Power of microwave radiation of the relativistic electron beam with virtual cathode in the external magnetic field

Summary form only given. The numerical study of the output power of electromagnetic radiation of the relativistic electron beam (REB) with virtual cathode (VC) in the presence of external transversal magnetic field has been found out with the help of 3D electromagnetic simulation. The model under study consists of the finite-length cylindrical waveguide region (electron beam drift chamber) with grid electrodes at both ends under the same potential and axially symmetrical monoenergetic overcritical REB [1] travelling through the drift chamber. The typical dependencies of the output microwave power of the REB with VC versus external magnetic field have been analyzed and explained in the vircator [1]. It has been shown that the output power of relativistic vircator demonstrates several maxima with external magnetic field growth. The azimuthal instability development under the influence of the beam self-magnetic fields leading to the vortex structure formation in the REB was discovered [2]. It was obtained that the electron beam demonstrates the formation of different vortex electron structures with the growth of the external magnetic field value, in particular, the single, double or triple vortices. Finally, the azimuthal instability is suppressed by the strong external magnetic fields. The azimuthal instability has a considerable influence on the REB critical current [2] and output radiation power of the system [3]. It was found out that the interaction efficiency of the VC in the REB with electromagnetic fields and, consequently, the output power are greater when the beam has no nonuniformities in the azimuthal direction. So, the value of the external magnetic field determined the shape of the formed electron vortex in the system and, hence, its uniformity in the azimuthal direction also determines the value of REB output power and the presence of the local maxima on the dependency of output power versus external magnetic field.