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FEL 1998 20th

Name: FEL 1998 20th

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Date: 1998-01-01

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Created at: Fri Jul 27 23:53:34 -0700 2007

Updated at: Fri Jul 27 23:53:34 -0700 2007

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6 papers from the conference:

title: The design for the LCLS RF photoinjector
format: conference proceeding
conference: FEL 1998 20th
year: 1999
16 authors: R. Alley | Bharadwaj, V. | Clendenin, J. E. | P. Emma | Fisher, A. | Frisch, J. | Kotseroglou, T. | R. H. Miller | D. T. Palmer | Schmerge, J. F. | Sheppard, J. C. | Woodley, M. | Yeremian, A. D. | J.B. Rosenzweig | D. Meyerhofer | L. Serafini
abstract: We report on the design of the RF photoinjector of the Linac Coherent Light Source. The RF photoinjector is required to produce a single 150 MeV bunch of similar to 1 nC and similar to 100 A peak current at a repetition rate of 120 Hz with a normalized rms transverse emittance of similar to 1 pi mm-mrad. The design employs a 1.6-cell S-band RF gun with an optical spot size at the cathode of a radius of similar to 1 mm and a pulse duration with an rms sigma of similar to 3 ps. The peak RF field at the cathode is 150 MV/m with extraction 57 degrees ahead of the RF peak. A solenoidal field near the cathode allows the compensation of the initial emittance growth by the end of the injection linac. Spatial and temporal shaping of the laser pulse striking the cathode will reduce the compensated emittance even further. Also, to minimize the contribution of the thermal emittance from the cathode surface, while at the same time optimizing the quantum efficiency, the laser wavelength for a Cu cathode should be tunable around 260 nm. Following the injection linac the geometric emittance simply damps linearly with energy growth. PARMELA simulations show that this design will produce the desired normalized emittance, which is about a factor of two lower than has been achieved to date in other systems. In addition to low emittance, we also aim for laser amplitude stability of 1% in the UV and a timing jitter in the electron beam of 0.5 ps rms, which will lead to less than 10% beam intensity fluctuation after the electron bunch is compressed in the main linac.
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title: The VISA FEL Undulator
format: conference proceeding
conference: FEL 1998 20th
year: 1999
14 authors: R. Carr | I. Ben-Zvi | L. Bertolini | M. Cornacchia | P. Emma | Pedro Frigola | E. Johnson | M. Libkind | S. Lidia | H. D. Nuhn | C. Pellegrini | G. Rakowsky | J.B. Rosenzweig | R. Ruland
abstract: The Visible-Infrared SASE Amplifier (VISA) FEL is an experimental device designed to show self amplified spontaneous emission (SASE) to saturation in the 800-600 nm range, where silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is the first SASE FEL designed to saturate, and its diagnostics will provide important checks of theory.
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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: 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: 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: Measured free-electron laser microbunching using coherent transition radiation
format: conference proceeding
conference: FEL 1998 20th
year: 1999
9 authors: A. Tremaine | J.B. Rosenzweig | S. Anderson | Pedro Frigola | M. Hogan | A. Murokh | C. Pellegrini | D. Nguyen | Sheffield, R.
abstract: The microbunch distribution of an electron beam exiting a SASE free-electron laser has been measured using the emitted coherent transition radiation (CTR) produced from a thin aluminum foil placed at the end of the undulator. The wavelength of the coherent transition radiation is shown to be the same as the FEL wavelength, and thus a measure of the beam microbunch spacing. Also, the study of the CTR linewidth and angular acceptance of the radiation captured are shown to be derived from this coherent radiative process. Scattering effects on the forward emitted transition radiation from the electron beam traversing an aluminum foil are also considered. (11 References).
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