Powerful Long-Pulse Bragg FEL of Sub-THz to THz-band: Simulations and Tests of Electrodynamic System

Project of high-power long-pulse FEL operating from sub-THz to THz-band is initiated in collaboration between BINP RAS (Novosibirsk) and IAP RAS (N.Novgorod) based on the linac “LIU” 5 - 20 MeV/2 kA/200 ns of the new generation. The aim of this project is to achieve a record sub-GW power level and pulse energy content up to 10 - 100 J at THz frequencies. An advanced Bragg resonator based on coupling of propagating and quasi-cutoff waves and capable to provide stable narrow-band generation in strongly oversized interaction space is one of the key components of this FEL. Proof-of-principle operation of FEL with the resonator of such type has been already demonstrated up to W-band and narrow band generation at multi-MW power level has been observed for the transverse oversize factor (diameter) of ~ 5 wavelengths. The paper presents design parameters, results of simulations and “cold” tests of electrodynamic system for FELs operating from 300 GHz to 600 GHz under the oversize factor of ~ 20 and higher.