INVESTIGATIONS OF MAIN MICROWAVE MODE EXCITED BY VIRTUAL CATHODE FORMED BY HOLLOW ELECTRON BEAMS

The process of virtual cathode oscillation exciting microwaves is considered as that of an oscillating current element exciting microwaves. With the approximation of thin charge sheet, the criterion of the main mode of the excited microwave is obtained. The relation between the beam dimension and the output power is discussed. Our criterion is in agreement with that of experiments and particle simulations.