Research On Optimization Method Of High Compression Ratio Sheet Beam Electron Gun

Currently,as the microwave tube operating frequency increases,the size of the structure of the wave-injection interaction gradually decreases.In order to maintain the same output power and current,the size of the electron injection will be reduced accordingly leading to an increase in current density,making the velocity dispersion within the electron channel increase,while requiring a magnetically larger focusing magnetic field.The band injection device is a good solution to the current problems of the ring and cylindrical electron injection in high current and high frequency band operation.Sheet beam has the characteristics of high current,high current density,and low cathode current emission density.The sheet beam electron gun as an important part of the sheet beam microwave device,currently there are mainly optimization relies on manual,low automation optimization problems,and at the same time with the sheet beam electron gun compression ratio increases,the optimization difficulty is gradually increased.In this thesis,the cathode and the focusing electrode are designed based on the Pierce electron gun using the spline design,and the joint simulation of CST and MATLAB is established.The influence of the main structural parameters of the sheet beam electron gun on the beam shape is studied,and the superior and inferior performance of the electron gun is also analyzed and studied,which paves the way for the design of the optimization procedure.In this thesis,an optimization procedure based on fuzzy control is designed,and a rule base based on human optimization experience is designed to achieve automatic design and optimization of sheet beam electron guns with single-sided compression ratios of 20 and 30,which can be approached quickly and accurately to the correct value compared to genetic algorithm.The program was used to design a sheet beam electron gun with single-sided compression ratios of 40 and 50,and to design a sheet beam electron gun with current boosts up to 0.4 A and 0.6 A based on a sheet beam electron gun with a single-sided compression ratio of 30.The characteristics of the sheet beam guns were investigated in the case of high compression ratios and high currents,and the problems that occurred in the design.Sensitivity analysis of the assembly error of the high compression ratio sheet beam electron gun,with the increase of the compression ratio,the cathode,focusing pole and other structural dimensions become larger making the impact of the assembly error weakened.Based on the new cathode structure,we designed a new bilateral compression sheet beam electron gun,by increasing the broadside compression,exponentially increase the cathode emission area and thus achieve a high compression ratio,where the broadside compression ratio is 3:1 and the narrowside compression ratio is 17:1.The size of sheet beam at the waist position is 1.23mm×0.20 mm,which has good laminar flow at the injection waist position.The cathode emission area reaches 9.68 mm~2 and the actual current emission density is 2.12 A/cm~2.The smaller current density can effectively improve the lifetime of the cathode.