<title>High-power microwave generator based on a relativistic BWO</title>

Abstract

Recent backward wave oscillator (BWO) studies show the importance of the reflected forward traveling wave, end reflections, and the initial phase difference between backward propagating waves on microwave generation efficiency. A high power microwave generator using efficient interaction of a relativistic electron beam with backward and fast forward waves was investigated both theoretically and experimentally and is described in this paper. The effects of variations in phase velocities on BWO efficiency was also investigated. Theory predicts efficiencies of 35-40% for uniform and up to 60% for nonuniform slow wave structures (SWSs), in the absence of beam space charge. Furthermore, it was found that the interaction with the forward wave and the SWS inhomogeneity can counter the effect of beam space charge in reducing BWO efficiency. Experiments were performed using 'Sinus' family relativistic electron beam accelerators. Uniform relativistic BWOs with microwave power exceeding 650 MW at a radiation efficiency of 30% were achieved. Efficiencies of nonuniform BWOs reached 40% with corresponding microwave powers of 500 MW.