Novel type of intense electron optics system for Ka-band klystron

A novel type of the electron gun, with a high compression ratio and with a π-shaped focusing permanent-magnet, was designed for Ka-band klystron by modifying the axial symmetric Pierce electron gun. The electron beam trajectory and cathode emission behavior of the novel electron gun were theoretically analyzed and numerically simulated with software CST and EGUN to optimize the structure and estimate the voltage withstanding capacity. The transmission of the electron beam in the uniform focusing magnetic field was mathematically modeled and numerically simulated with EGUN and MAGIC codes. The simulated results show that the newly-designed electron gun has a compression ratio of about 51, a perveance of 0.6 μP and a range over 8 mm, when operating at 14 kV with an emission current density below 12 A/cm2, and that the highly compressed electron beam smoothly passes the interaction zone with little spreading, possibly because the focusing magnetic field effectively reduces Coulomb correlation of electrons in the beam. © 2015, Science Press. All right reserved.