3-Dimensional Simulation Model of Raman Redime Free-Electron Laser

概要

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A model which describes the nonlinear evolution of the radiation field in a high cttrrent Ramanregime free-electron laser with a rectangular waveguide is presented. In the presence of theelectrostatic field (i.e. the plasma wave), although the TE and TM rnodes which are completelyseparated eigen-modes in a vacuum waveguide couple with each other, the coupling is foundto be weak and decoupled by taking the wiggler average. Such weak coupling allows one toderive the equation to deterrnine the electrostatic field which can be solved by introducingthe Gould-Trivelpiece (G-T) mode expansion method. We apply the model to investigate theeffect of space charge on the amplification of the FEL by using a self-focusing wiggler whichhas parabolically shaped pole faces with a relatively low beam energy of around 1 Men. Theelectrostatic field significantly affects the dispersion especially for higher mode nunuber of theradiation. It is found that the electrostatic field makes the resonance condition strict, so thatthe dispersion relation reveals fine structure, reflecting the spatial distribution of the beam andthe 3-dimensional particle motion.
社団法人日本物理学会の論文
1996-12-15