Powerful two-stage THz-range FEL based on intense parallel sheet beams: Design, simulations and recent results

Project of a two-stage cascade THz FEL driven by intense parallel sheet beams is under development at the ELMI accelerator. For powering this two-channel scheme, planar 75 GHz FEM-oscillator with 2D distributed feedback, which was successfully realized in previous experiments, is planned to be used. Pumping wave generated in this first section is transported by the coupling waveguides to the second channel and scattered into the THz radiation at the second parallel electron beam. Results of theoretical analysis, computer simulations and recent experimental studies of this FEL scheme are presented.