Thermo-mechanical Coupling Characteristic Analysis And Optimal Design Of The Electron Gun Of Travelling Wave Tube

Traveling Wave Tube (TWT) is one of most widly used microwave amplifier. TWT willbe used in many occasions in the future because of its obvious performance advantages.Electron gun is the key component of TWT and also is the “heart” of TWT. The failure rate ofelectron gun accounts for about50%of TWT failure. The gun is the most prone failure partof TWT. So, the reliability of the TWT electron gun not only decides the main factors ofaverage output power of TWT, but also affects the working stability of TWT. The mainfactors causing the gun failure are temperature and vibration, which account for75%offailure rate. Presently, the research on reliability of TWT electron gun are focused on thetemperature distribution of electron gun, the optimum design of key components based on thetemperature and modal analysis of electron gun at room temperature. Only a few scholarsinvoleve in the reliability research of TWT electron gun under the working state (the highesttemperature of the gun will be at1000℃in this state). Therefore, the research on this aspectremains to be further perfected.Considering the small size, complicated structure and high manufacturing cost of TWT,this paper analyze the thermo-mechanical coupling Characteristic of TWT electron gun by theexperiment and finite element method (FEM). Firstly, this paper discusses the basic theory ofphysical properties of materials of TWT electron gun. According to the need of simulationcalculation, parts of experiment results are curve fitting by mathematical methods and originsoftware. And the relation between thermal physical parameters of some materials and thetemperature is obtained. Secondly, the temperature test and temperature field simulation ofTWT electron gun are applied. Compared with simulation and experiment, adjust the finiteelement model, and the average deviation is only6.96%, which shows that the simulationresults are reliable. Based on the adjusted model, research the effect of shadow grid andcontrol grid distance and cathode size change of TWT electron gun on the electric prametersof electron gun. Then, analyze the prestressed modal and random vibtaion of electron gun forthe first time, which is focused on the stress response values, displacement response valuesand acceleration response values of some important connected parts and easy failure parts ofgun. According to analysis, the strength and stiffness weak points of electron gun under the working condition are found. Finally, according to the results of thermo-mechanical couplinganalysis of electron gun, optimize the design of electron gun from two aspects of materialchosen of key parts and structure size change of electron gun.Based on thermal physical properties test and curve fitting of material of electron gun,get the relation between physical properties of some materials and temperature, which enrichthe electric vacuum materials warehouse of electron gun and laid the foundation for thesubsequent reliability research of electron gun in working condition. At the same time, theresults of thermo-mechanical coupling characteristic anlysis and optimization design basedon results of thermo-mechanical coupling analysis can play a role in promoting the reliabilityresearch of domestic TWT electron gun in working condition and guiding TWTmanufacturers to improve the manufacturing process. The analysis results will have a verygood practical guidance.