Author: Fry, A.R.
Paper Title Page
WEP005 Laser Heater Transverse Shaping to Improve Microbunching Suppresion for X-ray FELs 602
  • S. Li
    Stanford University, Stanford, California, USA
  • A.R. Fry, S. Gilevich, Z. Huang, A. Marinelli, D.F. Ratner, J. Robinson
    SLAC, Menlo Park, California, USA
  In X-ray free electron lasers (FELs), a small amount of initial density or energy modulation in the electron beam will be amplified through acceleration and bunch compression process. The undesired microbunching on the electron bunch will increase slice energy spread and degrade the FEL performance. The Linac Coherent Light Source (LCLS) laser heater (LH) system was installed to increase the uncorrelated energy spread in the electron beam in order to suppress the microbunching instability. The distribution of the induced energy spread depends strongly on the transverse profile of the heater laser and has a large effect on the microbunching suppression. In this paper we discuss strategies to shape the laser profile in order to obtain better suppression of microbunching. We present analysis to achieve the Gaussian-like energy spread using a Laguerre-Gaussian laser mode and study the efficiency and alignment tolerance for implementation.  
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