| Travelling-wave tube(TWT)is an important vacuum electronic device widely used in radar,electronic countermeasures and communication systems。The electron optical system of the TWT is used to control the generation,focusing,and collection of electron beam.The design and manufacture of electron optical system is essential to the performance of TWT.With higher frequency of TWT,the size of the high-frequency structure is reduced,the radius of the electron beam interacting with the high-frequency field is reduced,and the current density is increased,which makes the design of the electron optical system more difficult.High precision electron optical simulation software greatly improves the working performance and manufacturing efficiency of TWT.MTSS,a dedicated design software suit for microwave tubes developed by University of Electronic Science and Technology of China,can carry out comprehensive,fast and accurate simulation of TWT.MTSS-EOS is a dedicated electron optical design software,MTSS-MFS is a dedicated permanent magnetic focusing system design software.It is of great engineering value to use MTSS to design high performance electron optical system for TWT and to propose a design method to improve the device performance and design efficiency,as well as to summarize relevant design experience.From the perspective of engineering,we focus on the study of simulation technology of high-performance electron optical system.The main work and innovations of the thesis are as follows:(1)In the simulation design of electron gun,a fast design method of high-performance electron gun based on MTSS-EOS is proposed,which improves the performance and design efficiency of electron gun.,At the same time,based on the research of the thermal emission numerical model,the defects of the spherical-constraint model about thermal initial velocity in MTSS-EOS were found,and the software was further improved.(2)In the simulation design of collector,the optimization method of the highly recyclable electron beam at the entrance of the collector is studied.This method is helpful to further improve the total efficiency.The design experience of performance improvement of the collector was summarized,in which a claw-shaped collector structure was proposed,which can effectively suppress secondary electrons and reduce reflow.(3)In the simulation design of magnetic system,realize the fast and accurate design of PPM focus system by combining the analytical and numerical solutions of the magnetic field.The electron beam is well focused by PPM magnetic focusing system.The influence of magnetic field in electron gun transition zone on transmission of electron beam is also analyzed.(4)Based on the research of the simulation technology of electron optical system,the electron optical system of a Ku-band TWT is designed,and the measured total efficiency is greater than 67%.The electron optical system of an L-band TWT is designed and the measured total efficiency is greater than 67%.The comparison of simulation and test data verifies the effectiveness of the high-performance electron optical system simulation technology proposed in this thesis.Finally,a Ka-band TWT electron gun is designed with the design requirements are fully satisfied. |
