Author: Hemsing, E.
Paper Title Page
MOP075 Laser Seeding Schemes for Soft X-rays at LCLS-II 223
  • G. Penn
    LBNL, Berkeley, California, USA
  • P. Emma, E. Hemsing, G. Marcus, T.O. Raubenheimer, L. Wang
    SLAC, Menlo Park, California, USA
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract Nos. DE-AC02-05CH11231 and DE-AC02-76SF00515.
The initial design for LCLS-II incorporates both SASE and self-seeded configurations. Increased stability and/or coherence than is possible with either configuration may be provided by seeding with external lasers followed by one or more stages of harmonic generation, especially in the soft x-ray regime. External seeding also allows for increased flexibility, for example the ability to quickly vary the pulse duration. Studies of schemes based on high-gain harmonic generation and echo-enabled harmonic generation are presented, including realistic electron distributions based on tracking through the injector and linac.
Correlated Energy Spread Removal with Space Charge for High Gain Harmonic Generation  
  • E. Hemsing, G. Marcus, A. Marinelli
    SLAC, Menlo Park, California, USA
  • D. Xiang
    Shanghai Jiao Tong University, Shanghai, People's Republic of China
  We study the effect of longitudinal space charge on the correlated energy spread of a relativistic beam that has been microbunched for the emission of coherent, high harmonic radiation. We show that, in the case of microbunching induced by a laser modulator followed by a dispersive chicane, longitudinal space charge forces can act to significantly reduce the induced energy spread of the beam without a reduction in the harmonic bunching content. This effect may be optimized to significantly increase the harmonic number achievable in seeded HGHG free electrons lasers, which are otherwise limited by the induced energy spread from the laser.
The work presented here has been published in Reference [1].
[1] E. Hemsing et al., to appear in Phys. Rev. Lett. (2014)
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