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S. Reiche

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98 papers
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.
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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: Updates to QUINDI
format: conference proceeding
conference: PAC 2009
year: 2009
2 authors: D. Schiller | S. Reiche
abstract: QUINDI has been developed to address the numerical challenge of calculating the radiation spectra from electron bunches in bending magnet systems. Since the introduction of QUINDI, many improvements and features have been added. QUINDI now supports a 3D model for bending magnets which includes fringing fields. A more modular approach has been achieved which allows better interoperability with other tracking and radiation codes. There have been many updates to the electric field calculation and spectrum processing, as well as to the post-processor, SpecGUI.
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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.
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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.
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title: Single spike operation in SPARC SASE-FEL
format: conference proceeding
conference: EPAC 2008
year: 2008
16 authors: I. Boscolo | F. Castelli | S. Cialdi | V. Petrillo | A. Bacci | L. Serafini | R. Bonifacio | M. Boscolo | M. Ferrario | C. Vaccarezza | L. Giannessi | C. ROnsivalle | L. Palumbo | M. Serluca | J.B. Rosenzweig | S. Reiche
abstract: The single spike operation regime has been analyzed in the case of the SPARC injector and freeelectron-laser. Four different beams at 50 pC are studied, with different production condition and performance.
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title: SPUR: A new code for the calculation of synchrotron radiation from very long undulator systems
format: conference proceeding
conference: EPAC 2008
year: 2008
3 authors: N.C. Ryder | S. Reiche | D.J. Scott
abstract: The accurate calculation of synchrotron radiation from an undulator is a common problem and numerous codes have been developed that describe the radiation from analytic and measured undulator fields. However, for very long undulator systems there is not a suitable code that can handle the amount of data in a convenient manner and which runs in a practically realisable time limit. The development of a new code, SPontaneous Undulator Radiation (SPUR) [1], is presented which computes the spontaneous radiation from electron beams passing through a system of undulators. The code supports parallel architecture, and uses the HDF5 [2] technology to efficiently handle the multi-dimensional data. The latest developments and benchmarking are presented.
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title: QUINDI - A Code to Simulate Coherent Emission from Bending Systems
format: conference proceeding
conference: PAC 2007
year: 2007
3 authors: D. Schiller | S. Reiche | M. Ruelas
abstract: We present a newly developed code, QUINDI, to address the numerical challenge of calculating the radiation spectra from electron bunches in bending magnet systems. This code provides a better tool for designing diagnostic systems such as bunch length monitors in magnetic chicanes. The program calculates emission on a first principle basis, combining the dominant emission processes in a bending magnet system -- edge and synchrotron radiation. The core algorithm is based on the Lienard-Wiechert potential and utilizes parallel computer architecture to cover complete electron beam distributions with a high resolution spatial grid. The program models the coherence level of the emitted radiation from the electron bunch, focusing on long frequency components.
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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: 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: Status of the SPARC-X Project
format: conference proceeding
conference: PAC 2007
year: 2007
97 authors: C. Vaccarezza | D. Alesini | M. Bellaveglia | S. Bertolucci | R. Boni | M. Boscolo | M. Castellano | A. Clozza | L. Cultrera | G. Di Pirro | A. Drago | A. Esposito | M. Ferrario | L. Ficcadenti | D. Filippetto | V. Fusco | A. Gallo | G. Gatti | A. Ghigo | C. Ligi | Agostino Marinelli | M. Migliorati | A. Mostacci | E. Pace | L. Palumbo | L. Pellegrino | M. Preger | R. Ricci | C. Sanelli | M. Serio | F. Sgamma | B. Spataro | A. Stella | F. Tazzioli | M. Vescovi | C. Vicario | F. Ciocci | G. Dattoli | A. Dipace | A. Doria | F. Flora | G.P. Gallerano | L. Giannessi | E. Giovenale | G. Messina | P.L. Ottaviani | S. Pagnutti | G. Parisi | L. Picardi | M. Quattromini | A. Renieri | G. Ronci | C. Ronsivalle | M. Rosetti | E. Sabia | M. Sassi | A. Torre | A. Zucchini | M. Mattioli | D. Pelliccia | L. Catani | E. Chiadroni | A. Cianchi | E. Gabrielli | C. Schaerf | P. Musumeci | M. Petrarca | F. Alessandria | A. Bacci | R. Bonifacio | I. Boscolo | F. Broggi | C. De Martinis | F. Castelli | S. Cialdi | D. Giove | A. Flacco | C. Maroli | V. Petrillo | A.R. Rossi | L. Serafini | A. Perrone | M. Labat | O. Tcherbakoff | G. Lambert | D. Garzella | M. Bougeard | P. Breger | P. Monchicourt | H. Merdji | P. Salie?res | B. Carre? | M. E. Couprie | P. Emma | C. Pellegrini | S. Reiche | J.B. Rosenzweig
abstract: SPARC-X is a two branch project consisting in the SPARC test facility dedicated to the development and test of critical subsystems such as high brightness photoinjector and a modular expandable undulator for SASE-FEL experiments at 500 nm with seeding, and the SPARX facility aiming at generation of high brilliance coherent radiation in the 1.5-13 nm range, based on the achieved expertise. The projects are supported by MIUR (Research Department of Italian Government) and Regione Lazio. SPARC has completed the commissioning phase of the photoinjector in November 2006. The achieved experimental results are here summarized together with the status of the second phase commissioning plans. The SPARX project is based on the generation of ultra high peak brightness electron beams at the energy of 1 and 2 GeV generating radiation in the 1.5-13 nm range. The construction is at the moment planned in two steps starting with a 1 GeV Linac. The project layout including both RF-compression and magnetic chicane techniques has been studied.
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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.
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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.
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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: LASER BEAT-WAVE MICROBUNCHING OF RELATIVISTIC ELECTRON BEAM IN THE THZ RANGE
format: conference proceeding
conference: Linear Accelerator Conference 2006
year: 2006
6 authors: S. Ya. Tochitsky | S. Reiche | C. Sung | J.B. Rosenzweig | C. Pellegrini | C. Joshi
abstract: Laser-driven plasma accelerators have recently demonstrated a ~1GeV energy gain of self-trapped electrons in a several-centimeter-long plasma channel. Potential staging of such devices will require the external injection of an electron beam prebunched on the scale of 1-10 THz into a plasma accelerating structure or plasma LINAC. Seeded FEL/IFEL techniques can be used for modulation of the electron beam longitudinally on the radiation wavelength scale. However, a seed source in this spectral range is not available. At the UCLA Neptune Laboratory a Laser Beat-Wave (LBW) microbunching experiment has begun. The interaction of the electron beam and the LBW results in ponderomotive acceleration and energy modulation on the THz scale. This stage is followed by a ballistic drift of the electrons, where the gained energy modulation is transferred to the beam current modulation. Then the beam is sent into a 33-cm long undulator, where a coherent start-up of THz radiation takes place, and the THz pulse is used for a bunching analysis. The performance of LBW bunching is simulated and analyzed using a 3D FEL code for the parameters of an existing photoinjector and two-wavelength TW CO2 laser system.
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title: Development of a Waveguide FEL Seeded in the 1-3 THz Range for Microbunching Experiment at the Neptune Laboratory
format: conference proceeding
conference: AAC 2006 12th
year: 2006
8 authors: C. Sung | S. Ya. Tochitsky | S. Reiche | S. C. Gottschalk | W. D. Kimura | J.B. Rosenzweig | C. Pellegrini | C. Joshi
abstract: IFEL and FEL techniques can be used to modulate an electron beam on the scale of the radiation wavelength. However, the lack of a high power radiation source in the 100-300 ?m range hinders the progress on THz IFEL microbunching. In this paper, we discuss microbunching of an electron beam using a single-pass FEL seeded with a low power THz pulse generated by frequency mixing of CO2 laser lines in a GaAs nonlinear crystal. A narrowband THz seed source is pumped by a dual beam TEA CO2 laser and can be tuned in the 1-3 THz range. The THz radiation is guided through a hollow waveguide inside the planar FEL undulator driven by a photoinjector. By using a time-dependent FEL code GENESIS 1.3, we optimized the undulator parameters and analyzed the dynamics of the modulated electron beam. By using a ~ 8 MeV electron beam with a peak current of 40 A and a ~1kW THz seed with wavelength 200 ?m, the energy modulation up to 1.3% can be achieved in a ~1.8-m long undulator with a constant period of 2.7 cm. At present, the THz seed source is built and fully characterized. The results of transmission measurements for THz waveguides are also discussed.
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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: Status of the SPARX FEL Project
format: conference proceeding
conference: EPAC 2006
year: 2006
67 authors: C.Vaccarezza | D.Alesini | M.Bellaveglia | S.Bertolucci | M.E Biagini | R.Boni | M.Boscolo | M.Castellano | A.Clozza | L.Cultrera | G.Di Pirro | A.Drago | A.Esposito | M.Ferrario | D.Filippetto | V.Fusco | A.Gallo | A.Ghigo | S.Guiducci | M.Migliorati | L.Palumbo | L.Pellegrino | M.Preger | C.Sanelli | M.Serio | F.Sgamma | B.Spataro | A.Stella | F.Tazzioli | M.Vescovi | C.Vicario | F. Ciocci | G.Dattoli | A.Doria | F.Flora | G.Gallerano | L.Giannessi | E.Giovenale | G.Messina | P.L. Ottaviani | G.Parisi | L.Picardi | M.Quattromini | A.Renieri | C. Ronsivalle | S.Cialdi | C.Maroli | V.Petrillo | M. Rome | L.Serafini | L.Catani | E.Chiadroni | A. Cianchi | C.Schaerf | P.Musumeci | F.Alessandria | A.Bacci | F.Broggi | C.De Martinis | D.Giove | M.Mauri | L. Ficcadenti | M.Mattioli | A.Mostacci | P.Emma | S.Reiche | J.B. Rosenzweig
abstract: The SPARX project consists in an X-ray-FEL facility jointly supported by MIUR (Research Department of Italian Government), Regione Lazio, CNR, ENEA, INFN and Rome University Tor Vergata. It is the natural extension of the ongoing activities of the SPARC collaboration. The aim is the generation of electron beams characterized by ultra-high peak brightness at the energy of 1 and 2 GeV, for the first and the second phase respectively. The beam is expected to drive a single pass FEL experiment in the range of 13.5�6 nm and 6�1.5 nm, at 1 GeV and 2 GeV respectively, both in SASE and SEEDED FEL configurations. A hybrid scheme of RF and magnetic compression will be adopted, based on the expertise achieved at the SPARC high brightness photoinjector presently under commissioning at Frascati INFN-LNF Laboratories [1,2]. The use of superconducting and exotic undulator sections will be also exploited. In this paper we report the progress of the collaboration together with start to end simulation results based on a combined scheme of RF compression techniques.
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title: Status of the SPARC Photoinjector
format: conference proceeding
conference: Linear Accelerator Conference 2006
year: 2006
69 authors: D. Alesini | M. Bellaveglia | S. Bertolucci | R. Boni | M. Boscolo | M. Castellano | A. Clozza | L. Cultrera | G. Di Pirro | A. Drago | A. Esposito | M. Ferrario | L. Ficcadenti | D. Filippetto | V. Fusco | G. Gatti | A. Gallo | A. Ghigo | M. Incurvati | C. Ligi | F. Marcellini | M. Migliorati | A. Mostacci | L. Palumbo | L. Pellegrino | M. Preger | 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. DeMartinis | D. Giove | C. Maroli | M. Mauri | V. Petrillo | M. Rome | A. R. Rossi | L. Serafini | D. Levi | M. Mattioli | P. Musumeci | G. Medici | D. Pelliccia | M. Petrarca | L. Catani | E. Chiadroni | A. Cianchi | E. Gabrielli | S. Tazzari | A. Perrone | L. Giannessi | L. Picardi | M. Quattromini | C. Ronsivalle | J.B. Rosenzweig | G. Travish | S. Reiche
abstract: The SPARC Project is starting the commissioning of its photo-injector. RF gun, RF sources, RF network and control, power supplies, emittance meter, beam diagnostics and control to measure the RF gun beam have been installed. The photocathode drive laser has been characterized in terms of pulse shape and quality. We will report also about first tests made on RF gun and on the emittance meter device. Additional R&D on X-band and S-band structures for velocity bunching are in progress, as well as studies on new photocathode materials. We will also discuss studies on solenoid field defects, beam based alignments and exotic electron bunch production via blow-out of short laser pulses.
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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: The LCLS Single-shot Relative Bunch Length Monitor System
format: conference proceeding
conference: Erice 2005
year: 2006
4 authors: Sven Reiche | M. Dunning | G. Travish | J.B. Rosenzweig
abstract: The Particle Beam Physics Lab (PBPL) at UCLA is developing a single-shot relative bunch length monitor system for the Linac Coherent Light Source (LCLS) X-ray Free Electron Laser at SLAC. To ensure high-quality lasing, feedback systems are needed. The bunch length monitor system will be a crucial part of the linac longitudinal feedback system, which is necessary to keep the final peak beam current stable. The system will consist of two multi-channel single-shot grating polychromators, one after each bunch compressor, and will use the coherent synchrotron radiation (CSR) or coherent edge radiation (CER) from bunch compressor chicane dipole magnets. Details of the system will be presented, and the system will be compared to alternatives. Plans for testing and integration into the LCLS beamline will be presented as well.
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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: 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: 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: 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: 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.
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title: Feasibility Study of a Laser Beat-Wave Seeded THz FEL at the Neptune Laboratory
format: conference proceeding
conference: PAC 2005
year: 2005
6 authors: S. Reiche | C. Joshi | C. Pellegrini | J.B. Rosenzweig | S. Tochitsky | G. Shvets
abstract: Free-Electron Laser in the THz range can be used to generate high output power radiation or to modulate the electron beam longitudinally on the radiation wavelength scale. Microbunching on the scale of 1-5 THz is of partic- ular importance for potential phase-locking of a modulated electron beam to a laser-driven plasma accelerating struc- ture. However the lack of a seeding source for the FEL at this spectral range limits operation to a SASE FEL only, which denies a subpicosecond synchronization of the cur- rent modulation or radiation with an external laser source. One possibility to overcome this problem is to seed the FEL with two external laser beams, which difference (beat- wave) frequency is matched to the resonant FEL frequency in the THz range. In this presentation we study feasibility of an experiment on laser beat-wave injection in the THz FEL considered at the UCLA Neptune Laboratory, where both a high brightness photoinjector and a two-wavelength, TW-class CO2 laser system exist. By incorporating the energy modulation of the electron beam by the pondero- motive force of the beat-wave in a modified version of the time-dependent FEL code Genesis 1.3, the performance of a FEL at Neptune is simulated and analyzed.
keywords: pbpl  
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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.
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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
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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.
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title: Status Report on SPARC Project
format: conference proceeding
conference: FEL 2004 26th
year: 2004
96 authors: A. Renieri | M. Carpanese | 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 | G. Ronci | C. Ronsivalle | E. Sabia | M. Sassi | A. Zucchini | D. Alesini | M. Bellaveglia | S. Bertolucci | M.E. Biagini | C. Biscari | 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 | C. Milardi | L. Palumbo | L. Pellegrino | M. Preger | P. Raimondi | R. Ricci | C. Sanelli | M. Serio | F. Sgamma | B. Spataro | A. Stecchi | A. Stella | F. Tazzioli | C. Vaccarezza | M. Vescovi | C. Vicario | M. Zobov | F. Alessandria | A. Bacci | I. Boscolo | F. Broggi | S. Cialdi | C. De Martinis | D. Giove | C. Maroli | V. Petrillo | M. Romè | L. Serafini | D. Levi | M. Mattioli | G. Medici | P. Musumeci | L. Catani | E. Chiadroni | S. Tazzari | C.J. Bocchetta | M. Danailov | G. D'Auria | M. Ferianis | A. Cianchi | A. D'Angelo | R. Di Salvo | A. Fantini | D. Moricciani | C. Schaerf | S. Reiche | J.B. Rosenzweig | G. Travish | D.H. Dowell | P. Emma | C. Limborg | D. Palmer
abstract: We review the status of FEL source activity of the ongoing SPARC FEL experiment, developed within the framework of a collaboration among ENEA, CNR, INFN, INFM, Sincrotrone Trieste and University of Rome Tor Vergata. The project is aimed at realising a SASE-FEL source, operating in the visible (around 500 nm), with an extended range of tunability down to the VUV (100 nm) by the use of the mechanism of non-linear harmonic generation. The development of the relevant activities foresees the realisation of an advanced 150 MeV photo- injector source, aimed at producing a high brightness electron beams, needed to drive a SASE-FEL experiment, and a 14 m long undulator. We present the status of the design and construction of SPARC FEL device. In particular we discuss the choice of the project parameters, their optimisation and the sensitivity of the SPARC performance to any parameter variation. We will show, using start-to-end simulations, what is the impact of the e- beam and of the undulator parameters on the characteristics of the output laser field and in particular on the amount of the non-linearly generated power at higher harmonics.
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title: Spontaneous Radiation Background Calculation for LCLS
format: conference proceeding
conference: FEL 2004 26th
year: 2004
1 author: S. Reiche
abstract: The intensity of undulator radiation, not amplified by the FEL interaction, can be larger than the maximum FEL sig- nal in the case of an X-ray FEL. In the commissioning of a SASE FEL it is essential to extract an amplified signal early to diagnose eventual misalignment of undulator modules or errors in the undulator field strength. We developed a numerical code to calculate the radiation pattern at any position behind a multi-segmented undulator with arbitrary spacing and field profiles. The output can be run through numerical spatial and frequency filters to model the radiation beam transport and diagnostic. In this presentation we estimate the expected back- ground signal for the FEL diagnostic and at what point along the undulator the FEL signal can be separated from the background. We also discusses how much information on the undulator field and alignment can be obtained from the incoherent radiation signal itself.
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title: Generation of GW-level, sub-Angstrom Radiation in the LCLS using a Second-Harmonic Radiator
format: conference proceeding
conference: FEL 2004 26th
year: 2004
2 authors: Z. Huang | S. Reiche
abstract: Electron beams are strongly microbunched near the high-gain free-electron laser (FEL) saturation with a rich harmonic content in the beam current. While the coherent harmonic emission is possible in a planar undulator, the third- harmonic radiation typically dominates with about 1% of the fundamental power at saturation. In this paper, we discuss the second-harmonic radiation in the Linac Coherent Light Source. We show that by a suitable design of an second- stage undulator with its fundamental frequency tuned to the second harmonic of the first undulator, coherent second-harmonic radiation much more intense than the third-harmonic is emitted. Numerical simulations predict that GW-level, sub- Angstrom x-ray pulses can be generated in a relatively short second-harmonic radiator.
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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: 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.
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title: Current-Enhanced SASE Using an Optical Laser and its Application to the LCLS
format: conference proceeding
conference: FEL 2004 26th
year: 2004
6 authors: A.A. Zholents | W.M. Fawley | P. Emma | Z. Huang | G. Stupakov | S. Reiche
abstract: We propose a significant enhancement of the electron peak current entering a SASE undulator by inducing an en- ergy modulation in an upstream wiggler magnet via res- onant interaction with an optical laser, followed by mi- crobunching of the energy-modulated electrons at the ac- celerator exit. This current enhancement allows a reduc- tion of the FEL gain length. The x-ray output consists of a series of uniformly spaced spikes, each spike being tem- porally coherent. The duration of this series is controlled by the laser pulse and in principle can be narrowed down to just a single, -attosecond spike. Given potentially absolute temporal synchronization of the x-ray spikes to the energy-modulating laser pulse, this scheme naturally makes pump-probe experiments available to SASE FEL�s. We also study various detrimental effects related to the high electron peak current .
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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: 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: A Fast Method to Estimate the Gain of the Microbunch Instability in a Bunch Compressor
format: conference proceeding
conference: PAC 2003
year: 2003
2 authors: Sven Reiche | J.B. Rosenzweig
abstract: For the users of the high-brightness radiation sources of free-electron lasers it is necessary to reduce the FEL pulse length to 10 fs and below for time-resolving pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of undulator wakefields and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented.
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title: Theoretical evaluation of the LCLS X-Ray Free-Electron Laser performance
format: conference proceeding
conference: FEL 2003 25th
year: 2003
4 authors: Sven Reiche | C. Pellegrini | P. Emma | Nuhn, H. D.
abstract: In this paper we evaluate the performance of the LCLS FEL, including all known physical effects from the electron source to the undulator exit which determine the X-ray pulse characteristics. The wavelength range considered is from the 15 to 1.5 Angstrom, with an extension to 0.5 Angstrom using the third harmonic. The results of this work have been useful to identify areas in the LCLS design where improvements could be made, thus optimizing the system performance.
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title: Start-to-End Simulations for the LCLS X-Ray Free-Electron Laser
format: conference proceeding
conference: FEL 2003 25th
year: 2003
7 authors: Sven Reiche | C. Pellegrini | P. Emma | Nuhn, H. D. | Limborg, C. G. | Borland, M. | W. Fawley
abstract: The LCLS Free-Electron Lasers operates in the wavelength range of 1.5-15 Angstrom, using an electron beam with an energy between 4.5 and 14.5 GeV. The generation of the electron beam, the preservation of its brightness during acceleration and compression, and the amplififcation of the spontaneous radiation within the FEL can only be described by a consistent set of simulation codes. We preset the change in the FEL performance with respect to the LCLS design case, when various effects are included, altering the electron beam distribution and motion (e.g. wake fields, CSR, magnet misalignment or field errors of the undulator field). To distinguish the individual contribution of each effect, multiple start-end simulations are performed, including step by step additional effects and, thus, approaching a more and more realistic model of the LCLS FEL.
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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: Pulse Length Control in an X-Ray FEL by Using Wakefields
format: conference proceeding
conference: PAC 2003
year: 2003
3 authors: Sven Reiche | P. Emma | C. Pellegrini
abstract: For the users of the high-brightness radiation sources of free-electron lasers it is necessary to reduce the FEL pulse length to 10 fs and below for time-resolving pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of undulator wakefields and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented.
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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: 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.
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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.
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title: Free-Electron Simulations at Short Wavelengths
format: preprint
year: May 01, 2002
1 author: Sven Reiche
abstract: Outline: FEL Simulations Overview Codes Shot-Noise Models Short Wavelength Effects Spontaneous Radiation Wake Fields Undulator Description Start-End Simulations
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title: Gain Computation
format: preprint
year: April 24, 2002
1 author: Sven Reiche
abstract:
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title: Comparison of the FEL and CSR Instabilities
format: preprint
year: April 19, 2002
1 author: Sven Reiche
abstract: FEL and CSR instabilities have same principle of interaction between electron beam and synchrotron radiation, but the signature is different for the different longitudinal scales. Beside the FEL these instabilities are regarded as degrading affects on the beam properties, imposing limitation on the operation range of the accelerator.
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title: A fast method to estimate the gain of the microbunch instability in a bunch compressor
format: conference proceeding
conference: FEL 2002 24th
year: 2003
2 authors: Sven Reiche | J.B. Rosenzweig
abstract: To reach high peak currents driving Free-Electron Lasers an initial chirped electron bunch is compressed in a bunch compressor. The interaction of the electron beam with its radiation field can yield a collective instability, which amplifies any initial modulation in the current profile. We present a model, which allows to derive an explicit analytical expression for the gain of the microbunch instability. The results are compared to those of the more complex analytical models.
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title: Results of the VISA SASE FEL Experiment at 840 nm
format: conference proceeding
conference: FEL 2002 24th
year: 2003
26 authors: A. Murokh | R. Agustsson | M. BABZIEN | I. Ben-Zvi | L. Bertolini | K. van Bibber | R. Carr | M. Cornacchia | P. Frigola | J. Hill | E. Johnson | L. Klaisner | G.P. Le Sage | M. Libkind | R. Malone | H-D. Nuhn | C. Pellegrini | Sven Reiche | G. Rakowsky | J.B. Rosenzweig | Ruland, R. | Skaritka, J. | A. Toor | A. Tremaine | X. Wang | V. Yakimenko
abstract: VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission (SASE) free-electron laser (FEL), which achieved saturation at 840 nm within a single-pass 4-m undulator. A gain length shorter than 18 cm has been obtained, yielding the gain of 2x10(8) at saturation. The FEL performance, including the spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. The results are compared to 3-D SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL system. Detailed agreement between simulations and experimental results is obtained over the wide range of the electron beam parameters.
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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: Pulse length control in an X-ray FEL by using wakefields
format: conference proceeding
conference: FEL 2002 24th
year: 2003
3 authors: Sven Reiche | P. Emma | C. Pellegrini
abstract: For the users of the high-brightness radiation sources of free-electron lasers it is desirable to reduce the FEL pulse length to 10 fs and below for time-resolving pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of longitudinal wakefields in the undulator and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented.
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title: Measurements of nonlinear harmonic radiation and harmonic microbunching in a visible SASE FEL
format: conference proceeding
conference: FEL 2002 24th
year: 2003
13 authors: A. Tremaine | X. J. Wang | M. Babzien | I. Ben-Zvi | M. Cornacchia | R. Malone | A. Murokh | H. D. Nuhn | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | Skaritka, J. | V. Yakimenko
abstract: The experimental characterization of nonlinear harmonic generation (NHG) and electron beam microbunching at saturation from a visible SASE FEL are presented in this report. The gain lengths, spectra and energies of NHG were experimentally measured up to the third harmonic, and agree with theoretical predictions. Electron beam microbunching in both the fundamental and the second harmonic as the function of the SASE output were experimentally observed over the full range of SASE gain. The bunching factors for both the fundamental (b(1)) and second harmonic (b(2)) were experimentally characterized at saturation. The microbunching data provides another test of SASE saturation as well as correlating the NHG and electron beam microbunching modes to the fundamental SASE.
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title: Fundamental and Harmonic Microbunching Measurements in a High-Gain, Self-Amplified, Spontaneous Emission Free-Electron Laser
format: preprint
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 | Skaritka, J. | V. Yakimenko
abstract: The self-amplified, spontaneous emission free-electron laser (SASE-FEL) gain process is a collective instability which induces microbunching in the electron beam. Micro-bunching approaching unity at the fundamental FEL wavelength (845 nm), and its second harmonic, have been measured at the VISA FEL, at or near saturation. These measurements, which use the beam's coherent transition radiation (CTR) spectrum, are sompared to the predictions of FEL simulations. Comparison of shot-by-shot SASE and CTR signals firmly establishes the role of SASE in the development of microbunching harmonics.
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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.
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title: Properties of an Ultra-Short Gain Length, Saturated, Self-Amplified Spontaneous Emission FEL
format: preprint
year: 2002
26 authors: A. Murokh | R. Agustsson | Pedro Frigola | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | A. Tremaine | M. Babzien | I. Ben-Zvi | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X. Wang | V. Yakimenko | L. Bertolini | J. M. Hill | G.P. Le Sage | M. Libkind | A. Toor | K. A. Van Bibber | R. Carr | M. Cornacchia | L. Klaisner | H. D. Nuhn | Ruland, R.
abstract: The VISA experiment, conducted at the BNL Accelerator Test Facility (ATF), has studied the properties of SASE FEL process in a saturating system. The experiment utilized a high brightness electron beam and a strong focusing undulator. Saturated gain greater than 108, with a power gain length below 18 cm, was obtained at 840 nm. Measurements of FEL gain, spectral and angular properties of SASE radiation are reported, and the results are compared to theory and to start-to-end simulations of the system. FEL performance was found critically dependent on the compression of the electron beam.
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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.
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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).
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title: Two-Stage Chirped-Beam SASE-FEL for High Power Femtosecond X-Ray Pulse Generation
format: preprint
year: December 10, 2001
5 authors: C. Schroeder | J. Arthur | P. Emma | Sven Reiche | C. Pellegrini
abstract:
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title: Status of the 3D Time-Dependent FEL Simulation Code GENESIS 1.3
format: conference proceeding
conference: FEL 2001 23rd
year: 2002
2 authors: Sven Reiche | B. Faatz
abstract: Since its release in 1999 the 3D time-dependent code GENESIS 1.3 has become a helpful tool for the design-studies and analysis of a single-pass Free-Eelectron Lasers experiments. With the latest version new features have been added such as support for wake-fields and incoherent spontaneous radiation. In addition the more modular structure of the open-source code and the improved support of external imput files allow a better understanding of the code, supporting users who want to add new features to the code.
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title: Chirped-beam two-stage SASE-FEL for high power femtosecond X-ray pulse generation
format: conference proceeding
conference: FEL 2001 23rd
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 using a single-pass free-electron laser (FEL) is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped X-ray pulse through self-amplified spontaneous emission (SASE). After the undulator, we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse; therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE?FEL, and consider the performance of the chirped-beam two-stage option for the Linac Coherent Light Source.
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title: Characterization of an 800 nm SASE FEL at saturation
format: conference proceeding
conference: FEL 2001 23rd
year: 2002
24 authors: A. Tremaine | Pedro Frigola | A. Murokh | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | M. Babzien | I. Ben-Zvi | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X. J. Wang | K. A. Van Bibber | L. Bertolini | J. M. Hill | G.P. Le Sage | M. Libkind | A. Toor | R. Carr | M. Cornacchia | L. Klaisner | H. D. Nuhn | Ruland, R.
abstract: Visible to Infrared SASE Amplifier is a free electron laser (FEL) designed to saturate at a radiation wavelength of 800 nm within a 4 m long, strong focusing undulator. A large gain is achieved by driving the FEL with 72 MeV, high brightness beam of BNL's accelerator test facility. We present measurements that demonstrate saturation in addition to the frequency spectrum of the FEL radiation. Energy, gain length and spectral characteristics are compared and shown to agree with simulation and theoretical predictions. (16 References).
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title: The BESSY FEL Project
format: conference proceeding
conference: FEL 2001 23rd
year: 2002
20 authors: M. Abo-Bakr | W. Anders | J. Bahrdt | R. Bakker | W. Eberhardt | B. Faatz | R. Follath | A. Gaupp | M. v. Hartrott | E. Jaeschke | D. Kraemer | P. Kuske | M. Martin | R. Mueller | H. Prange | Sven Reiche | W. Sandner | F. Senf | I. Will | G. Wustefeld
abstract: Berliner Elektronenspeicherring-Gesellschaft fur Synchrotronstrahlung (BESSY) plans to construct a linac-based single-pass FEL as an addition to its existing third generation storage-ring-based light-source. The project aims to obtain an FEL-based user-facility that covers the VUV and soft X-ray spectral range (20 eV less than or equal to homega less than or equal to 1 keV). At present, the design stage is funded as a collaboration between BESSY, DESY, the Hahn-Meitner-Institute in Berlin, and the Max-Born-Institute in Berlin. This stage focuses on optimization of the FEL as a user light-source, both with respect to its capabilities and in its performance. Important issues are: stability, seeding options of the SASE FEL, wavelength-tunability, synchronization with external laser sources and, on a longer time-scale, the generation of ultra-short (< 20 fs RMS) optical pulses.
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title: Start-to-end simulation for the LCLS X-ray FEL
format: conference proceeding
conference: FEL 2001 23rd
year: 2002
5 authors: S. Reiche | C. Pellegrini | J.B. Rosenzweig | P. Emma | P. Krejcik
abstract: X-ray FELs, such as the LCLS and TESLA FEL, require electron beams with large peak current and very small emittance. The X-ray peak power, temporal and spectral properties, depend significantly on details of the electron beam phase space distribution. The electron beam distribution is determined by many effects, as the emission process at the gun photo-cathode, bunch compression, acceleration and wakefields within the undulator. Although analytical results can give an estimate of the expected performance, the complexity of the electron beam generation, acceleration and compression can only be evaluated using a numerical simulation of all these processes, a start-to-end simulation. In this presentation we discuss the LCLS X-Ray FEL performance estimated by a start-to-end simulation, and we compare the results with those obtained using a simpler model. (20 References).
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title: Measuring FEL radiation properties at VISA-FEL
format: conference proceeding
conference: PAC 2001
year: 2001
25 authors: A. Murokh | R. Agustsson | Pedro Frigola | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | A. Tremaine | M. Babzien | I. Ben-Zvi | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X. J. Wang | K. A. Van Bibber | L. Bertolini | J. M. Hill | G.P. Le Sage | M. Libkind | A. Toor | R. Carr | M. Cornacchia | L. Klaisner | H. D. Nuhn | Ruland, R.
abstract: The VISA (Visible to Infrared SASE Amplifier) SASE free electron laser has been successfully operated at the Accelerator Test Facility (ATF) at BNL. High gain and saturation were observed at 840 nm. We describe here the diagnostic system, experimental procedures and data reduction algorithms, as the FEL performance was measured along the length of the undulator. We also discuss selected spectral radiation measurements. (10 References).
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title: Saturation measurements of a visible SASE FEL
format: conference proceeding
conference: PAC 2001
year: 2001
14 authors: A. Tremaine | P. Frigola | A. Murokh | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | M. Babzien | I. Ben-Zvi | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X. J. Wang | V. Yakimenko
abstract: VISA (visible to infrared SASE amplifier) is an FEL designed to obtain high gain at a radiation wavelength of 800 nm. Large gain is achieved by driving the FEL with the 71 MeV, high brightness beam of the Accelerator Test Facility (ATF) and using a novel, strong focusing, 4 m long undulator with a gap of 6 mm and a period of 1.8 cm. We report measurements of exponential gain, saturation, and spectra of the FEL radiation intensity. (11 References).
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title: Proposal for a IR Waveguide SASE FEL at the PEGASUS Injector
format: conference proceeding
conference: PAC 2001
year: 2001
3 authors: Sven Reiche | J.B. Rosenzweig | S. Telfer
abstract: Free Electron Lasers up to the visible regime are dominated by diffraction effects, resulting in a radiation size much larger than the electron beam. Thus the effective field amplitude at the location of the electron beam, driving the FEL process, is reduced. By using a waveguide, the radiation field is confined within a smaller aperture and an enhancement of the FEL performance can be expected. The PEGASUS injector at UCLA will be capable to provide the brilliance needed for an IR SASE FEL. The experiment PERSEUS (Power Enhanced Radiation Source Experiment Using Structures) is proposed to study the physics of a waveguide SASE FEL in a quasi 1D environment, where diffraction effects are strongly reduced as it is the case only for future FELs operating in the VUV and X-ray regime. The expected FEL performance is given by this presentation.
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title: Start-to-end simulation for the LCLS X-ray FEL
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: Sven Reiche | C. Pellegrini | J.B. Rosenzweig | P. Emma | P. Krejcik
abstract: X-ray FELs, such as the LCLS and TESLA FEL, require electron beams with large peak current and very small emittance. The X-ray peak power, temporal and spectral properties, depend significantly on details of the electron beam phase space distribution. The electron beam distribution is determined by many effects, as the emission process at the gun photo-cathode, bunch compression, acceleration and wakefields within the undulator. Although analytical results can give an estimate of the expected performance, the complexity of the electron beam generation, acceleration and compression can only be evaluated using a numerical simulation of all these processes, a start-to-end simulation. In this presentation we discuss the LCLS X-Ray FEL performance estimated by a start-to-end simulation, and we compare the results with those obtained using a simpler model. (19 References).
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title: Transition radiation for uneven, limited surfaces
format: conference proceeding
conference: PAC 2001
year: 2001
2 authors: Sven Reiche | J.B. Rosenzweig
abstract: In the most common approach to modeling transition radiation, the annihilation of the incident particle with its image particle at the metallic boundary is calculated. This is valid only for ideal planar boundaries, and is not applicable if the surface is modulated, rough or limited in the transverse dimension. In this paper, we show results obtained by replacing the image current with the induced surface charge and surface distributions. Special problems such as a modulated surface are analytically solved and compared to a numerical simulation. Implications for experimental use of transition radiation-based beam monitors are discussed. (9 References).
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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: Chirped-beam two-stage SASE-FEL for high power femtosecond x-ray pulse generation
format: conference proceeding
conference: Conference on Optics for Fourth-Generation X-Ray Sources
year: 2001
5 authors: C. B. Schroeder | C. Pellegrini | Sven Reiche | J. Arthur | P. Emma
abstract: We present a method for generating femtosecond duration x-ray pulses using a single-pass free-electron laser (FEL). This method uses an energy-chirped electron beam to produce a frequency-chirped x-ray pulse through self-amplified spontaneous emission (SASE). After the undulator we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse, and therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE-FEL, and consider the performance of the chirped-beam two-stage option for the Linac Coherent Light Source (LCLS).
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title: Chirped-beam two-stage SASE-FEL for high power femtosecond X-ray pulse generation
format: conference proceeding
conference: PAC 2001
year: 2001
5 authors: C.B. Schroeder | C. Pellegrini | S. Reiche | J. Arthur | P. Emma
abstract: We present a method for generating femtosecond duration X-ray pulses using a single-pass free-electron laser (FEL). This method uses an energy-chirped electron beam to produce a frequency-chirped X-ray pulse through self-amplified spontaneous emission (SASE). After the undulator we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse, and therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE-FEL, and consider the performance of the chirped-beam two-stage option for the for the Linac Coherent Light Source (LCLS).
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title: Initial gain measurements of an 800 nm SASE FEL, VISA
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
26 authors: P. Frigola | A. Murokh | P. Musumeci | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | A. Tremaine | M. Babzien | I. Ben-Zvi | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X. J. Wang | K. A. Van Bibber | L. Bertolini | J. M. Hill | G.P. Le Sage | M. Libkind | A. Toor | R. Carr | M. Cornacchia | L. Klaisner | H. D. Nuhn | Ruland, R. | D. C. Nguyen
abstract: The visible to infrared SASE amplifier (VISA) FEL is designed to obtain high gain at a radiation wavelength of 800 nm. The FEL uses the high brightness electron beam of the accelerator test facility (ATF), with energy of 72 MeV. VISA uses a novel, 4 m long, strong focusing undulator with a gap of 6 mm and a period of 1.8 cm. To obtain large gain the beam and undulator axis have to be aligned to better than 5 mu m. Results from initial measurements on the alignment, gain, and spectrum will be presented and compared to theoretical calculations and simulations. (10 References).
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title: Proposal for a IR waveguide SASE FEL at the PEGASUS injector
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
3 authors: Sven Reiche | J.B. Rosenzweig | S. Telfer
abstract: Free Electron Lasers up to the visible regime are dominated by diffraction effects, resulting in a radiation size much larger than the electron beam. Thus the effective field amplitude at the location of the electron beam, driving the FEL process, is reduced. By using a waveguide, the radiation field is confined within a smaller aperture and an enhancement of the FEL performance can be expected. The PEGASUS injector at UCLA will be capable to provide the brilliance needed for an IR SASE FEL. The experiment Power Enhanced Radiation Source Experiment Using Structures (PERSEUS) is proposed to study the physics of a waveguide SASE FEL in a quasi I D environment, where diffraction effects are strongly reduced as it is the case only for future FELs operating in the VUV and X-ray regime. The expected FEL performance is given by this presentation.
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title: Optimization of an x-ray SASE-FEL
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
7 authors: C. Pellegrini | Sven Reiche | J.B. Rosenzweig | C. Schroeder | A. A. Varfolomeev | Tolmachev, S. | H. D. Nuhn
abstract: The most important characteristics of an X-ray SASE-FEL are determined by the electron beam energy, transverse and longitudinal emittance, and by choice of the undulator period, field, and gap. Among them are the gain and saturation length, the amount and spectral characteristics of the spontaneous radiation, the wake fields due to the vacuum pipe. The spontaneous radiation intensity is very large in all X-ray SASE-FELs now being designed, and it contributes to the final electron beam energy spread, thus affecting the gain. It also produces a large background for the beam and radiation diagnostics instrumentation. The wake fields due to the resistivity and roughness of the beam pipe through the undulator, also affects the beam 6-dimensional phase space volume, and thus the gain and the line width. In this paper, we discuss ways to optimize the FEL when considering all these effects. In particular we consider and discuss the use of a hybrid iron-permanent magnet helical undulator to minimize some of these effects, and thus optimize the FEL design.
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title: The PEGASUS free electron laser laboratory
format: conference proceeding
conference: FEL 2000 22nd
year: 2001
4 authors: S. Telfer | Sven Reiche | J.B. Rosenzweig | P. Frigola
abstract: The PEGASUS (Photoelectron Generated Amplified Spontaneous Radiation Source) free electron laser laboratory is currently being commissioned at UCLA.
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title: Optimization of an X-ray SASE FEL
format: conference proceeding
conference: ICFA Beam Dynamics Workshop on Physics of, and Science with, the X-Ray Free-Electron Laser 19th
year: 2001
7 authors: C. Pellegrini | Sven Reiche | J.B. Rosenzweig | C. Schroeder | A. A. Varfolomeev | Tolmachev, S. | H-D. Nuhn
abstract: The most important characteristics of an X-ray SASE-FEL are determined by the electron beam energy, transverse and longitudinal emittance, and by choice of the undulator period, field, and gap. Among them are the gain and saturation length, the amount and spectral characteristics of the spontaneous radiation, the wake fields due to the vacuum pipe. The spontaneous radiation intensity is very large in all X-ray SASE-FELs now being designed, and it contributes to the final electron beam energy spread, thus affecting the gain. It also produces a large background for the beam and radiation diagnostics instrumentation. The wake fields due to the resistivity and roughness of the beam pipe through the undulator, also affects the beam 6-dimensional phase space volume, and thus the gain and the line width. In this paper, we discuss ways to optimize the FEL when considering all these effects. In particular we consider and discuss the use of a hybrid iron-permanent magnet helical undulator to minimize some of these effects, and thus optimize the FEL design.
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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.
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title: Simulation of time-dependent energy modulation by wake fields and its impact on gain in the VUV free electron laser of the TESLA Test Facility
format: conference proceeding
conference: FEL 1999 21st
year: 2000
2 authors: Sven Reiche | H. Schlarb
abstract: For shorter bunches and narrower undulator gaps the interaction between the electrons in the bunch and the wake fields becomes so large that the FEL amplification is affected. For a typical vacuum chamber of an X-ray or VUV Free Electron Laser three major sources of wake fields exist: a resistance of the beam pipe, a change in the geometric aperture and the surface roughness of the beam pipe. The generated wake fields, which move along with the electrons, change the electron energy and momentum, depending on the electron longitudinal and transverse position. In particular, the accumulated energy modulation shifts the electrons away from the resonance condition. Based on an analytic model the energy loss by the wake fields has been incorporated into the time-dependent FEL simulation code GENESIS 1.3. For the parameters of the TESLA Test Facility the influence of the bunch length, beam pipe diameter and surface roughness has been studied. The results are presented in this paper.
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title: Compensation of FEL gain reduction by emittance effects in a strong focusing lattice
format: conference proceeding
conference: FEL 1999 21st
year: 2000
1 author: Sven Reiche
abstract: As the constraint of a small transverse emittance becomes more severe, the higher the electron beam energy in an FEL. To compensate for the transverse and thus the longitudinal velocity spread. a compensation scheme has been proposed previously by Derbenev and Sessler et al., for Free Electron Lasers by introducing a correlation between the energy and the average betatron amplitude of each electron. This compensation scheme is based on a constant absolute value of the transverse velocity, a feature of the natural focusing of undulators. and does not include strong focusing of a superimposed quadrupole lattice. This paper focuses on the electron motion in a strong focusing lattice with a variation in the axial velocity. The resulting reduction of the compensation efficiency is analyzed using simulations. It is seen that the compensation scheme is not much affected if the lattice cell length is shorter than the gain length. For the results presented in this paper, the parameters of the proposed TESLA X-ray FEL have been used.
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title: A method for measuring the FEL radiation power along an undulator
format: conference proceeding
conference: FEL 1999 21st
year: 2000
1 author: Sven Reiche
abstract: A highly desirable measurement in Free Electron Laser (FEL) experiments is the dependency of the radiation power along the undulator. Most designs of undulators prohibit detection of the radiation power within the undulator or extracting the electron beam at arbitrary positions. Transport of both, the radiation field and the electron beam, through the entire undulator, and thus an ongoing FEL interaction, is unavoidable. If there are many correction magnets distributed along the beam pipe, one can think of exciting a large orbit distortion downstream from any of these correctors. For a gain length comparable to or larger than the beta function this excitation of a coherent betatron oscillation might degrade the FEL amplification to a level, for which the radiation power does not further grow over the remaining length of the undulator. This paper presents the efficiency of this method for the parameters of the VUV FEL at the TESLA Test Facility.
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title: Multi-dimensional free-electron laser simulation codes: a comparison study
format: conference proceeding
conference: FEL 1999 21st
year: 2000
8 authors: S. G. Biedron | Y. C. Chae | R. J. Dejus | B. Faatz | H. P. Freund | S. V. Milton | H. D. Nuhn | Sven Reiche
abstract: A self-amplified spontaneous emission (SASE) free-electron laser(FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.
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title: Numerical Studies for a Single Pass High Gain Free-Electron Laser
format: thesis
year: 1999
1 author: Sven Reiche
abstract: The impo rtance of single pass high gain Free-Electron Lasers (FEL) is due to its the unique char acteristic of the short, high intense radiati on pulse at a well defined, tunable frequency. Extending the radiation wavelength to the ultra violet or X-ray region is an on-going research project and will open new branches of experiments based on this radiation. Several projects are proposed or currently unde rc onstruction such as the integrated X-ray FEL at the TESLA linear collider and the VUV FEL at the TESLA Test Facility. For all of these projects a detailed study is of importance, including all effects which might influence the FEL performan ce. In particular, for an FEL operating at X-ray wavelengths, the amplification process is more sensitive to any kind of disturbance. Some of these perturbations influence the FEL per formance in a complex way. Because existing codes are not capable to cover these proble ms the simulation cod eGEN ESIS 1.3 h as b een developed. The new features of GENESIS 1.3 incl udes the discretization of the radiation field on a Cartesian grid and the input of arbitrary profiles of the undulator field and the electron beam in longitudinal direction. The code is capable of covering aspects such as beam halos, wake fields a nd non-periodic focusing structures to name a few. Using GENESIS 1.3 special aspects of the TTF-FEL and TESLA FEL have been studied. The simulation cove rs the transverse motion of the electron beam, the impact of wake fields as well as the increase of the energy spread due to the qua ntum fluctuation of the incoherently emitted radiation.
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title: The APS SASE FEL: Modeling and code comparison
format: conference proceeding
conference: PAC 1999
year: 1999
8 authors: S. G. Biedron | Y. C. Chae | R. J. Dejus | B. Faatz | H. P. Freund | S. Milton | H. D. Nuhn | Sven Reiche
abstract: A self-amplified spontaneous emission (SASE) free electron laser (FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.
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title: Upgrade of the simulation code TDA3D
format: conference proceeding
conference: FEL 1998 20th
year: 1999
2 authors: Sven Reiche | B. Faatz
abstract: The well-known Free Electron Laser (FEL) amplifier simulation code TDA3D has been upgraded to include most of the important features needed for present and future design studies of VUV and X-ray single-pass FELs. A number of bugs have been removed and I/O has been changed and extended to make it more flexible. To features such as wiggler errors, quadrupole misalignment has been added and corrector coils to adjust the beam trajectory. In addition, multi-section undulators can now be simulated with arbitrary (integrated or separated) focusing structures.
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title: GENESIS 1.3: a fully 3D time-dependent FEL simulation code
format: conference proceeding
conference: FEL 1998 20th
year: 1999
1 author: Sven Reiche
abstract: Numerical simulation codes are basic tools for designing Free Electron Lasers (FEL). They are used to study the impact of different parameters, e.g. wiggler errors and external focusing, which allow FEL users to optimize the performance. For faster execution some simulation codes assume radial symmetry or decompose the radiation field into a few azimuthal modes, although then this treatment does not include the full description of the FEL. This contribution describes the new FEL code GENESIS 1.3 which uses a fully three-dimensional representation of the FEL equations in the paraxial approximation for time-dependent and steady-state simulations of single-pass FEL. In particular this approach is suitable for cases where the radial symmetry is broken by the electron beam distribution as well as by wiggler errors, betatron motion and off axis injection of the electron beam. The results, presented here, are based on the parameters of the TESLA Test Facility FEL at DESY.
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title: Influence of electron beam halos on the FEL performance
format: conference proceeding
conference: FEL 1998 20th
year: 1999
2 authors: B. Faatz | Sven Reiche
abstract: For single-pass free-electron lasers (FEL), such as amplifiers and SASE devices, saturation of the radiation power has to be reached within the length of the undulator. Therefore, detailed knowledge of electron beam parameters is crucial. So far, simulations have been performed with a given rms emittance and energy spread. At short radiation wavelengths, hunch compressors are used to compress the electron beam to achieve the desired high peak currents. In addition, external focusing along the entire undulator is used to maintain a constant small radius. The rotation of phase space due to compression might lead to a significant part of the bunch in tails that could increase the gain length. Furthermore, it is in general not possible to match both the beam core and the tail to the focusing structure. In this contribution, the influence of these tails, both transverse and in energy, on the FEL performance will be investigated. Simulations will be performed for beam parameters that have been assumed for the TESLA Test Facility FEL at DESY.
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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.
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title: Experimental measurement of high-gradient standing wave accelerator transport matrix
format: conference proceeding
conference: PAC 1997
year: 1998
3 authors: Sven Reiche | J.B. Rosenzweig | L. Serafini
abstract: This paper presents an experimental study of the transverse beam dynamics of an electron beam in a high-gradient, standing wave linear accelerator. A 3.6 MeV beam from the UCLA RF Photoinjector (SATURNUS) is injected at various phases and rf field amplitudes into the plane wave transformer (PWT) linac (peak acceleration 40 MeV/m), and its transverse dynamics measured by a corrector magnet sweeping method. This method allows us to reconstruct the transverse matrix elements, which are compared to analytical predictions (J.B. Rosenzweig and L. Serafini, Physical Review E 49, 1599 (1994)). The determinant of the experimentally derived matrix is found to be the ratio of the initial to final momentum, verifying the theory, and providing direct evidence of adiabatic damping of transverse trace space. (9 References).
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title: Measurements of high gain and noise fluctuations in a SASE free electron laser
format: conference proceeding
conference: FEL 1997 19th
year: 1998
12 authors: M. Hogan | S. Anderson | K. Bishofberger | P. Frigola | A. Murokh | N. Osmanov | C. Pellegrini | S. Reiche | J.B. Rosenzweig | G. Travish | A. Tremaine | A.A. Varfolomeev
abstract: We report measurements of large gain for a single pass free-electron laser operating in self-amplified spontaneous emission (SASE) at 16 mu m starting from noise. We also report the first observation and analysis of intensity fluctuations of the SASE radiation intensity in the high-gain regime. The results are compared with theoretical predictions and simulations. (11 References).
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title: Numerical study of X-ray FELs including quantum fluctuation
format: conference proceeding
conference: Workshop on Single Pass, High Gain FELs Starting from Noise Aiming at Coherent X-Rays
year: 1997
4 authors: Sven Reiche | E. L. Saldin | E. A. Schneidmiller | M. V. Yurkov
abstract: One of the fundamental limitations towards achieving very short wavelength in a self amplified spontaneous emission free electron laser (SASE FEL) is connected with the energy diffusion in the electron beam due to quantum fluctuations of undulator radiation. Parameters of the LCLS and TESLA X-ray FEL projects are very close to this limit and there exists necessity in upgrading FEL simulation codes for optimization of SASE FEL for operation at a shortest possible wavelength. In this report we describe a one-dimensional FEL simulation code taking into account the effects of incoherent undulator radiation. Using similarity techniques we have calculated universal functions describing degradation of the FEL process due to quantum fluctuations of undulator radiation.
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title: Measurements of high gain and noise fluctuations in a SASE free electron laser
format: conference proceeding
conference: Workshop on Single Pass, High Gain FELs Starting from Noise Aiming at Coherent X-Rays
year: 1997
12 authors: M. Hogan | S. Anderson | K. Bishofberger | Pedro Frigola | A. Murokh | N. Osmanov | C. Pellegrini | Sven Reiche | J.B. Rosenzweig | G. Travish | A. Tremaine | A. A. Varfolomeev
abstract: We report measurements of large gain for a single pass Free Electron Laser operating in Self Amplified Spontaneous Emission (SASE) at 16 mu m starting from noise. We also report the first observation and analysis of intensity fluctuations of the SASE radiation intensity in the high gain regime. The results are compared with theoretical predictions and simulations. (11 References).
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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.
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title: TDA3D: Updates and improvements to the widely used three-dimensional free electron laser simulation
format: conference proceeding
conference: FEL 1996 18th
year: 1997
7 authors: B. Faatz | W. Fawley | P. Pierini | Sven Reiche | G. Travish | D. Whittum | J. Wurtele
abstract: TDA3D is a widely distributed and often used Free Electron Laser (FEL) simulation code. While a number of versions of TDA exist, this paper describes the official version which is well tested and supported. We describe the capabilities of the code emphasizing recent improvements and revisions. TDA3D is a steady-state (time-independent) amplifier code. The code self-consistently solves, after averaging over a wiggler period, the paraxial wave equation for the radiation field and the Lorentz equations of motion for the electrons. The paraxial wave equation includes diffraction and optical guiding. The calculation of the electron beam motion takes into account longitudinal bunching and transverse betatron oscillations, so that emittance, energy spread, and external focusing can be properly modeled. Recent additions to the simulation include the ability to model natural wiggler focusing in one or both planes, alternating gradient quadrupoles or sextupoles, and ion channels. The initial loading of the electron distribution can be controlled to allow for matching into focusing channels, improved quiet starts (non-correlated phase-space distributions), and arbitrary energy spread.
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