. De Silvestri | M. Nisoli | S. Stagira | J.B. Rosenzweig | S. Reiche | P.Emma
abstract: SPARX is an evolutionary project proposed by a collaboration among ENEA-INFN-CNR-Universita` di Roma Tor Vergata aiming at the construction of a FEL- SASE X-ray source in the Tor Vergata Campus. The first phase of the SPARX project, funded by Government Agencies, will be focused on R&D activity on critical components and techniques for future X-ray facilities as described in this paper.
keywords:
Download | Details | Edit | Delete
title: COMMISSIONING OF STRONG TAPERED UNDULATOR DEVELOPED
format: journal article
publisher:
year: 2004
7 authors: S.V. Tolmachev | A. A. Varfolomeev | A. Varfolomeev Jr. | T.V. Yarovoi | P. Musumeci | C. Pellegrini | J.B. Rosenzweig
abstract: Here we describe the manufactured KIAE-2p planar undulator designed for the Inverse Free Electron Laser experiment at the University of California in Los Angeles. New technology enabled to fabricate the installation responding to the stringent requirements on mechanical construction accuracy and magnetic field strong tapering. Results of the magnetic field measurements by different methods are given. The obtained magnetic field maps were used for final simulations of the acceleration process. It is shown that for nominal electron beam and laser beam parameters up to 30% of electrons can be captured and accelerated from initial 14 MeV up to 52 MeV. Special analysis of the undulator acceptances for these parameters is made. It is shown that the acceleration is possible up to energies >30 MeV for rather wide ranges of laser pulse energy, Rayleigh length and e.b. emittance.
keywords:
Download | Details | Edit | Delete
title: Terahertz IFEL/FEL Microbunching for Plasma Beatwave Accelerators
format: journal article
publisher:
year: 2005
9 authors: C. Sung | S. Ya. Tochitsky | J. Ralph | P. Musumeci | S. Reiche | C. Clayton | J.B. Rosenzweig | C. Pellegrini | C. Joshi
abstract: In order to obtain monoenergetic acceleration of electrons, phase-locked injection using electron microbunches shorter than the accelerating structure is necessary. For a laser-driven plasma beatwave accelerator experiment, we propose to microbunch the electrons by interaction with terahertz (THz) radiation in an undulator via two mechanisms� Free Electron Laser (FEL) and Inverse Free Electron Laser (IFEL). Since the high power FIR radiation will be generated via difference frequency mixing in GaAs by the same CO2 beatwave used to drive the plasma wave, electrons could be phase-locked and pre-bunched into a series of microbunches separated with the same periodicity. Here we examine the criteria for undulator design and present simulation results for both IFEL and FEL approaches. Using different CO2 laser lines, electrons can be microbunched with different periodicity 300 �100 ?m suitable for injection into plasma densities in the range 1016 � 1017 cm-3, respectively. The requirements on the THz radiation power and the electron beam qualities are also discussed.
keywords:
Download | Details | Edit | Delete
title: High Energy gain IFEL at the UCLA Neptune Laboratory
format: journal article
publisher:
year: 2005
16 authors: P. Musumeci | S. Ya. Tochitsky | S. Boucher | A. Doyuran | R. J. England | C. Joshi | C. Pellegrini | J. Ralph | J.B. Rosenzweig | C. Sung | G. Travish | R. Yoder | A. A. Varfolomeev | S. Tolmachev | A. Varfolomeev Jr. | T. Yarovoi
abstract: We report on the observation of energy gain in excess of 20MeV at the Inverse Free Electron Laser Accelerator experiment at the Neptune Laboratory at UCLA. A 14.5MeV electron beam is injected in a 50cm longundulator strongly tapered both in period and field amplitude. A CO210.6?m laser with power > 400GW is used as the IFEL driver. The Rayleigh range of the laser(?1.8cm)is shorter than the undulator length so that the interaction is diffraction dominated. Few per cent of the injected particles are trapped instable accelerating buckets and electrons with energies up to 35 MeV are detected on the magnetic spectrometer. Three dimensional simulations are in good agreement with the electron energy spectrums observed in the experiment and indicate that substantial energy exchange between laser and electron beam only occurs in the first 25-30 cm of the undulator. Anenergygradientof>70MeVisinferred. In these cond section of the undulator higher harmonic IFEL interaction is observed.
keywords:
Download | Details | Edit | Delete
title: RF Measurements results of the final brazed SPARC RF Deflector
format: journal article
publisher:
year: 2007
7 authors: L. Ficcadenti | L. Palumbo | A. Mostacci | D. Alesini | C. Vaccarezza | G. Di Pirro | J.B. Rosenzweig
abstract: The longitudinal phase space and the horizontal beam slice emittance measurements of the SPARC 150MeV-lnC electron beam, foresee the use of a RF deflector. he device is a five cells standing wave structure operating on the TM110-like dipole mode at 2.856Ghz and allows reaching a longitudinal resolution of ~12um with 2MW of peak input power. In the paper we illustrate the RF measurements results on the final brazed copper device.
keywords:
Download | Details | Edit | Delete
title: Optimum Beam Creation in Photoinjectors Using Space-Charge Expansion
format: journal article
publisher:
year: 2006
4 authors: J.B. Rosenzweig | A.M. Cook | M. Dunning | R.J. England
abstract: It has recently been shown that by illuminating a photo- cathode with an ultra-short laser pulse of appropriate trans- verse profile, a uniform density, ellipsoidally shaped bunch is dynamically formed, which then has linear space-charge fields in all dimensions inside of the bunch. We study here this process, and its marriage to the standard emittance compensation scenario that is implemented in most modern photoinjectors. It is seen that the two processes are compat- ible, with simulations indicating that a very high brightness beam can be obtained. The scheme has produced stimulus for a series of experiments at the SPARC injector at Fras- cati in 2006-2007. An initial time-resolved experiment has been performed involving Cerenkov radiation produced at an aerogel. We discuss the results of this preliminary ex- periment, as well as plans for future experiments to resolve the ellipsoidal bunch shape at low energy. Future measure- ments at high energy based on fs resolution RF sweepers are discussed.
keywords: pbpl  
Download | Details | Edit | Delete
title: Future FEL Studies at the VISA Experiment in the SASE and Seeded Modes
format: journal article
publisher:
year: 2006
9 authors: G. Andonian | M.P. Dunning | A. Y. Murokh | C. Pellegrini | S. Reiche | J.B. Rosenzweig | M. Babzien | I. Ben-Zvi | V. Yakimenko
abstract: The VISA (Visible to Infrared SASE Amplifier) experiment at BNL (Brookhaven National Laboratory) has previously demonstrated saturation at 840 nm in 2001. Further SASE studies, in 2003, have demonstrated an anomalously large bandwidth spread of the FEL spectrum due to off-angle emissions. This paper disseminates the current and future program of the VISA program at BNL. This includes a study of a seeded FEL, using a 1 micron YAG laser as a seed, and the accompanying diagnostics to characterize the radiation. Diagnostics include the double differential spectrometer, a mode converter to investigate the orbital angular momentum of light in the FEL, and an optical pepper-pot for coherence measurements. As usual, start-to-end simulations are presented.
keywords: pbpl  
Download | Details | Edit | Delete
title: Experimental characterization of the transverse phase space of a 60-MeV electron beam through a compressor chicane
format: journal article
publisher:
year: 2006
8 authors: F. Zhou | A. Kabel | J.B. Rosenzweig | R. Agustsson | G. Andonian | D. Cline | A. Murokh | V. Yakimenko
abstract: Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV.
keywords: pbpl  
Download | Details | Edit | Delete
title: Seeded free-electron and inverse free-electron laser techniques for radiation amplification and electron microbunching in the terahertz range
format: journal article
publisher: Physical Review Letters
year: 22 December 2006
6 authors: C. Sung | S. Ya. Tochitsky | S. Reiche | J.B. Rosenzweig | C. Pellegrini | C. Joshi
abstract: A comprehensive analysis is presented that describes amplification of a seed THz pulse in a single-pass free-electron laser (FEL) driven by a photoinjector. The dynamics of the radiation pulse and the modulated electron beam are modeled using the time-dependent FEL code, GENESIS 1.3. A 10-ps (FWHM) electron beam with a peak current of 50100 A allows amplification of a 1 kWseed pulse in the frequency range 0.53 THz up to 10100 MW power in a relatively compact 2-m long planar undulator. The electron beam driving the FEL is strongly modulated, with some inhomogeneity due to the slippage effect. It is shown that THz microbunching of the electron beam is homogeneous over the entire electron pulse when saturated FEL amplification is utilized at the very entrance of an undulator. This requires seeding of a 30-cm long undulator buncher with a 13 MW of pump power with radiation at the resonant frequency. A narrow-band seed pulse in the THz range needed for these experiments can be generated by frequency mixing of CO2 laser lines in a GaAs nonlinear crystal. Two schemes for producing MW power pulses in seeded FELs are considered in some detail for the beam parameters achievable at the Neptune Laboratory at UCLA: the first uses a waveguide to transport radiation in the 0.53 THz range through a 2-m long FEL amplifier and the second employs high-gain third harmonic generation using the FEL process at 39 THz.
keywords: pbpl  
Download | Details | Edit | Delete
title: Experimental characterization of an ultrafast Thomson scattering x-ray source with three-dimensional time and frequency-domain analysis
format: journal article
publisher:
year: 2004
18 authors: W. J. Brown | S. G. Anderson | C. P. J. Barty | S. M. Betts | R. Booth | J. K. Crane | R. R. Cross | D. N. Fittinghoff | D. J. Gibson | F. V. Hartemann | E. P. Hartouni | J. Kuba | G.P. Le Sage | D. R. Slaughter | A. M. Tremaine | A. J. Wootton | P. T. Springer | J.B. Rosenzweig
abstract: We present a detailed comparison of the measured characteristics of Thomson backscattered xrays produced at the Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures facility at Lawrence Livermore National Laboratory to predicted results from a newly developed, fully three-dimensional time and frequency-domain code. Based on the relativistic differential cross section, this code has the capability to calculate time and space dependent spectra of the x-ray photons produced from linear Thomson scattering for both bandwidth-limited and chirped incident laser pulses. Spectral broadening of the scattered x-ray pulse resulting from the incident laser bandwidth, perpendicular wave vector components in the laser focus, and the transverse and longitudinal phase spaces of the electron beam are included. Electron beam energy, energy spread, and transverse phase space measurements of the electron beam at the interaction point are presented, and the corresponding predicted x-ray characteristics are determined. In addition, time-integrated measurements of the xrays produced from the interaction are presented and shown to agree well with the simulations.
keywords: pbpl  
Download | Details | Edit | Delete
title: Generation and Measurement of Relativistic Electron Bunches Characterizzed by a Linearly Ramped Current Profile
format: journal article
publisher: PRL
year: May 28, 2008
3 authors: R.J. England | J.B. Rosenzweig | G. Travish
abstract: We report the first successful attempt to generate ultrashort (110 ps) relativistic electron bunches characterized by a ramped longitudinal current profile that rises linearly from head to tail and then falls sharply to zero. Bunches with this type of longitudinal shape may be applied to plasma-based accelerator schemes as an optimized drive beam, and to free-electron lasers as a means of reducing asymmetry in microbunching due to slippage. The scheme used to generate the ramped bunches employs an aniso-chronous dogleg beam line with nonlinear correction elements to compress a beam having an initial positive time-energy chirp. The beam current profile is measured using a deflecting mode cavity, and a pseudoreconstruction of the beams longitudinal phase space distribution is obtained by using this diagnostic with a residual horizontal dispersion after the dogleg.
keywords:
Download | Details | Edit | Delete
title: Breakdown Limits on Gigavolt-per-Meter Electron-Beam-Driven Wakefields in Dielectric Structures
format: journal article
publisher:
year: May 27, 2008
15 authors: M.C. Thompson | H. Badakov | A.M. Cook | J.B. Rosenzweig | R. Tikhoplav | G. Travish | I. Blumenfeld | M.J. Hogan | R. Ischebeck | N. Kirby | R. Siemann | D. Walz | P. Muggli | A. Scott | R.B. Yoder
abstract: First measurements of the breakdown threshold in a dielectric subjected to GV=m wakefields produced by short (30 330 fs), 28.5 GeV electron bunches have been made. Fused silica tubes of 100
keywords:
Download | Details | Edit | Delete
title: Experimental Generation and Characterization of Uniformly Filled Ellipsoidal Electron-Beam Distributions
format: journal article
publisher: PRL
year: 2008
5 authors: P. Musumeci | J.T. Moody | R.J. England | J.B. Rosenzweig | T. Tran
abstract: For 40 years, uniformly filled ellipsoidal beam distributions have been studied theoretically, as they hold the promise of generating self-fields linear in the coordinate offset in all three directions. Recently, a scheme for producing such distributions, based on the strong longitudinal expansion of an initially very short beam under its own space-charge forces, has been proposed. In this Letter we present the experimental demonstration of this scheme, obtained by illuminating the cathode in a rf photogun with an ultrashort laser pulse (
keywords: pbpl  
Download | Details | Edit | Delete
title: A Proposal for an X-Ray Free-Electron Laser Oscillator with an Energy-Recovery Linac
format: journal article
publisher: PRL
year: 2008
3 authors: Kwang-Je Kim | Yuri Shvyd'ko | Sven Reiche
abstract: We show that a free-electron laser oscillator generating x rays with wavelengths of about 1 A ? is feasible using ultralow emittance electron beams of a multi-GeV energy-recovery linac, combined with a low-loss crystal cavity. The device will produce x-ray pulses with 109 photons at a repetition rate of 1100 MHz. The pulses are temporarily and transversely coherent, with a rms bandwidth of about 2 meV, and rms pulse length of about 1 ps.
keywords: pbpl  
Download | Details | Edit | Delete
title: Virtual dielectric waveguide mode description of a high-gain free-electron laser. II. Modeling and numerical simulations
format: journal article
publisher: PRA
year: 2008
3 authors: E. Hemsing | A. Gover | J.B. Rosenzweig
abstract: A high-gain free-electron laser is modeled using an expansion of the radiation field in terms of guided Laguerre-Gaussian modes of a virtual dielectric waveguide E. Hemsing, A. Gover, and J. Rosenzweig, preceding paper, Phys Rev. A 77, 063830 2008 . The radiation profile evolution, power gain, and detuning efficiency characteristics are investigated for seeding with fundamental Gaussian and higher-order Laguerre- Gaussian input modes on a Gaussian e-beam in the collective regime. The full wave evolution solution at different seed radiation injection conditions results in determination of the optimal waist size and waist position of the seed radiation beam for maximum power coupling efficiency. Results for guided mode evolution and power gain are shown to be consistent with simulations performed with the code GENESIS 1.3. The amplification and spontaneous generation of FEL radiation with orbital angular momentum is also considered.
keywords: pbpl   pra  
Download | Details | Edit | Delete
title: Virtual dielectric waveguide mode description of a high-gain free-electron laser. I. Theory
format: journal article
publisher: PRA
year: 2008
3 authors: E. Hemsing | A. Gover | J.B. Rosenzweig
abstract: A set of mode-coupled excitation equations for the slowly growing amplitudes of dielectric waveguide eigenmodes is derived as a description of the electromagnetic signal field of a high-gain free-electron laser FEL, including the effects of longitudinal space charge. This approach of describing the field basis set has notable advantages for FEL analysis in providing an efficient characterization of eigenmodes, and in allowing a clear connection to free-space propagation of the input seeding and output radiation. The formulation describes the entire evolution of the radiation wave through the linear gain regime, prior to the onset of saturation, with arbitrary initial conditions. By virtue of the flexibility in the expansion basis, this technique can be used to find the direct coupling and amplification of a particular mode. A simple transformation converts the derived coupled differential excitation equations into a set of coupled algebraic equations and yields a matrix determinant equation for the FEL eigenmodes. A quadratic index medium is used as a model dielectric waveguide to obtain an expression for the predicted spot size of the dominant system eigenmode, in the approximation that it is a single Gaussian mode.
keywords: pbpl   pra  
Download | Details | Edit | Delete
title: Experimental generation and characterization of uniformly filled ellipsoidal beam distributions
format: journal article
publisher: Physical Review Letters
year: 2008
6 authors: P. Musumeci | M.S. Gutierrez | J.T. Moody | C.M. Scoby | J.B. Rosenzweig | T. Tran
abstract: Recently, a scheme for producing ideal uniformly filled ellipsoidal beam distributions, which depends on the strong longitudinal expansion of an initially very short beam under its own space charge forces, has been demonstrated at the UCLA Pegasus Laboratory. Here we present further work on the characterization of this novel regime of operation of a photoinjector. In particular we study the sensitivity of the generation of the uniformly filled ellipsoidal distribution from the initial transverse laser profile. The ultra-high brightness of the beam created operating in this �blow-out� regime is verified obtaining high quality relativistic electron diffraction patterns from thin Al foils.
keywords:
Download | Details | Edit | Delete
title: Longitudinal dispersion of orbital angular momentum modes in high-gain free-electron lasers
format: journal article
publisher: APS
year: July 30, 2008
4 authors: E. Hemsing | Agostino Marinelli | Sven Reiche | J.B. Rosenzweig
abstract: The physical effects of optical mode dispersion in the electron beam of a free-electron laser are investigated for modes that carry orbital angular momentum. The analysis is performed using a derived equivalence between two different formulations that describe the radiation fields in the linear regime.
keywords:
Download | Details | Edit | Delete
title: Helical Electron-Beam Microbunching by Harmonic Coupling in a Helical Undulator
format: journal article
publisher: PRL
year: April 29, 2009
7 authors: E. Hemsing | P. Musumeci | S. Reiche | R. Tikhoplav | Agostino Marinelli | J.B. Rosenzweig | A. Gover
abstract: Microbunching of a relativistic electron beam into a helix is examined analytically and in simulation. Helical microbunching is shown to occur naturally when an e beam interacts resonantly at the harmonics of the combined field of a helical magnetic undulator and an axisymmetric input laser beam. This type of interaction is proposed as a method to generate a strongly prebunched e beam for coherent emission of light with orbital angular momentum at virtually any wavelength. The results from the linear microbunching theory show excellent agreement with three-dimensional numerical simulations.
keywords:
Download | Details | Edit | Delete
title: Observation of coherent terahertz edge radiation from compressed electron beams
format: journal article
publisher: PRSTAB
year: 3 March 2009
9 authors: G. Andonian | A.M. Cook | M. Dunning | E. Hemsing | Gabriel Marcus | A. Murokh | S. Reiche | D. Schiller | J.B. Rosenzweig
abstract: Coherent radiation emitted from a compressed electron bunch as it traverses the sharp edge regions of a magnetic chicane has been investigated at the Brookhaven National Laboratory Accelerator Test Facility. Electron beam measurements using coherent transition radiation interferometry indicate a 100 fs rms bunch accompanied by distinct distortions in energy spectrum due to strong self-fields. These self-fields are manifested in emitted high power THz radiation, which displays signatures of the phenomenon known as coherent edge radiation. Radiation characterization studies undertaken include spectral analysis, far-field intensity distribution, polarization, and dependence on the electron bunch length. The observed aspects of the beam and radiation allow detailed comparisons with start-to-end simulations.
keywords:
Download | Details | Edit | Delete
title: Coherent transition radiation from a helically microbunched electron beam
format: journal article
publisher:
year: 1 May 2009
2 authors: E. Hemsing | J.B. Rosenzweig
abstract: The coherent transition radiation emitted from an electron beam with higher-order spatial microbunching is analyzed. The characteristic angular and phase dependence can be used to identify the dominant bunching structure of such beams, which can be generated during the harmonic interaction in optical klystron modulators and free-electron lasers, and used as tunable sources of coherent light with orbital angular momentum.
keywords:
Download | Details | Edit | Delete
title: DEVELOPMENT OF A 1.5+0.5 CELL PHOTOINJECTOR
format: journal article
publisher: PAC 09 Proceedings
year: 2009
6 authors: B. O'Shea | J.B. Rosenzweig | Luigi Faillace | A. Fukasawa | Joshua Moody | Pietro Musumeci
abstract: We present the development and status of a traditional UCLA/BNL/SLAC style 1.5 cell photoinjector with an additional half cell downstream to aid in longitudinal pulse compression. The work presented includes radio frequency design via SuperFish and HFSS as well as beam dynamics simulation using PARMELA. We investigate longitudinal compression of an electron beam in this extra downstream half cell and show shorter final beam lengths at the cost of transverse beam quality, when compared with traditional 1.6 cell systems.
keywords:
Download | Details | Edit | Delete
title: Novel Radio-Frequency Gun Structures For Ultrafast Relativistic Electron Diffraction
format: journal article
publisher: Microscopy and Microanalysis
year: 2009
7 authors: P. Musumeci | L. Faillace | A. Fukasawa | J.T. Moody | B. O'Shea | J.B. Rosenzweig | C.M. Scoby
abstract: Radio-frequency (RF) photoinjector-based relativistic ultrafast electron diffraction (UED) is a promising new technique that has the potential to probe structural changes at the atomic scale with sub-100 fs temporal resolution in a single shot. We analyze the limitations on the temporal and spatial resolution of this technique considering the operating parameters of a standard 1.6 cell RF gun (which is the RF photoinjector used for the first experimental tests of relativistic UED at Stanford Linear Accelerator Center; University of California, Los Angeles; Brookhaven National Laboratory), and study the possibility of employing novel RF structures to circumvent some of these limits.
keywords:
Download | Details | Edit | Delete
title: Electron Emission Characterization of Mg Photocathode Grown by Pulsed Laser Deposition Within an S-band RF Gun
format: journal article
publisher: Physical Review Special Topics- Accelerators and Beams
year: 2009
7 authors: L. Cultrera | G. Gatti | P. Miglietta | F. Tazzioli | A. Perrone | J.T. Moody | P. Musumeci
abstract: Pulsed laser deposition (PLD) has been proposed several years ago as a suitable technique to deposit a pure Mg film over a radio frequency (rf ) gun Cu backflange in order to obtain a high efficiency photocathode surface for the generation of high brightness electron beams. In this paper we report preliminary experimental results on the emission properties of a PLD grown Mg film within the high electric field gradients of a rf gun showing the effects of the rf conditioning process on the cathode surface. Even though a laser cleaning process should be performed on the sample surface in order to remove contaminated layers, the results presented here are very promising for the realization of a final Mg-based photocathode.
keywords:
Download | Details | Edit | Delete
title: Coherent optical vortices from relativistic electron beams
format: journal article
publisher: Nature Physics
year: 2013
7 authors: E. Hemsing | A. Knyazik | M. Dunning | D. Xiang | A. Marinelli | C. Hast | J.B. Rosenzweig
abstract: Recent advances in the production and control of high-brightness electron beams (e-beams) have enabled a new class of intense light sources based on the free electron laser (FEL) that can examine matter at ångstrom length and femtosecond time scales. The free, or unbound, electrons act as the lasing medium, which provides unique opportunities to exquisitely control the spatial and temporal structure of the emitted light through precision manipulation of the electron distribution. We present an experimental demonstration of light with orbital angular momentum (OAM; ref.) generated from a relativistic e-beam rearranged into an optical scale helix by a laser. With this technique, we show that a Gaussian laser mode can be effectively up-converted to an OAM mode in an FEL using only the e-beam as a mode-converter. Results confirm theoretical predictions and pave the way for the production of coherent OAM light with unprecedented brightness down to hard X-ray wavelengths for wide ranging applications in modern light sources.
keywords:
Download | Details | Edit | Delete
title: Efficient harmonic microbunching in a 7th-order inverse-free-electron laser interaction
format: journal article
publisher: Physical Review Special Topics- Accelerators and Beams
year: 2009
8 authors: S. Ya. Tochitsky | O.B. Williams | P. Musumeci | C. Sung | D.J. Haberberger | A.M. Cook | J.B. Rosenzweig | C. Joshi
abstract: We have shown that a seventh-order inverse-free-electron laser (IFEL) interaction, where the radiation frequency is the seventh harmonic of the fundamental resonant frequency, can microbunch a beam of relativistic electrons inside an undulator. Using coherent transition radiation (CTR) emitted by the bunched 12.3 MeV beam as a diagnostic, strong microbunching of the beam is inferred from the observation of CTR at the first, second, and third harmonics of the seed 10 m radiation. Threedimensional IFEL simulations show that the observed harmonic ratios can be explained only if transverse spatial distribution of the steepened bunched beam is taken into account.
keywords:
Download | Details | Edit | Delete
title: Three dimensional analysis of longitudinal plasma oscillations in a thermal relativistic electron beam
format: journal article
publisher: Physics of Plasmas
year: 2011
3 authors: A. Marinelli | E. Hemsing | J.B. Rosenzweig
abstract: In this paper, we develop a three-dimensional kinetic theory of longitudinal plasma oscillations in a relativistic electron beam. Our analysis includes the effects of betatronmotion, finite emittance, and energy spread as well as edge effects due to the finite size of the beam. The consequences of these effects are shown to be of significant interest, as they give rise to several distinct new phenomena. These include an emittance induced anisotropy between backward and forward propagating plasma waves as well as a beatwave effect between plasma and betatronoscillations caused by the coupling of betatronmotion to the transverse structure of the charge perturbation. The experimental implications of these new results and their relevance to the beam and radiation physics of advanced light sources, such as free-electron lasers, are also discussed.
keywords:
Download | Details | Edit | Delete
title: High brightness electron beam emittance evolution measurements in an rf photoinjector
format: journal article
publisher: Physical Review Special Topics- Accelerators and Beams
year: 2008
48 authors: A. Cianchi | D. Alesini | A. Bacci | M. Bellaveglia | R. Boni | M. Boscolo | M. Castellano | L. Catani | E. Chiadroni | S. Cialdi | A. Clozzo | L. Cultrera | G. Di Pirro | A. Drago | A. Esposito | M. Ferrario | L. Ficcadenti | D. Filippetto | V. Fusco | A. Gallo | G. Gatti | A. Ghigo | L. Giannessi | C. Ligi | M. Mattioli | M. Migliorati | A. Mostacci | P. Musumeci | E. Pace | L. Palumbo | L. Pellegrino | M. Petrarca | M. Preger | M. Quattromini | R. Ricci | C. Ronsivalle | J.B. Rosenzweig | A.R. Rossi | C. Sanelli | L. Serafini | M. Serio | F. Sgamma | B. Spataro | F. Tazzioli | S. Tomassini | C. Vaccarezza | M. Vescovi | and C. Vicario
abstract: The new generation of linac injectors driving free electron lasers in the self-amplified stimulated emission (SASE-FEL) regime requires high brightness electron beams to generate radiation in the wavelength range from UV to x rays. The choice of the injector working point and its matching to the linac structure are the key factors to meet this requirement. An emittance compensation scheme presently applied in several photoinjectors worldwide is known as the ��Ferrario�� working point. In spite of its great importance there was, so far, no direct measurement of the beam parameters, such as emittance, transverse envelope, and energy spread, in the region downstream the rf gun and the solenoid of a photoinjector to validate the effectiveness of this approach. In order to fully characterize the beam dynamics with this scheme, an innovative beam diagnostic device, the emittance meter, consisting of a movable emittance measurement system, has been designed and built. With the emittance meter, measurements of the main beam parameters in both transverse phase spaces can be performed in a wide range of positions downstream the photoinjector. These measurements help in tuning the injector to optimize the working point and provide an important benchmark for the validation of simulation codes. We report the results of these measurements in the SPARC photoinjector and, in particular, the first experimental evidence of the double minimum in the emittance oscillation, which provides the optimized matching to the SPARC linac.
keywords:
Download | Details | Edit | Delete
title: Observation of Narrow-Band Terahertz Coherent Cherenkov Radiation from a Cylindrical Dielectric-Lined Waveguide
format: journal article
publisher:
year: 2009
6 authors: A. M. Cook | R. Tikhoplav | S. Y. Tochitsky | G. Travish | O. B. Williams | J.B. Rosenzweig
abstract: We report experimental observation of narrow-band coherent Cherenkov radiation driven by a subpico- second electron bunch traveling along the axis of a hollow cylindrical dielectric-lined waveguide. For an appropriate choice of dielectric wall thickness, a short-pulse beam current profile excites only the fundamental mode of the structure, producing energetic pulses in the terahertz range. We resent detailed measurements showing a narrow emission spectrum peaked at 367 3 GHz from a 1 cm long fused silica capillary tube with submillimeter transverse dimensions, closely matching predictions. We demonstrate a 100 GHz shift in the emitted central frequency when the tube wall thickness is changed by 50
keywords:
Download | Details | Edit | Delete
title: Longitudinal phase space characterization of the blow-out regime of rf photoinjector operation
format: journal article
publisher:
year: 2009
5 authors: J.T. Moody | P. Musumeci | M. S. Gutierrez | J.B. Rosenzweig | C. M. Scoby
abstract: Using an experimental scheme based on a vertically deflecting rf deflector and a horizontally dispersing dipole, we characterize the longitudinal phase space of the beam in the blow-out regime at the UCLA Pegasus rf photoinjector. Because of the achievement of unprecedented resolution both in time (50 fs) and energy (1.0 keV), we are able to demonstrate some important properties of the beams created in this regime such as extremely low longitudinal emittance, large temporal energy chirp, and the degrading effects of the cathode image charge in the longitudinal phase space which eventually leads to poorer beam quality. All of these results have been found in good agreement with simulations.
keywords:
Download | Details | Edit | Delete
title: Direct Measurement of the Double Emittance Minimum in the Beam Dynamics of the Sparc High-Brightness Photoinjector
format: journal article
publisher: Physical Review Letters
year: 6 December 2007
47 authors: M. Ferrario | D. Alesini | A. Bacci | M. Bellaveglia | R. Boni | M. Boscolo | M. Castellano | L. Catani | E. Chiadroni | S. Cialdi | A. Cianchi | A. Clozza | L. Cultrera | G. Di Pirro | A. Drago | A. Esposito | L. Ficcadenti | D. Filippetto | V. Fusco | A. Gallo | G. Gatti | A. Ghigo | L. Giannessi | C. Ligi | M. Mattioli | M. Migliorati | A. Mostacci | P. Musumeci | E. Pace | L. Palumbo | L. Pellegrino | M. Petrarca | M. Quattromini | R. Ricci | C. Ronsivalle | J.B. Rosenzweig | A.R. Rossi | C. Sanelli | L. Serafini | M. Serio | F. Sgamma | B. Spataro | F. Tazzioli | S. Tomassini | C. Vaccarezza | M. Vescovi | C. Vicario
abstract: In this Letter we report the first experimental observation of the double emittance minimum effect in the beam dynamics of high-brightness electron beam generation by photoinjectors; this effect, as predicted by the theory, is crucial in achieving minimum emittance in photoinjectors aiming at producing electron beams for short wavelength single-pass free electron lasers. The experiment described in this Letter was performed at the SPARC photoinjector site, during the first stage of commissioning of the SPARC project. The experiment was made possible by a newly conceived device, called an emittance meter, which allows a detailed and unprecedented study of the emittance compensation process as the beam propagates along the beam pipe.
keywords:
Download | Details | Edit | Delete
title: Plasma density transition trapping as a possible high-brightness electron beam source
format: journal article
publisher: Physical Review Special Topics- Accelerators and Beams
year: 6 January 2004
3 authors: M.C. Thompson | J.B. Rosenzweig | Suk, H.
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 10^14 A/(mrad)^2. A proof-of-principle transition trapping experiment is planned for the near future. The proposed experiment is described in detail.
keywords:
Download | Details | Edit | Delete
title: Envelope analysis of intense relativistic quasilaminar beams in rf photoinjectors: A theory of emittance compensation
format: journal article
publisher: Physical Review E
year: June 1, 1997
2 authors: Luca Serafini | J.B. Rosenzweig
abstract: In this paper we provide an analytical description for the transverse dynamics of relativistic, space-charge-dominated beams undergoing strong acceleration, such as those typically produced by rf photoinjectors. These beams are chiefly characterized by a fast transition, due to strong acceleration, from the nonrelativistic to the relativistic regime in which the initially strong collective plasma effects are greatly diminished. However, plasma oscillations in the transverse plane are still effective in significantly perturbing the evolution of the transverse phase space distribution, introducing distortions and longitudinal-transverse correlations that cause an increase in the rms transverse emittance of the beam as a whole. The beam envelope evolution is dominated by such effects and not by the thermal emittance, and so the beam flow can be considered quasilaminar. The model adopted is based on the rms envelope equation, for which we find an exact particular analytical solution taking into account the effects of linear space-charge forces, external focusing due to applied as well as ponderomotive RF forces, acceleration, and adiabatic damping, in the limit that the weak nonlaminarity due to the thermal emittance may be neglected. This solution represents a special mode for beam propagation that assures a secularly diminishing normalized rms emittance and it represents the fundamental operating condition of a space-charge-compensated RF photoinjector. The conditions for obtaining emittance compensation in a long, integrated photoinjector, in which the gun and linac sections are joined, as well as in the case of a short gun followed by a drift and a booster linac, are examined.
keywords:
Download | Details | Edit | Delete
title: Experimental Characterization of Superradiance in a Single-Pass High-Gain Laser-Seeded Free-Electron Laser Amplifier
format: journal article
publisher: Physical Review Letters
year: 19 January 2007
9 authors: T. Watanabe | X. J. Wang | J. B. Murphy | J. Rose | Y. Shen | T. Tsang | L. Giannessi | P. Musumeci | S. Reiche
abstract: In this Letter we report the first experimental characterization of superradiance in a single-pass high-gain free-electron laser (FEL) seeded by a 150 femtosecond (FWHM) Ti:sapphire laser. The nonlinear energy gain after an exponential gain regime was observed. We also measured the evolution of the longitudinal phase space in both the exponential and superradiant regimes. The output FEL pulse duration was measured to be as short as 81 fs, a roughly 50% reduction compared to the input seed laser. The temporal distribution of the FEL radiation as predicted by a numerical simulation was experimentally verified for the first time.
keywords:
Download | Details | Edit | Delete
title: Observations of low-aberration plasma lens focusing of relativistic electron beams at the underdense threshold
format: journal article
publisher: Physics of Plasmas
year: 21 July 2010
11 authors: M.C. Thompson | H. Badakov | J.B. Rosenzweig | G. Travish | N. Barov | P. Piot | R. Fliller | G.M. Kazakevich | J. Santucci | J. Li | R. Tikhoplav
abstract: Focusing of a 15 MeV electron bunch by a plasma lens operated at the threshold of the underdense regime has been demonstrated. The strong, 1.7 cm focal length, plasma lens focused both transverse directions simultaneously and reduced the minimum area of the beam spot by a factor of 23. It is shown through analytic analysis and simulation that the observed spherical aberration of this underdense lens, when expressed as the fractional departure of the focusing strength from its linear expectation, is ?K/K=0.08�0.04. This is significantly lower than the minimum theoretical value for the spherical aberration of an overdense plasma lens. Parameter scans showing the dependence of focusing performance on beam charge, as well as time resolved measurements of the focused electron bunch, are reported.
keywords:
Download | Details | Edit | Delete
title: Experimental observation of helical microbunching of a relativistic electron beam
format: journal article
publisher: Applied Physics Letters
year: 2012
8 authors: E. Hemsing | A. Knyazik | F. O'Shea | A. Marinelli | P. Musumeci | O. Williams | S. Tochitsky | J.B. Rosenzweig
abstract: Experimental observation of the microbunching of a relativistic electron beam at the second harmonic interaction frequency of a helical undulator is presented. The microbunching signal is observed from the coherent transition radiation of the electron beam and indicates experimental evidence of a dominantly helical electron beam density distribution. This result is in agreement with theoretical and numerical predictions and provides a proof-of-principle demonstration of proposed schemes designed to generate light with orbital angular momentum in high-gain free-electron lasers.
keywords:
Download | Details | Edit | Delete
title: Gain length fitting formula for free-electron lasers with strong space-charge effects
format: journal article
publisher: Physical Review Accelerators and Beams
year: 2011
3 authors: G. Marcus | E. Hemsing | J.B. Rosenzweig
abstract: We present a power-fit formula, obtained from a variational analysis using three-dimensional free-electron laser theory, for the gain length of a high-gain free-electron laser’s fundamental mode in the presence of diffraction, uncorrelated energy spread, and longitudinal space-charge effects. The approach is inspired by the work of Xie [Nucl. Instrum. Methods Phys. Res., Sect. A 445, 59 (2000)], and provides a useful shortcut for calculating the gain length of the fundamental Gaussian mode of a free-electron laser having strong space-charge effects in the 3D regime. The results derived from analytic theory are in good agreement with detailed numerical particle simulations that also include higher-order space-charge effects, supporting the assumptions made in the theoretical treatment and the variational solutions obtained in the single-mode limit.
keywords:
Download | Details | Edit | Delete
title: Nonlinear Longitudinal Space Charge Oscillations in Relativistic Electron Beams
format: journal article
publisher: Physical Review Letters
year: 6 May 2011
3 authors: P. Musumeci | R.K. Li | A. Marinelli
abstract: In this Letter we study the evolution of an initial periodic modulation in the temporal profile of a relativistic electron beam under the effect of longitudinal space-charge forces. Linear theory predicts a periodic exchange of the modulation between the density and the energy profiles at the beam plasma frequency. For large enough initial modulations, wave breaking occurs after 1=2 period of plasma oscillation leading to the formation of short current spikes. We confirm this effect by direct measurements on a ps-modulated electron beam from an rf photoinjector. These results are useful for the generation of intense electron pulse trains for advanced accelerator applications.
keywords:
Download | Details | Edit | Delete
title: Resonant excitation of coherent Cerenkov radiation in dielectric lined waveguides
format: journal article
publisher:
year: 2011
12 authors: G. Andonian | O. Williams | X. Wei | P. Niknejadi | E. Hemsing | J. B. Rosenzweig | P. Muggli | M. Babzien | M. Fedurin | K. Kusche | R. Malone | V. Yakimenko
abstract: We report the observation of coherent Cerenkov radiation in the terahertz regime emitted by a relativistic electron pulse train passing through a dielectric lined cylindrical waveguide. We describe the beam manipulations and measurements involved in repetitive pulse train creation including comb collimation and nonlinear optics corrections. With this technique, modes beyond the fundamental are selectively excited by use of the appropriate frequency train. The spectral characterization of the structure shows preferential excitation of the fundamental and of a higher longitudinal mode.
keywords:
Download | Details | Edit | Delete
title: Longitudinal profile diagnostic scheme with subfemtosecond resolution for high-brightness electron beams
format: journal article
publisher: PRSTAB
year: 7/13/2011
7 authors: G. Andonian | E. Hemsing | D. Xiang | P. Musumeci | A. Murokh | S. Tochitsky | J.B. Rosenzweig
abstract: High-resolution measurement of the longitudinal profile of a relativistic electron beam is of utmost importance for linac based free-electron lasers and other advanced accelerator facilities that employ ultrashort bunches. In this paper, we investigate a novel scheme to measure ultrashort bunches (subpico- second) with exceptional temporal resolution (hundreds of attoseconds) and dynamic range. The scheme employs two orthogonally oriented deflecting sections. The first imparts a short-wavelength (fast temporal resolution) horizontal angular modulation on the beam, while the second imparts a long-wavelength (slow) angular kick in the vertical dimension. Both modulations are observable on a standard downstream screen in the form of a streaked sinusoidal beam structure. We demonstrate, using scaled variables in a quasi-1D approximation, an expression for the temporal resolution of the scheme and apply it to a proof- of-concept experiment at the UCLA Neptune high-brightness injector facility. The scheme is also investigated for application at the SLAC NLCTA facility, where we show that the subfemtosecond resolution is sufficient to resolve the temporal structure of the beam used in the echo-enabled free-electron laser. We employ beam simulations to verify the effect for typical Neptune and NLCTA parameter sets and demonstrate the feasibility of the concept.
keywords:
Download | Details | Edit | Delete
title: Generating Optical Orbital Angular Momentum in a High-Gain Free-Electron Laser at the First Harmonic
format: journal article
publisher: Physical Review Letters
year: 22 April 2011
3 authors: E. Hemsing | A. Marinelli | J.B. Rosenzweig
abstract: A scheme to generate intense coherent light that carries orbital angular momentum (OAM) at the fundamental wavelength of an x-ray free-electron laser (FEL) is described. The OAM light is emitted as the dominant mode of the system until saturation provided that the helical microbunching imposed on the electron beam is larger than the shot-noise bunching that leads to self-amplified emission. Operating at the fundamental, this scheme is more efficient than alternate schemes that rely on harmonic emission, and can be applied to x-ray FELs without using external optical mode conversion elements.
keywords:
Download | Details | Edit | Delete
title: Self-Amplified Spontaneous Emission Free-Electron Laser with an Energy-Chirped Electron Beam and Undulator Tapering
format: journal article
publisher: Physical Review Letters
year: 8 April 2011
41 authors: L. Giannessi | A. Bacci | M. Bellaveglia | F. Briquez | M. Castellano | E. Chiadroni | A. Cianchi | F. Ciocci | M.E. Couprie | L. Cultrera | G. Dattoli | D. Filippetto | M. Del Franco | G. Di Pirro | M. Ferrario | L. Ficcadenti | F. Frassetto | A. Gallo | G. Gatti | M. Labat | Gabriel Marcus | M. Moreno | A. Mostacci | E. Pace | A. Petralia | V. Petrillo | L. Poletto | M. Quattromini | J.V. Rau | C. Ronsivalle | J.B. Rosenzweig | A.R. Rossi | V. Rossi Albertini | E. Sabia | M. Serluca | S. Spampinati | I. Spassovsky | B. Spataro | V. Surrenti | C. Vaccarezza | C. Vicario
abstract: We report the first experimental implementation of a method based on simultaneous use of an energy chirp in the electron beam and a tapered undulator, for the generation of ultrashort pulses in a self-amplified spontaneous emission mode free-electron laser (SASE FEL). The experiment, performed at the SPARC FEL test facility, demonstrates the possibility of compensating the nominally detrimental effect of the chirp by a proper taper of the undulator gaps. An increase of more than 1 order of magnitude in the pulse energy is observed in comparison to the untapered case, accompanied by FEL spectra where the typical SASE spiking is suppressed.
keywords:
Download | Details | Edit | Delete
title: Multiphoton Photoemission from a Copper Cathode Illuminated by Ultrashort Laser Pulses in an rf Photoinjector
format: journal article
publisher: Physical Review Letters
year: 26 February 2010
12 authors: P. Musumeci | L. Cultrera | M. Ferrario | D. Filippetto | G. Gatti | M.S. Gutierrez | J.T. Moody | N. Moore | J.B. Rosenzweig | C.M. Scoby | G. Travish | C. Vicario
abstract: In this Letter we report on the use of ultrashort infrared laser pulses to generate a copious amount of electrons by a copper cathode in an rf photoinjector. The charge yield verifies the generalized Fowler-Dubridge theory for multiphoton photoemission. The emission is verified to be prompt using a two pulse autocorrelation technique. The thermal emittance associated with the excess kinetic energy from the emission process is comparable with the one measured using frequency tripled uv laser pulses. In the high field of the rf gun, up to 50 pC of charge can be extracted from the cathode using a 80 fs long, 2 J, 800 nm pulse focused to a 140 m rms spot size. Taking into account the efficiency of harmonic conversion, illuminating a cathode directly with ir laser pulses can be the most efficient way to employ the available laser power.
keywords:
Download | Details | Edit | Delete
title: Experimental Demonstration of Emittance Compensation with Velocity Bunching
format: journal article
publisher: Physical Review Letters
year: 5 February 2010
33 authors: M. Ferrario | D. Alesini | A. Bacci | M. Bellaveglia | R. Boni | M. Boscolo | M. Castellano | E. Chiadroni | A. Cianchi | L. Cultrera | G. Di Pirro | L. Ficcadenti | D. Filippetto | V. Fusco | A. Gallo | G. Gatti | L. Giannessi | M. Labat | B. Marchetti | C. Marrelli | M. Migliorati | A. Mostacci | E. Pace | L. Palumbo | M. Quattromini | C. Ronsivalle | A. R. Rossi | J. Rosenzweig | L. Serafini | M. Serluca | B. Spataro | C. Vaccarezza | C. Vicario
abstract: In this Letter we report the first experiments aimed at the simultaneous demonstration of the emittance compensation process and velocity bunching in a high brightness electron source, the SPARC photoinjector in INFN-LNF. While a maximum compression ratio up to a factor 14 has been observed, in a particular case of interest a compression factor of 3, yielding a slice current of 120 A with less than 2 m slice emittance, has been measured. This technique may be crucial in achieving high brightness beams in photoinjectors aiming at optimized performance of short wavelength single-pass free electron lasers or other advanced applications in laser-plasma accelerators.
keywords:
Download | Details | Edit | Delete
title: Electro-optic sampling at 90 degree interaction geometry for time-of-arrival stamping of ultrafast relativistic electron diffraction
format: journal article
publisher: Physical Review Letters
year: 16 February 2010
4 authors: C.M. Scoby | P. Musumeci | J.T. Moody | M.S. Gutierrez
abstract: In this paper we study a new geometry setup for electro-optic sampling (EOS) where the electron beam runs parallel to the h110i face of a ZnTe crystal and the probe laser is perpendicular to it and to the beam path. The simple setup is used to encode the time-of-arrival information of a 3:5 MeV < 10 pC electron bunch on the spatial profile of the laser pulse. The electric field lines inside the dielectric bend at an angle due to a relatively large (n  3) index of refraction of the ZnTe crystal. We found theoretically and experimentally that the EOS signal can be maximized with a proper choice of incoming laser polarization angle. We achieved single-shot nondestructive measurement of the relative time of arrival between the pump and the probe beams thus improving the temporal resolution of ultrafast relativistic electron diffraction experiments.
keywords:
Download | Details | Edit | Delete
title: Short period, high field cryogenic undulator for extreme performance x-ray free electron lasers
format: journal article
publisher: APS
year: 13 July 2010
8 authors: F.H. O'Shea | Gabriel Marcus | J. B. Rosenzweig | Michael Scheer | Johannes Bahrdt | Raphael Weingartner | Andreas Gaupp | Florian Gruner
abstract: Short period, high field undulators can enable short wavelength free electron lasers (FELs) at low beam energy, with decreased gain length, thus allowing much more compact and less costly FEL systems. We describe an ongoing initiative to develop such an undulator based on an approach that utilizes novel cryogenic materials. While this effort was begun in the context of extending the photon energy regime of a laser-plasma accelerator based electron source, we consider here implications of its application to sub-fs scenarios in which more conventional injectors are employed. The use of such low-charge, ultrashort beams, which has recently been proposed as a method of obtaining single-spike performance in x-ray FELs, is seen in simulation to give unprecedented beam brightness. This brightness, when considered in tandem with short wavelength, high field undulators, enables extremely high performance FELs. Two examples discussed in this paper illustrate this point well. The first is the use of the SPARX injector at 2.1 GeV with 1 pC of charge to give 8 GW peak power in a single spike at 6.5 � with a photon beam peak brightness greater than 1035??photons/(s?mm2?mrad2??0.1%??BW), which will also reach LCLS wavelengths on the 5th harmonic. The second is the exploitation of the LCLS injector with 0.25 pC, 150 as pulses to lase at 1.5 � using only 4.5 GeV energy; beyond this possibility, we present start-to-end simulations of lasing at unprecedented short wavelength, 0.15 �, using 13.65 GeV LCLS design energy.
keywords:
Download | Details | Edit | Delete
title: Dielectric Wakefield Acceleration of a Relativistic Electron Beam in a Slab-Symmetric Dielectric Lined Waveguide
format: journal article
publisher: Physical Review Letters
year: 15 June 2012
13 authors: G. Andonian | D. Stratakis | M. Babzien | S. Barber | M. Fedurin | E. Hemsing | K. Kusche | P. Muggli | B. O'Shea | X. Wei | O. Williams | V. Yakimenko | and J.B. Rosenzweig
abstract: We report first evidence of wakefield acceleration of a relativistic electron beam in a dielectric-lined slab-symmetric structure. The high energy tail of a ?60??MeV electron beam was accelerated by ?150??keV in a 2 cm-long, slab-symmetric SiO2 waveguide, with the acceleration or deceleration clearly visible due to the use of a beam with a bifurcated longitudinal distribution that serves to approximate a driver-witness beam pair. This split-bunch distribution is verified by longitudinal reconstruction analysis of the emitted coherent transition radiation. The dielectric waveguide structure is further characterized by spectral analysis of the emitted coherent Cherenkov radiation at THz frequencies, from a single electron bunch, and from a relativistic bunch train with spacing selectively tuned to the second longitudinal mode (TM02). Start-to-end simulation results reproduce aspects of the electron beam bifurcation dynamics, emitted THz radiation properties, and the observation of acceleration in the dielectric-lined, slab-symmetric waveguide.
keywords:
Download | Details | Edit | Delete
title: Time-domain measurement of a self-amplified spontaneous emission free-electron laser with an energy-chirped electron beam and undulator tapering
format: journal article
publisher: Applied Physics Letters
year: 24 Sep 2012
2 authors: Gabriel Marcus | J.B. Rosenzweig
abstract: We report, with an unequivocal time-domain measurement, that an appropriately chosen undulator taper can compensate for an electron beam longitudinal energy-chirp in a free-electron laser amplifier, leading to the generation of single-spike radiation close to the Fourier limit. The measurements were taken using the frequency-resolved optical gating technique by employing an advanced transient-grating diagnostic geometry. The reconstructed longitudinal radiation characteristics are compared in detail to prediction from time-dependent three-dimensional simulations.
keywords:
Download | Details | Edit | Delete
title: Generation of Coherent Broadband Photon Pulses with a Cascaded Longitudinal Space-Charge Amplifier
format: journal article
publisher: Physical Review Letters
year: 2013
9 authors: A. Marinelli | E. Hemsing | M. Dunning | D. Xiang | S. Weathersby | F. O'Shea | I. Gadjev | C. Hast | J.B. Rosenzweig
abstract: The longitudinal space-charge amplifier has been recently proposed by Schneidmiller and Yurkov as an alternative to the free-electron laser instability for the generation of intense broadband radiation pulses [Phys. Rev. ST Accel. Beams 13, 110701 (2010)]. In this Letter, we report on the experimental demonstration of a cascaded longitudinal space-charge amplifier at optical wavelengths. Although seeded by electron beam shot noise, the strong compression of the electron beam along the three amplification stages leads to emission of coherent undulator radiation pulses exhibiting a single spectral spike and a single transverse mode. The on-axis gain is estimated to exceed 4 orders of magnitude with respect to spontaneous emission.
keywords:
Download | Details | Edit | Delete
title: Echo-Enabled X-Ray Vortex Generation
format: journal article
publisher: Physical Review Letters
year: 2012
2 authors: E. Hemsing | A. Marinelli
abstract: A technique to generate high-brightness electromagnetic vortices with tunable topological charge at extreme ultraviolet and x-ray wavelengths is described. Based on a modified version of echo-enabled harmonic generation for free-electron lasers, the technique uses two lasers and two chicanes to produce high-harmonic microbunching of a relativistic electron beam with a corkscrew distribution that matches the instantaneous helical phase structure of the x-ray vortex. The strongly correlated electron distribution emerges from an efficient three-dimensional recoherence effect in the echo-enabled harmonic generation transport line and can emit fully coherent vortices in a downstream radiator for access to new research in x-ray science.
keywords:
Download | Details | Edit | Delete
title: Single-Shot Coherent Diffraction Imaging of Microbunched Relativistic Electron Beams for Free-Electron Laser Applications
format: journal article
publisher: Physical Review Letters
year: March 2013
10 authors: A. Marinelli | M. Dunning | S. Weathersby | E. Hemsing | D. Xiang | G. Andonian | F.H. O'Shea | Jianwei Miao | C. Hast | J. B. Rosenzweig
abstract: With the advent of coherent x rays provided by the x-ray free-electron laser (FEL), strong interest has been kindled in sophisticated diffraction imaging techniques. In this Letter, we exploit such techniques for the diagnosis of the density distribution of the intense electron beams typically utilized in an x-ray FEL itself. We have implemented this method by analyzing the far-field coherent transition radiation emitted by an inverse-FEL microbunched electron beam. This analysis utilizes an oversampling phase retrieval method on the transition radiation angular spectrum to reconstruct the transverse spatial distribution of the electron beam. This application of diffraction imaging represents a significant advance in electron beam physics, having critical applications to the diagnosis of high-brightness beams, as well as the collective microbunching instabilities afflicting these systems.
keywords:
Download | Details | Edit | Delete
title: Observation of emission process in hydrogen-like nitrogen Z-pinch discharge with time integrated soft X-ray spectrum pinhole image
format: journal article
publisher: Physics of Plasmas
year: February 2013
15 authors: Y. Sakai | J. Rosenzweig | H. Kumai | Y. Nakanishi | Y. Ishizuka | S. Takahashi | T. Komatsu | Y. Xiao | H. Bin | Z. Quishi | Y. Hayashi | I. Song | T. Kawamura | M. Watanabe | E. Hotta
abstract: The emission spectra of hydrogen-like nitrogen Balmer at the wavelength of 13.4 nm in capillary Z-pinch discharge plasma are experimentally examined. Ionization to fully strip nitrogen at the pinch maximum, and subsequent rapid expansion cooling are required to establish the population inversion between the principal quantum number of n¼2 and n¼3. The ionization and recombination processes with estimated plasma parameters are evaluated by utilizing a time integrated spectrum pinhole image containing radial spatial information. A cylindrical capillary plasma is pinched by a triangular pulsed current with peak amplitude of 50 kA and pulse width of 50 ns.
keywords:
Download | Details | Edit | Delete
title: Using the Relativistic Two-Stream Instability for the Generation of Soft-X-Ray Attosecond Radiation Pulses
format: journal article
publisher: Physical Review Letters
year: February 2013
3 authors: A. Marinelli | E. Hemsing | J. B. Rosenzweig
abstract: In this Letter we discuss a novel method for generating ultrashort radiation pulses using a broadband two-stream instability in an intense relativistic electron beam. This method relies on an electron beam having two distinct two-energy bands. The use of this new high brightness electron beam scenario, in combination with ultrashort soft x-ray pulses from high harmonic generation in gas, allows the production of high power attosecond pulses for ultrafast pump and probe experiments.
keywords:
Download | Details | Edit | Delete
title: Stable Charged-Particle Acceleration and Focusing in a Laser Accelerator Using Spatial Harmonics
format: journal article
publisher: Physical Review Letters
year: October 2012
4 authors: B. Naranjo | A. Valloni | S. Putterman | J. B. Rosenzweig
abstract: Regarding the laser-driven acceleration of charged particles in photonic systems, a central unmet challenge is the achievement of simultaneous transverse and longitudinal stability at nonultrarelativistic energies. At such energies, Earnshaw’s theorem [S. Earnshaw, Trans. Cambridge Philos. Soc. 7, 97 (1842)] indicates that a synchronous accelerating wave gives a defocusing effect. We present a scheme in which particles are accelerated by interaction with a resonant spatial harmonic and are focused by strong ponderomotive interaction with nonresonant spatial harmonics. We show that this scheme exhibits net transverse focusing and longitudinal stability, and we discuss its use in a compact laser accelerator.
keywords:
Download | Details | Edit | Delete
title: Three dimensional analysis of longitudinal plasma oscillations in a thermal relativistic electron beam: Application to an initial value problem
format: journal article
publisher: Physics of Plasmas
year: 2012
3 authors: A. Marinelli | E. Hemsing | J.B. Rosenzweig
abstract: In this paper, we study the initial value problem of longitudinal plasma oscillations in a relativistic electron beam. Our analysis is based on the formalism developed in Marinelli et al. [Phys. Plasmas 18, 103105 (2011)]. We study the evolution of an arbitrary six-dimensional phase-space perturbation under the effect of longitudinal space-charge forces, with the inclusion of three-dimensional effects due to the finite size of the beam, transverse betatron motion, and longitudinal thermal motion induced by both energy-spread and transverse emittance. We expand the phase-space perturbation in a series of eigenmodes of a Schrödinger-like equation, corresponding to a set of propagating space-charge waves. We develop a general formalism, which we use to find explicit expressions for the evolution of an initial perturbation coupled to the fundamental plasma eigenmode. This work has important applications in the theory of space-charge instabilities in high brightness electron beams and control of shot-noise in seeded free-electron lasers. We discuss the application of the present theory to a specific experimental scenario corresponding to a shot-noise suppression scheme at optical wavelengths.
keywords:
Download | Details | Edit | Delete
title: Harmonic radiation of a relativistic nonlinear inverse Compton scattering using two laser wavelengths
format: journal article
publisher:
year: 2011
9 authors: Y. Sakai | O. Williams | G. Andonian | A. Fukasawa | E. Hemsing | A. Marinelli | S. Barber | F.H. O'Shea | J.B. Rosenzweig
abstract: The use of two different wavelength lasers in the nonlinear regime of the inverse Compton scattering interaction is proposed in order to provide a new strategy for controlling scattered photon energy distributions in the x-ray to γ-ray spectral region. In this nonlinear interaction, the component of the relativistic electron’s trajectory driven by a longer-wavelength laser with the normalized vector potential aL∼1 is a large oscillatory figure-8; in the proposed scenario a rapid small-amplitude oscillation induced by a shorter-wavelength laser is superimposed upon this figure-8. Thus, the electron’s momentum is mainly supplied from longer-wavelength laser, while the high-frequency part of the acceleration is given by shorter-wavelength laser. In this way, the harmonics radiated at high frequency from the oscillating electron can be strongly modified by the nonlinear motion initiated by the low frequency, large aL laser resulting in the generation of the harmonics with the photon energy of 4γ2h̵(ωL,short+nωL,long). In this paper, the electron’s kinetics in the two-wavelength laser field and the concomitant emitted radiation spectrum are examined, with numerical illustrations based on a classical Lienard-Wiechert potential formalism provided.
keywords:
Download | Details | Edit | Delete
title: Observation of redshifting and harmonic radiation in inverse Compton scattering
format: journal article
publisher:
year: 2015
21 authors: Y. Sakai | I. Pogorelsky | O. Williams | F.H. O'Shea | S. Barber | I. Gadjev | J. Duris | P. Musumeci | M. Fedurin | A. Korostyshevsky | B. Malone | C. Swinson | G. Stenby | K. Kusche | M. Babzien | M. Montemagno | P. Jacob | Z. Zhong | M. Polyanskiy | V. Yakimenko | J.B. Rosenzweig
abstract: Inverse Compton scattering of laser photons by ultrarelativistic electron beam provides polarized x- to γ-ray pulses due to the Doppler blueshifting. Nonlinear electrodynamics in the relativistically intense linearly polarized laser field changes the radiation kinetics established during the Compton interaction. These are due to the induced figure-8 motion, which introduces an overall redshift in the radiation spectrum, with the concomitant emission of higher order harmonics. To experimentally analyze the strong field physics associated with the nonlinear electron-laser interaction, clear modifications to the angular and wavelength distributions of x rays are observed. The relativistic photon wave field is provided by the ps CO2 laser of peak normalized vector potential of 0.5
keywords:
Download | Details | Edit | Delete
title: Experimental demonstration of fresh bunch self-seeding in an X-ray free electron laser
format: journal article
publisher: Applied Physics Letters
year: 2017
7 authors: C. Emma | A. Lutman | M.W. Guetg | J. Krzywinski | A. Marinelli | J. Wu | C. Pellegrini
abstract: We report the generation of ultrahigh brightness X-ray pulses using the Fresh Bunch Self-Seeding (FBSS) method in an X-ray Free Electron Laser (XFEL). The FBSS method uses two different electron slices or bunches, one to generate the seed and the other to amplify it after the monochro- mator. This method circumvents the trade-off between the seed power and electron slice energy spread, which limits the efficiency of regular self-seeded FELs. The experiment, the performance of which is limited by existing hardware, shows FBSS feasibility, generating 5.5 keV photon pulses which are 9 fs long and of 7.3 10 5 bandwidth and 50 GW power. FBSS performance is com- pared with Self Amplified Spontaneous Emission/self-seeding performance, measuring a brightness increase of twelve/two times, respectively. In an optimized XFEL, FBSS can increase the peak power a hundred times more than state-of-the-art to multi-TW, opening new research areas for nonlinear science and single molecule imaging.
keywords:
Download | Details | Edit | Delete