| Among many hypersonic flow field parameter measurement technologies,electron beam fluorescence technology has broad development prospects due to its advantages of non-contact and direct measurement.The electronic gun,as the core component of the technology testing system,is used to provide the required electron beam for testing.The development trend of using electron beam fluorescence technology for flight testing is reflected in the demand for small and lightweight electronic guns.In this paper,based on the application requirements of electron beam fluorescence technology flight test system for electron guns,the advantages and disadvantages of existing electron guns are analyzed and compared,and the design and research of ion bombardment Secondary electrons emission electron guns are carried out by combining theoretical analysis,numerical calculation and experiment.Based on the working principle of electron gun,the electron gun is divided into vacuum system,discharge system and Secondary electrons emission system.The differential vacuum technology,gas discharge,plasma properties and Secondary electrons emission theory involved are analyzed to provide a theoretical basis for the design and simulation of electron gun.Drawing on the design experience of electronic guns both domestically and internationally,and considering factors such as ease of experimental operation,the preliminary design of the electronic gun has been completed.For the required components,the design and selection ideas,basis,and parameters were provided.Use Comsol Multiphysics simulation software to simulate the working characteristics of key components of the electron gun.The influence of the diameter and length of the gas resistance tube on the pressure distribution of the vacuum system was studied using the free molecular flow module of Comsol software;The influence of electrode diameter,ring diameter,height and discharge pressure on the Number density and distribution of positive ions was obtained by using the plasma module of Comsol software;Through the electrostatic module and charged particle tracking module of Comsol software,the influence trend of the radius and spacing of the concave surface of the accelerating cathode on the electrostatic field distribution and the Secondary electrons transmission rate was obtained.A prototype testing platform was built,and the pressure distribution,discharge chamber discharge characteristics,and beam spot parameters of the electron gun vacuum system were obtained through experimental testing.The results show that the designed electron gun vacuum system meets the working needs;By first turning on the high voltage to maintain the gas discharge and then gradually reducing the air pressure,the electron gun discharge chamber can still maintain the gas discharge at the air pressure of 0.7～1.0Pa;In the absence of focusing measures and the installation of an air resistance tube,the maximum beam current of the electron gun reaches 0.95 m A,the maximum acceleration voltage is 20 k V,and the beam spot diameter is about 2-3cm.In this paper,through the research on the design and performance of the ion bombardment Secondary electrons emission electron gun,the important parameters and laws affecting the normal operation of the electron gun are obtained.The experimental results show that the designed electron gun can emit a certain intensity of electron beam,which realizes the verification of the emission principle of the electron gun beam,and lays the foundation for the design and research of the following electron beam focusing and deflection functions. |
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