Simulation Research On Output Characteristics Of Hollow Cathode Electron Gun

The hollow cathode electron gun has the advantages of large emission current,high current density,self-focusing electron beam and simple structure.These advantages make it have great potential in the application of millimeter wave and terahertz microwave source devices.At present,the research on hollow cathode electron gun at home and abroad can be mainly divided into computer simulation and experiment.From the experimental point of view,the measurable physical quantity of the experiment is extremely limited,and it is difficult to directly reflect the evolution of the plasma in the hollow cathode.However,the numerical simulation method of plasma can conveniently obtain the evolution process of the plasma and the state of the electron beam.In this thesis,the output characteristics of the hollow cathode electron gun was studied by numerical simulation.The output characteristics of the hollow cathode electron gun include electron beam current,beam density,and beam velocity distribution.These characteristics had a substantial effect on the performance of microwave vacuum electronic devices.This thesis consists of three parts.In the first part,a three-dimensional simulation model of a single-gap hollow cathode electron gun was established through the particle model of Vorpal software.Based on the simulation results,the spatial distribution of the potential,charged particle density and average velocity of the charged particles varying with time were obtained.After analyzing the evolution process of these physical quantities,the basic principle of hollow cathode discharge was obtained,which laid the foundation for the subsequent researches.In the second part,a series of hollow cathode electron guns under various operating conditions were simulated.Firstly,through data statistics,the characteristics of the beam velocity distribution were obtained.After modeling and analyzing,it was found that the beam velocity distribution was close to the Poisson distribution.Then we obtained the variation trend of the beam velocity distribution with time,we found that the difference of the beam velocity distribution at different moments was obvious.We also obtained the characteristics of the beam density distribution and its variation trend with time.Finally,the effects of various operating conditions(gas pressure,potential difference between cathode and anode,cathode aperture)on the beam current and velocity distribution were studied.In the third part,a single-gap hollow cathode electron gun with sheet electron beam was simulated.In the same way,we obtained the evolution of the discharge,and we analyzed the effect of the rectangular cathode hole.Through data statistics,the variation trend of the density and velocity distribution of the sheet electron beam with time were also obtained.Through the research works of this thesis,we understood the output characteristics of the hollow cathode electron gun and the effect of various operating conditions on it,which laid the foundation for its further application.