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TUP049 The Electron Bunch Initial Energy Profile on a Seeded Free Electron Laser Performance FEL, electron, undulator, laser 509
  • J. Wu, A. Chao
    SLAC, Menlo Park, California
  • J. Bisognano
    UW-Madison/SRC, Madison, Wisconsin

Funding: The work of AWC and JW was supported by the US Department of Energy under contract DE-AC02-76SF00515. The work of JB was supported by National Science Foundation Award No. DMR-0537588.
A single-pass high-gain X-ray free electron laser (FEL) calls for a high quality electron bunch. In particular, for a seeded FEL, and for a cascaded harmonic generation (HG) FEL, the electron bunch initial energy profile uniformity is crucial to preserve an FEL narrow bandwidth. After the acceleration, compression, and transport, the electron bunch energy profile entering the undulator can acquire temporal non-uniformity. During the cascading stages, the electron bunch energy profile is also not uniform temporally entering the next stage. We study the effects of the electron bunch initial energy profile on the FEL performance, cascaded HG FEL or single stage FEL amplifier. Concrete examples are discussed for seeded FEL projects being studied.

THP037 RF Design of a Spoke Resonator for High Power Free-Electron Lasers HOM, electron, laser, acceleration 866
  • F.L. Krawczyk, D.C. Nguyen
    LANL, Los Alamos, New Mexico
  • S.J. Cooke
    NRL, Washington, DC
  • B. Rusnak
    LLNL, Livermore, California
  • T.I. Smith
    Stanford University, Stanford, Califormia
  • E.L. Wright
    Beam-Wave Research, Inc., Union City

Funding: Supported by the High-Energy Laser Joint Technology Office
We are investigating spoke resonators that originally were proposed for moderate energy proton acceleration for application in high-average-current free-electron lasers (FEL). This structure holds the promise of alleviating the BBU limitations of conventional rf structures. Spoke resonator have several advantages: 1) strong coupling simplifies the access to higher order modes (HOM), 2) at the same frequency a spoke resonator is about half the size of an elliptical resonator, 3) the spokes provide additional mechanical stability and stiffening , 4) the power and HOM couplers can be attached to the cavity body and do not take up additional space along the length of the accelerator, 5) the presence of the spokes limits the polarizations of the HOMs to two orientations which facilitates the selection of HOM coupler positions. The rf performance of a spoke resonator specifically designed for high-current electron applications (beta=1.0) will be presented and compared with the expected performance of elliptical resonators designed for such applications. Besides the structure's effectiveness for acceleration also HOM properties will be presented.


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