Modeling of a planar FEL amplifier with a sheet relativistic electron beam

The paper is devoted to the modeling of a 75 GHz planar FEL-amplifier. This amplifier is driven by a sheet electron beam (1 MeV, 2 kA) produced by the U-3 accelerator (BINP). Different approaches based on non-averaged self-consistent system of equations as well as the averaged equations were used for the description of interaction between the electron beam and the TEM-mode of the planar waveguide. Both methods demonstrated similar results with maximum gains 24–25 db, corresponding to an output power of about 250–300 MW and an efficiency of 14–17%. The 2-D version of the PIC-code KARAT was used for additional modeling. KARAT-based simulations demonstrated a maximum gain up to 22 db, output power 160–170 MW and an efficiency of 9%. The reduction of gain can be explained by the space-charge effects.