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G. Andonian

First Name: Gerard

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Last Name: Andonian

Full Name: G. Andonian

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35 papers
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.
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title: Beyond Injection: Trojan Horse Underdense Photocathode Plasma Wakefield Acceleration
format: conference proceeding
conference: AAC 2012 15th
year: 2012
18 authors: B. Hidding | J.B. Rosenzweig | Y.Xi | B. O'Shea | G. Andonian | D. Schiller | S. Barber | O. Williams | G. Pretzler | T. Königstein | F. Kleeschulte | M.J. Hogan | M. Litos | S. Corde | W.W. White | P. Muggli | D.L. Bruhwiler | K. Lotov
abstract: An overview on the underlying principles of the hybrid plasma wakefield acceleration scheme dubbed ”Trojan Horse” acceleration is given. The concept is based on laser-controlled release of electrons directly into a particle-beam- driven plasma blowout, paving the way for controlled, shapeable electron bunches with ultralow emittance and ultrahigh brightness. Combining the virtues of a low-ionization-threshold underdense photocathode with the GV/m-scale electric fields of a practically dephasing-free beam-driven plasma blowout, this constitutes a 4th generation electron acceleration scheme. It is applicable as a beam brightness transformer for electron bunches from LWFA and PWFA systems alike. At FACET, the proof-of-concept experiment ”E-210: Trojan Horse Plasma Wakefield Acceleration” has recently been approved and is in preparation. At the same time, various LWFA facilities are currently considered to host experiments aiming at stabilizing and boosting the electron bunch output quality via a trojan horse afterburner stage. Since normalized emittance and brightness can be improved by many orders of magnitude, the scheme is an ideal candidate for light sources such as free-electron-lasers and those based on Thomson scattering and betatron radiation alike.
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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.
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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.
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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.
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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.
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title: Breaking the Attosecond, Angstrom and TV/m Field Barriers with Ultrafast Electron Beams
format: conference proceeding
conference: AAC 2010 14th
year: 2010
17 authors: J.B. Rosenzweig | G. Andonian | P. Bucksbaum | A. Fukasawa | M. Ferrario | M. Hogan | E. Hemsing | P. Krejcik | G. Marcus | A. Marinelli | P. Muggli | P. Musumeci | B. O'Shea | F. O'Shea | C. Pellegrini | D. Schiller | G. Travish
abstract: Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This scheme uses very low charge beams, which may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the Stanford X-ray FEL (LCLS, first of its kind, built with essential UCLA leadership) have produced ~2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments at UCLA in cryogenic undulator technology, to create compact accelerator/undulator systems that can lase below 0.15 Å, or be used to permit 1.5 Å operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications. We discuss the experimental issues associated with this initiative.
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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.
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title: A real-time bunch length terahertz interferometer
format: conference proceeding
conference: EPAC 2008
year: 2008
5 authors: G. Andonian | S. Boucher | P. Frigola | A. Murokh | G. Travish
abstract: The recent development of advanced photoinjectors and next generation light sources guides the progression towards high-current, ultra-short beams. The measurement of these short pulses, with sub-picosecond resolution, is essential for successful beam operation and optimization. This paper describes the development of a real-time, shotto-shot bunch length diagnostic utilizing a novel coherent terahertz radiation autocorrelation technique. The proposed diagnostic is called the real-time interferometer (RTI).
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title: Chicane Radiation Measurements with a Compressed Electron Beam at the BNL ATF
format: conference proceeding
conference: PAC 2007
year: 2007
12 authors: G. Andonian | R. Agustsson | A.M. Cook | M. Dunning | E. Hemsing | A. Murokh | Sven Reiche | J.B. Rosenzweig | M. Babzien | K. Kusche | R. Malone | V. Yakimenko
abstract: The radiation emitted from a chicane compressor has been studied at the Brookhaven National Laboratory (BNL) Accelerator Test Facility (ATF). Coherent edge radiation (CER) is emitted from a compressed electron beam as it traverses sharp edge regions of a magnet. The compression is accompanied by strong self-fields, which are manifested as distortions in the momentum space called beam bifurcation. Recent measurements indicate that the bunch length is approximately 100 fs rms. The emitted THz chicane radiation displays strong signatures of CER. This paper reports on the experimental characterization and subsequent analysis of the chicane radiation measurements at the BNL ATF with a discussion of diagnostics development and implementation. The characterization includes spectral analysis, far-field intensity distribution, and polarization effects. Experimental data is benchmarked to a custom developed start-to-end simulation suite.
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title: Characterization of Orbital Angular Momentum Modes in FEL Radiation
format: conference proceeding
conference: PAC 2007
year: 2007
5 authors: E. Hemsing | G. Andonian | J.B. Rosenzweig | M. Babzien | V. Yakimenko
abstract: It is well known that Gaussian modes of paraxial light can possess orbital angular momentum (OAM) as a result of a exp( ?il?) azimuthal angular dependence[1]. Recent experiments on the VISA free-electron laser operating as self-amplified spontaneous amplifier (SASE) at ?=840 nm have produced transverse electromagnetic radiation inten- sity patterns that suggest the presence of one or more OAM modes. Though the intensity profiles from VISA are com- pelling, work remains to discern the phase structure since OAM modes are revealed by a characteristic helical phase dependence, with a pathological singularity on axis. Here we discuss current efforts to characterize the mode content of the VISA FEL through experiments, theoretical mod- els, and simulations. Possible methods to generate OAM modes in situ are discussed.
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title: Seeded VISA: A 1064 nm Laser-Seeded FEL Amplifier at the BNL ATF
format: conference proceeding
conference: PAC 2007
year: 2007
7 authors: M. Dunning | G. Andonian | E. Hemsing | S. Reiche | J.B. Rosenzweig | M. Babzien | V. Yakimenko
abstract: An experimental study of a seeded Free Electron Laser (FEL) using the VISA undulator and a Nd:YAG seed laser will be performed at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory. The study is motivated by the demand for a short Rayleigh length FEL amplifier at 1 micron to allow for high power transmission with min- imal damage of transport optics. Planned measurements include transverse and longitudinal coherence, angular dis- tribution, and wavelength spectrum of the FEL radiation. The effects of detuning the electron beam energy will be studied, with an emphasis on control of the radiation emis- sion angles and increase of the amplifier efficiency. Results of start-to-end simulations are also presented.
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title: Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam through a Compressor Chicane
format: conference proceeding
conference: PAC 2007
year: 2007
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 60MeV, 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 12MeV.
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title: Beam compression experiments using the UCLA/ATF compressor
format: conference proceeding
conference: AAC 2006 12th
year: 2006
13 authors: D. Schiller | E. Hemsing | J.B. Rosenzweig | M.P. Dunning | G. Andonian | A. Murokh | A.M. Cook | Sven Reiche | M. Babzien | K. Kusche | V. Yakimenko | L. Palumbo | C. Vicario
abstract: We review recent experimental results from the BNL ATF using the compressor built by UCLA. The measurements discussed include: first observation of short wavelength coherent edge radiation angular/wavelength spectrum and spectrum, sub-100 fsec pulse-length coherent transition autocorrelation measurements, and longitudinal and transverse phase space distortions. Extension of these measurements, as well as those which can be made possible by a new X-band traveling wave deflector being developed in an industrial collaboration, are examined.
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title: Magnetic Chicane Radiation Studies at the BNL ATF
format: conference proceeding
conference: FEL 2006 28th
year: 2006
11 authors: M.Dunning | G. Andonian | A.M. Cook | E. Hemsing | A.Murokh | Sven Reiche | J.B. Rosenzweig | D. Schiller | M. BABZIEN | K. Kusche | V. Yakimenko
abstract: Radiation emitted by relativistic electrons traversing the magnetic field gradients of a chicane bunch compressor has been studied in an attempt to characterize coherent edge radiation (CER). The studies performed at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory (BNL) include frequency spectrum, angular distribution, and polarization measurements. A reconstruction of the longitudinal charge profile from the measured spectrum shows that the bunch has been compressed to approximately 30 ?m FWHM, with a peak current exceeding 1.5 kA. Measurements of radiation from the short pulses are compared to predictions from QUINDI, a new simulation code developed at UCLA to model the radiation.
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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.
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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.
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title: Observation of Coherent Edge Radiation Emitted by a 100 Femtosecond Compressed Electron Beam
format: conference proceeding
conference: ICFA Workshop on Physics and Applications of High Brightness Electron Beams
year: 2006
14 authors: G. Andonian | M. Dunning | E. Hemsing | J.B. Rosenzweig | A. M. Cook | A. Murokh | S. Reiche | M. Babzien | I. Ben-Zvi | K. Kusche | V. Yakimenko | D. Alesini | L. Palumbo | C. Vicario
abstract: A chicane compressor developed by UCLA for the production of ultra-short, 60 MeV electron beams at the Brookhaven National Laboratory Accelerator Test Facility has been commissioned, and initial beam physics experiments have been performed. These measurements have established the compression of electron beams to the 100 femtosecond (1 kA peak current) regime, via coherent transition radiation (CTR) based measurements. Investigations of coherent edge radiation (CER) include signatures that differentiate it from coherent synchrotron radiation (CSR), such as polarization and far-field angular distribution. Additionally, the radiation wavelength spectrum is determined from autocorrelation measurements. Radiation properties are compared to detailed start-to-end simulations derived from PARMELA and QUINDI (a Lienard-Wiechert code developed at UCLA). Plans for future experiments which further explore the observed wavelength spectra are presented.
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title: Simulations, Diagnostics and Recent Results of the VISA II Experiment
format: conference proceeding
conference: FEL 2005 27th
year: August 2005
17 authors: G. Andonian | A. Murokh | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | G. Travish | M. Babzien | I. Ben-Zvi | V. Litvinenko | V. Yakimenko | I. Boscolo | S. Cialdi | A. Flacco | M. Ferrario | L. Palumbo | C. Vicario | J. Huang
abstract: The VISA II experiment entails the use of a chirped electron beam to drive a high gain SASE FEL. Sextupoles are implemented to correct the longitudinal aberrations affecting the high energy spread chirped beam during transport to the undulator. The output radiation is diagnosed with a modified frequency resolved optical gating (FROG) technique. The double differential energy spectrum is measured with a pair of slits and a set of gratings. In this paper, we report on start-to-end simulations, radiation diagnostics, as well as initial experimental results. Technical considerations for future experimental methods are also addressed.
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title: Recent Results from and Future Plans for the VISA II SASE FEL
format: conference proceeding
conference: PAC 2005
year: 2005
19 authors: G. Andonian | R. Agustsson | P. Frigola | A. Murokh | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | G. Travish | M. BABZIEN | I. Ben-Zvi | V. Litvinenko | V. Yakimenko | I. Boscolo | S. Cialdi | A. Flacco | M. Ferrario | L. Palumbo | C. Vicario | J. Huang
abstract: The VISA II (Visible to Infrared SASE Amplifier) project, a consequent experiment to the succesful VISA enterprise, entails the use of a chirped electron beam to drive a high gain SASE FEL. The resulting ultra-short pulses will be characterized using an advanced FROG (Frequency Resolved Optical Gating) technique, as well as a double differential spectrum (angle/wavelength) diagnostic. Implementation of sextupole corrections to the longitudinal aberrations affecting the high energy-spread chirped beam during transport to the VISA undulator is studied. Start-end simulations, including radiation diagnostics, are discussed. Initial experimental results involving a highly chirped beam transported without sextupole corrections, the resulting high gain lasing, and computational analysis are briefly reported.
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title: Experimental and Analytical Study of a High Gain Self Amplified Spontaneous Emission Free Electron Laser Operating in a Large Spectral Bandwidth Regime
format: thesis
year: 2005
1 author: Gerard Andonian
abstract: The drive to create and measure ultra-short pulses in the x-ray regime advances the ongoing development of free electron lasers (FEL). Several proposed schemes, to shorten the pulse length of the radiation, involve driving the FEL with a chirped (linear longitudinal phase space correlation) electron beam in the self amplified spontaneous emission (SASE) mode. This dissertation examines the experiments conducted under such conditions, canvassing analytical and numerical studies of beam dynamics and radiation properties, experimental observations, and descriptions of the development of novel diagnostics. The VISA (Visible-Infrared SASE Amplifier) program has achieved saturation at 840 nm within a 4 m long undulator. A novel bunch compression mechanism during transport was discovered and ultimately responsible for the high peak current required to drive the FEL. Start-to-end simulations, detailing the dynamics from electron beam inception at the photocathode to the FEL radiation properties at the undulator, were successfully benchmarked to observable data.
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title: Observation of Anomalously Large Spectral Bandwidth in a High Gain Self-amplified Spontaneous Emission Free-Electron Laser
format: preprint
year: 2005
14 authors: G. Andonian | A. Murokh | J.B. Rosenzweig | R. Agustsson | M. Babzien | I. Ben-Zvi | Pedro Frigola | J. Huang | L. Palumbo | C. Pellegrini | Sven Reiche | G. Travish | C. Vicario | V. Yakimenko
abstract: Observation of ultra-wide bandwidth, up to a full width of 15%, 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 (~ 1.7%) emitted from the accelerator. Because of non-linear pulse compression during beam transport, a short, high current pulse with strong mismatch errors is injected into the undulator, bringing about high FEL gain. Start-end simulations reproduce key features of the measured results, and provide insight into mechanisms, such as angular spread in both emitted photon and electron trajectory distributions, which yield novel features in the radiation spectrum.
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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.
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title: Recent Results from and Future Plans for the VISA II SASE FEL
format: preprint
year: 2005
19 authors: G. Andonian | R. Agustsson | Pedro Frigola | A. Murokh | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | G. Travish | M. BABZIEN | I. Ben-Zvi | V. Litvinenko | V. Yakimenko | I. Boscolo | S. Cialdi | A. Flacco | M. Ferrario | L. Palumbo | C. Vicario | J. Huang
abstract: The VISA II (Visible to Infrared SASE Amplifier) project, a consequent experiment to the succesful VISA enterprise, entails the use of a chirped electron beam to drive a high gain SASE FEL. The resulting ultra-short pulses will be characterized using an advanced FROG (Frequency Resolved Optical Gating)technique, as well as a double differential spectrum (angle/wavelength) diagnostic. Implementation of sextupole corrections to the longitudinal aberrations affecting the high energy-spread chirped beam during transport to the VISA undulator is studied. Start-end simulations, including radiation diagnostics, are discussed. Initial experimental results involving a highly chirped beam transported without sextupole corrections, the resulting high gain lasing, and computational analysis are briefly reported.
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title: Experimental Characterization of 4-D Transverse Phase-Space of a Compressed Beam
format: conference proceeding
conference: PAC 2005
year: 2005
8 authors: F. Zhou | R. Agustsson | G. Andonian | D. Cline | A. Murokh | J.B. Rosenzweig | I. Ben-Zvi | V. Yakimenko
abstract: Coherent synchrotron radiation (CSR) may severely deteriorate electron beam qualities, such as distortion of energy spectrum and transverse phase-space in the bending plane when the beam transports through a magnetic bunch compressor. Recently some laboratories conducted some investigations on CSR effects but mostly focused on the measurements of emittance growth and energy spread and or/ energy loss. However, these parameters may not completely represent a fully compressed beam because its phase spaces may be severely distorted and thus some information may be lost if only these basic parameters are used. It is preferred to reconstruct six-dimensional phase spaces of a compressed beam using tomographic techniques in order to fully understand a beam affected by CSR effects. This report will focus on the four-dimensional transverse phase-space tomographic measurements for a fully compressed beam at 60-MeV energy. Its experimental characterizations at different beam parameters are preliminarily examined.
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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.
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title: VISA IB: Ultra-High Bandwidth, High Gain SASE FEL
format: conference proceeding
conference: FEL 2004 26th
year: 2004
15 authors: G. Andonian | A. Murokh | R. Agustsson | C. Pellegrini | S. Reiche | J.B. Rosenzweig | G. Travish | M. Babzien | I. Ben-Zvi | J. Y. Huang | V. Litvinenko | V. Yakimenko | M. Ferrario | L. Palumbo | C. Vicario
abstract: We report the results of a high energy spread SASE FEL experiment, the intermediary experiment linking the VISA I and VISA II projects. A highly chirped beam (1.7 %) was transported, without corrections of longitudinal aberrations in the ATF dogleg, and injected into the VISA undulator. The ouput radiation displayed an uncharacteristicly large bandwidth (12 %) with extremely stable lasing and mea- sured energy of about 2 ?J . Start-to-end simulations re- produced key features of the experiment and provided an insight into the michanisms giving rise to such a high band- width. These analyses have important implications on the VISA II experiment.
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title: Design and Operation of Pegasus Thermionic Cathode
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: P. Frigola | G. Andonian | Sven Reiche | J.B. Rosenzweig | S. Telfer | G. Travish
abstract: A new thermionic cathode has been developed and installed for use on The PEGASUS plane wave transformer injector. The novel design of the LaB6 cathode allows for thermionic emission as well as photoinjector operation. Test stand measurements as well as in situ operational experience are reported.
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title: Design and Status of the VISA II Experiment
format: conference proceeding
conference: PAC 2003
year: 2003
12 authors: G.Andonian | R.Agustsson | A. Murokh | C.Pellegrini | Sven Reiche | J.B. Rosenzweig | G. Travish | M. BABZIEN | I. Ben-Zvi | V. Yakimenko | L. Palumbo | C. VICARIO
abstract: VISA II is the follow-up project to the successful Visible to Infrared SASE Amplifier (VISA) experiment at the Accelerator Test Facility (ATF) in Brookhaven National Lab (BNL). This paper will report the motivation for and status of the two main experiments associated with the VISA II program. One goal of VISA II is to perform an experimental study of the physics of a chirped beam SASE FEL at the upgraded facilities of the ATF. This requires a linearization of the transport line to preserve energy chirping of the electron beam at injection. The other planned project is a strong bunch compression experiment, where the electron bunch is compressed in the chicane, and the dispersive beamline transport, allowing studies of deep saturation.
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title: The UCLA Pegasus Plane-Wave Transformer Photoinjector
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: G. Travish | G. Andonian | P. Frigola | Sven Reiche | J.B. Rosenzweig | and S. Telfer
abstract: A photoinjector based on a multicell plane wave transformer accelerating structure has been commissioned at the UCLA Department of Physics' Pegasus Laboratory. Design and construction of the novel structure have been previously reported [J. Rosenzweig, et al. PAC Proceedings 1997], and recent operation with a thermionic cathode is being presented at this conference [P. Frigola, et al. these proceedings]. This paper describes the planned operation of the PWT gun as a photoinjector, including design and construction details of the drive laser. Progress to date and future plans are discussed.
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title: Status of the UCLA PEGASUS Laboratory
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: G. Andonian | P. Frigola | Sven Reiche | J.B. Rosenzweig | S. Telfer | G. Travish
abstract: The PEGASUS laboratory is a versatile radiation facility dedicated to the advancement of novel concepts in beam physics. The installation of a new LaB$_6$ cathode will allow for both thermionic emission and photoinjection operation. The PEGASUS plane wave transformer injector has been conditioned to 20 MW of RF power. Recent operations show a 15 MeV dark current beam that will be used for beam radiation studies. An upgrade to the drive laser system has been explored and will be realized shortly. This paper will describe and report the status of the various subsystems of the PEGASUS laboratory and outline the experiments underway, such as innovative beam instrumentation, surface effects in optical transition radiation, Thomson scattering, and waveguide SASE FEL.
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title: The FEL Program at the PEGASUS Injector
format: conference proceeding
conference: PAC 2003
year: 2003
6 authors: Sven Reiche | G. Andonian | P. Frigola | J.B. Rosenzweig | S. Telfer | and G. Travish
abstract: The PEGASUS photo injector at UCLA can produce a photo electrons beam with a normalized emittance of 2 mm mrad at an energy of 12-15 MeV, capable of driving a Free-Electron Laser in the mid IR regime. The FEL program, associated with the PEGASUS injector and presented here, is based on a Self-Amplifying Spontaneous Emission (SASE) FEL. The studies focus on increasing the efficiency of an FEL by novel undulator design and compensation of diffraction effects, using waveguides of millimeter size. In this presentation we also discuss the possibility of the PEGASUS FEL as a THz user facility.
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title: Status of the UCLA PEGASUS Injector Laboratory
format: conference proceeding
conference: FEL 2002 24th
year: 2003
6 authors: G. Andonian | P. Frigola | Sven Reiche | J.B. Rosenzweig | S. Telfer | and G. Travish
abstract: The PEGASUS plane wave transformer injector has been conditioned to 20 MW of RF power. Initial operations show a 15 MeV dark current beam that will be used for beam radiation studies. The design of a new LaB_6 cathode will allow for both thermionic emission and photoinjection operation. Experiments currently planned include novel beam instrumentation, surface effects in optical transition radiation, and waveguide SASE FEL.
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title: Commissioning of the UCLA PEGASUS Photoinjector Laboratory
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: S. Telfer | Sven Reiche | J.B. Rosenzweig | Pedro Frigola | G. Andonian
abstract: The PEGASUS Photoinjector has been commissioned at UCLA. The Plane Wave Transformer Photoinjector provides a high-brightness 17 MeV beam that will be used for numerous beam-radiation studies. Some of these will include SASE FEL, transition radiation from non-standard surfaces, and monochromatic x-ray production via PXR and Thompson scattering.
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title: UCLA PBPL Safety Interlock System Description and Operation Manual
format: tech note
year: 1996
1 author: G. Andonian
abstract: http://pbpl.physics.ucla.edu/Research/Facilities/_PEGASUS/Tech_Notes/Pegasus_Safety_Interlock_System/
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