Influence of the secondary electrons on the space charge oscillations in the gyrotron adiabatic trap

Abstract

One of the characteristic features of magnetron injection guns (MIGs) forming intense helical electron beams (HEB) is the trapped magnetic field distribution and, therefore, some of the electrons with the greatest oscillatory velocities are reflected from the magnetic mirror, becoming locked into the adiabatic trap between the cathode and cavity. The trapped electrons (TE) degrade the helical electron beam quality and can initiate beam instability in some regimes. In this work the influence of TE on the beam parameters is considered. The numerical simulation of HEBs was carried out on the basis of the PIC-method within the quasi-static model of the electric field. The self-consistent beam magnetic field was not taken into account. The numerical simulation was carried out taking into account the initial azimuthal velocity spread on the cathode, which allows one to consider the joint action of the emitting surface roughness and the thermal velocities of the electrons.