Simulation of a high-gain tapered-wiggler free-electron laser

Results from a numerical model of a high gain (electron-beam power input laser beam power) FEL amplifier are presented. A number of two dimensional effects must be considered in an FEL amplifier design. In many tapered wiggler designs, the wiggler length may be a half dozen or more Rayleigh lengths Z sub R and thus diffraction losses will play an important role. As the laser beam propagates in the longitudinal direction Z, the beam spreads out radially, thus lessening the depth of the pondermotive well (or "buckets') in which trapped electrons execute their synchroton motion.