Review of studies of superradiative microwave generation in X band and Ka band relativistic BWOs

This paper presents a review of recent studies of superradiant (SR) regime of high-power microwave generation of relativistic backward-wave tubes. The fundamental possibility of producing microwave pulses with peak power substantially exceeding the driving electron beam power was demonstrated in theory and simulation. In experiments, beam-to-microwaves power conversion factors of 1.5 in the Ka band and up to 1.8 in the X band were achieved. High-efficiency Ka band generation was obtained at a low B field (2 T) below the cyclotron resonance. With the use of a dc solenoid, SR pulses were generated in a batch mode at a pulse repetition frequency of 1000-3500 Hz.