Analysis of a Hollow Electron Beam Focusing and Transmission

For vacuum electronic devices (VEDs), the use of a hollow electron beam (HEB) increases the beam-wave interaction efficiency and permits a prominent decrease of the cutoff voltage in the focusing-electrode controlled electron gun. To obtain an HEB electron optics system (EOS) with stable propagation, lower ripple, high compression, and good laminarity, the issues related to the HEBs transmission characteristics in a uniform magnetic field are deeply investigated in this article. The studies on the Brillouin flow, which are different from the conclusion of the previous literature, are presented. Through combining the theoretical analysis and the simulation, the distinct motion ways of each layer in the HEB are clearly exhibited in both cases of the immersed flow and the partially shielding flow. This work can provide a meaningful reference for the design of a hollow beam EOS with high transmission and compression.