Powerful 60 GHz FEM with advanced Bragg resonator

Project of powerful FEM operating from Ka- to W-band and aimed to accelerating applications is developed in collaboration between JINR (Dubna) and IAP RAS (N. Novgorod) based on linac LIU-3000. The key components to advance the JINR-IAP FEM into short wavelengths are short-period tapered wiggler, which is responsible for high-quality helical electron beam formation, and advanced Bragg resonator with feedback loop including quasi-cutoff wave, which improves selectivity of the resonators over transverse coordinates and allows of the FEM operation with strongly transverse oversize of the interaction space. Present paper describes recent results on the FEM-oscillator at 60 GHz frequency range. In the proof-of-principal experiment narrow-band excitation of the FEM with multi-megawatt power level and the frequency belonging to designed feedback loop of the Bragg resonator was obtained.