An Axial Output Relativistic Magnetron Fed by a Split Cathode and Magnetically Insulated by a Low-Power Solenoid

Abstract

One of the main difficulties in designing a relativistic magnetron producing high-power microwaves (HPMs) to be compact, is the power source required to feed the solenoid producing the axial magnetic field, which magnetically insulates the electron beam. This is because the diffusion of the magnetic field through the walls of the system is on the millisecond timescale. The latter requires high-power supplies and restricts the magnetron from operating repetitively. Using permanent magnets instead does not make the system sufficiently compact, because of the size and weight of the magnets and does not allow varying the magnetic field. We suggest a simple solution to this problem by cutting longitudinal slits through the entire magnetron anode system. With such slits, the magnetic field penetration is not restricted by the diffusion rate. Thus, one can apply a microsecond-timescale magnetic field produced by a solenoid powered by a considerably smaller power supply. We test this idea by using particle-in-cell (PIC) simulations of a magnetron for the axial output design suggested by Xu et al. (2018) fed by a split cathode (Leopold et al. , 2020). With a split cathode, the second major problem with relativistic magnetrons is alleviated—pulse shortening is avoided.