Study of oscillation modeswith intensive higher harmonics in a relativistic electron beam with a virtual cathode

This work presents the results of the study of nonlinear oscillations of a relativistic electron beam with a virtual cathode in the cylindrical drift space depending on external magnetic field values, current and initial energy of injected electrons of the relativistic beam. Special attention was given to the analysis of higher harmonics of fundamental frequency of virtual cathode oscillations with the change of system control parameters. The numerical simulation was carried out by means of CST Particle Studio software package for three-dimensional electromagnetic simulation. The complex dynamics of virtual cathode in the relativistic electron beam were found out. Particularly, these were defined areas in the plane of the control parameters “beam current - magnetic field” where the first/second/third harmonic of current oscillations was maximal.