A microwave radiation generator with a virtual cathode and a spherical drift chamber

In the paper we present results of an experimental investigation of a vircator with a spherical drift chamber. The vircator was powered from a generator of high-voltage pulses, making it possible to form electrons beam with energy up to 170 keV and length up to 35 ns on a half height. A front, amplitude and length of the powering high-voltage pulse dependence on microwave radiation pulse power and energy was studied. Significant influence of the electron beam parameters on the vircator efficiency coefficient is shown. A critical current of the electron beam, on reaching of which generation of the microwave radiation starts, is determined. For the spherical chamber it was about 3 kA. Investigation results of spectral characteristics of the vircator radiation are presented. It is shown experimentally that transition from a classical cylindrical drift chamber, having conical horn for radiation output to the atmosphere, to the spherical drift chamber allowed us to increase the power of the microwave radiation in 2.3 times and narrow directional diagram on the level of half power up to the angle of about 12°.