Analysis and simulation of radial electron beam transmission under non-immersed magnetic field

摘要

The non-immersed focusing of radial electron beam is investigated by theoretical analysis and PIC simulation. Under the condition of thermionic emission and diode voltage is 2kV, the operation mode of coaxial foilless diode with focusing electrode changes from emission capacity limited into space charge limited. The I-V relationship and electrostatic beam trajectory of the diode are obtained by simulation. Combining with single-electron theory and Poisson equation, the motion state and Brillouin magnetic field expression of the radial electron beam is analyzed theoretically. Under the condition of diode voltage is 2kV and current is 0.5A, the radial electron beam achieves steady trajectory when the external magnetic field is 0.04T. The beam width basically remains 0.5mm in a certain range of 30mm. The simulation results demonstrate that the influence of magnetic field distribution in transition region on beam transmission is obviously.