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FEL 1999 21st

Name: FEL 1999 21st

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Date: 1999-01-01

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Created at: Fri Jul 27 23:53:36 -0700 2007

Updated at: Fri Jul 27 23:53:36 -0700 2007

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8 papers from the conference:

title: A diagnostic system to measure SASE-FEL radiation properties along the 4-meter VISA undulator
format: conference proceeding
conference: FEL 1999 21st
year: 2000
4 authors: A. Murokh | E. Johnson | J.B. Rosenzweig | A. Tremaine
abstract: During the last several years there has been a great experimental effort in the developing high gain SASE free electron lasers. Single pass FEL gain of 10 5 was achieved in the far infrared [ 1 ]. The research is directed towards smaller wavelengths and yet higher gain, with the ultimate goal of constructing the x-ray FEL [ 2 ]. A number of experiments are under the development to demonstrate SASE at visible and UV range. However, many important properties of the process of self-amplified spontaneous emission are still to be verified experimentally. As a part of the VISA experimental program (visible-to-infrared SASE amplifier [ 3 , 4 ]), we have constructed a diagnostics system, which will allow a detailed characterisation of the FEL process along the 4 meters of VISA undulator.
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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: High power femtosecond pulses from an X-ray SASE-FEL
format: conference proceeding
conference: FEL 1999 21st
year: 2000
1 author: C. Pellegrini
abstract: We discuss how to use the large-gain bandwidth of an X-ray SASE-FEL to produce femtosecond long pulses by chirping and compressing the output FEL radiation. We consider the power level, spectral width, and intensity fluctuations of the compressed X-ray pulse compared to the case with no compression. (9 References).
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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: 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: Status and initial commissioning of a high gain 800 nm SASE FEL
format: conference proceeding
conference: FEL 1999 21st
year: 2000
22 authors: A. Tremaine | Pedro Frigola | A. Murokh | P. Musumeci | C. Pellegrini | J.B. Rosenzweig | M. Babzien | Ben-Zvi, I. | E. Johnson | R. Malone | G. Rakowsky | Skaritka, J. | X.J. Wang | Yu, L. H. | Van Bibber, K. A. | J.M. Hill | G.P. Le Sage | R. Carr | M. Cornacchia | Nuhn, H. D. | Ruland, R. | D. C. Nguyen
abstract: We describe the status and initial commissioning of the visible to infrared SASE amplifier (VISA) experiment. VISA uses a strong focusing 4 m undulator, the Brookhaven National Laboratory ATF linac with an energy of 72 MeV, and a photoinjector electron source. The VISA fundamental radiation wavelength is near 800 nm and the power expected at saturation is near 60 MW. Power, angular and spectral measurements are planned for the VISA radiation and these results will be analyzed and compared with SASE FEL theory and computer simulation. In addition, the induced electron beam micro-bunching will be measured using coherent transition radiation. (12 References).
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title: The Drive Laser for the APS LEUTL FEL RF Photoinjector
format: conference proceeding
conference: FEL 1999 21st
year: 2000
3 authors: G. Travish | N. D. Arnold | R. J. Koldenhoven
abstract: The APS LEUTL free-electron laser (FEL) is a high-gain, short-wavelength device requiring a high-current, low-emittance beam. An rf photoinjector driven by a laser is used to provide the requisite beam. The drive laser consists of a diode-pumped Nd:Glass oscillator and a chirped pulse amplification (CPA) system consisting of a grating stretcher, a flashlamp-pumped Nd:Glass regenerative amplifier, and a grating compressor. The system generates 4-mJ pulses in the IR with a pulse length as short as 2 ps FWHM and a repetition rate of 6 Hz. Nonlinear doubling crystals are used to generate fourth-harmonic output of ~500 uJ in the UV (263 nm), which is required to exceed the work function of the copper cathode in the gun. This paper describes the drive laser as well as the extensive controls implemented to allow for remote operation and monitoring. Performance measurements as well as the operating experience are presented.
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