Increase of generation frequency of relativistic electron beam with virtual cathode using the regimes with the developed instabilities

We report on the physical mechanisms of development, coexistence and interaction of Pierce-Bursian and diocotron instabilities in the non-neutral relativistic electron beam (REB) and their influence on generation characteristics in the classic vircator. The analytical and numerical analysis is provided by means of 3D electromagnetic simulation. We conducted an extensive study of characteristic regimes of REB dynamics determined by the instabilities development. As a result, a regime map has been obtained. It demonstrates sequential switching of the REB dynamics from the regime with 1 to the regime with 7 electron bunches in the azimuth direction with the beam current growth for the different external magnetic fields. We discovered the connection between the number of bunches and the generation frequency.