Regularities and mechanisms of development of instabilities in the system with intense relativistic electron beam

We have investigated analytically and numerically the development and interaction of Bursian/Pierce and diocotron instabilities in a relativistic electron beam propagating in a cylindrical drift chamber, depending on the beam geometry, current and the magnitude of the external uniform magnetic field. We have found out that the interaction of instabilities results in the formation of a virtual cathode with a complicated rotating helical (vortex) structure and several reflection regions (electron bunches) in the azimuthal direction. We have shown shown that the number of electron bunches in the azimuthal direction depends on the system parameters. We have discovered the connection between the number of bunches and the generation frequency.