Generation of higher harmonics in relativistic electron beam with virtual cathode

The study of the generation regimes with intense higher harmonics taking place in a high-power vircator [1] consisting of a relativistic electron beam (REB) with a virtual cathode (VC) has been made. The characteristics of these regimes, in particular, the typical spectra of output signal and their variations with the change of the system parameters (beam current, the induction of external magnetic field) as well as physical processes occurring in the system have been analyzed by means of 3D electromagnetic simulation in CST Particle Studio. The model under study consists of the perfect electric conducting finite-length cylindrical waveguide region (electron beam drift chamber) with the grid electrodes at both ends under the same potential and axially symmetrical at the entrance monoenergetic overcritical annular REB travelling through the drift chamber. Let us note, that the frequency of the fundamental component (the first harmonic) in the spectrum is determined by the value of the disturbed plasma frequency [1].