2ND MANUSCRIPT

ONE-DIMENSIONAL SIMULATION FOR FREE-ELECTRON LASER WITH A RECTANGULAR HYBRID WIGGLE IN THE PRESENCE OF ION CHANNEL GUIDING AND A PREBUNCHED ELECTRON BEAM

Hosseinnezhad, A & Kordbacheh, A
(submitted in the Journal of Plasma Physics)

A one-dimensional nonlinear simulation in a free electron laser containing a square hybrid wiggler with a prebunched electron beam and ion-channel guiding mechanism is studied. A series of coupled non-linear differential equations are derived using the Lorentz equations of motion combined with the Maxwell equations are solved numerically in the framework of slowly varying amplitude and wavenumber. The relativistic electron beam is assumed to be cold, and the self-fields of the electron beam and the slippage of the radiation wave are ignored. The appropriate parameters are chosen so that the Raman regime characterized by large density and low energy is considered. The effect of the prebunched electron beam on the saturation of the device is studied for a variety of ion-channel densities, and the results are compared for groups Ι and ΙΙ orbits. It is found that the ion-channel density increases the saturation of the radiation amplitude for group Ι orbits, whereas the saturated radiation amplitude for group ΙΙ orbits is decreased with increasing the ion-channel density. Moreover, it is found that the saturation length for an FEL with a prebunched beam is considerably larger than that of an uniform electron beam.