High-Efficiency, Magnetized, Virtual-Cathode Microwave Generator

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Abstract
Microwave generation by electron beams in virtual-cathode configurations can achieve significant power levels. However, most designs inherently have two competing mechanisms generating microwaves: the oscillating virtual cathode and the reflexing electrons. These mechanisms interfere destructively with each other. This paper reports investigation of a novel idea of using an external axial magnetic field and a thick anode with an appropriate collimating slot to extract the electron beam and to suppress the reflexing electrons. It was found that high-power, narrow-band, monochromatic microwaves could be generated with efficiency of 10% to 20%.