• B. Maraghechi, M.H. Rouhani
  AUT, Tehran

Three-dimensional simulation of harmonic up conversion in free electron laser amplifier operating simultaneously with two cold electron beams of different energies is presented in steady-state regime. By using slowly varying envelope approximation, the hyperbolic wave equations can be transformed into parabolic diffusion equations. By applying the source-dependent expansion to these equations, electromagnetic fields are represented in terms of the Hermit Gaussian modes. The electron dynamics is described by the fully three dimensional Lorentz force equation in the presence of a realistic planar magnetostatic wiggler and electromagnetic fields. A set of coupled nonlinear first order differential equations is derived and solved numerically. This set of equation describes self consistently the longitudinal spatial dependence of radiation waists, curvatures, and amplitudes together with the evolution of the electron beam.

• B. Maraghechi, M.H. Rouhani
  AUT, Tehran

One dimensional simulation of Raman free electron laser amplifier with planar wiggler and ion channel guiding is presented. Using Maxwell’s equations and full Lorentz force equation of motion for electron beam, a set of coupled nonlinear differential equations is derived in slowly varying amplitude and wave number approximation and solved numerically. This set of equation describes self consistently the longitudinal dependence of radiation amplitudes, wave numbers, growth rates, space charge amplitudes, and wave numbers together with the evolution of the electron beam. Because of using non-wiggler averaged equation of motion, it is possible to treat the injection of the beam into the wiggler. The electron beam is assumed cold, propagates with a relativistic velocity, ions are assumed immobile and slippage is ignored. The effect of prebunching on saturation can be added to this code. Therefore no driving signal is needed. Ion channel density is varied and the results for group I and II orbits were compared with the absence of ion channel. In contrast to the axial magnetic field, this type of guiding does not produce any drifting motion.