Research On Neutralizing Electron Source Of Micro Ion Thruster

With the vigorous development of microsatellite technology in various countries around the world,researchers' requirements for the performance,life and reliability of microsatellite propulsion systems have gradually increased.Electric propellers have become a research hotspot in the field of spacecraft technology in various countries.The neutralizer is an important part of the electric propulsion system.the neutralizer electron source of the micro-electric propulsion system must have low power consumption,strong anti-pollution capability and good electron emission performance.In recent years,the use of hollow cathodes as electron sources for neutralizers has been a research hotspot.However,the hollow cathode is obviously not suitable for the electric propulsion system of the microsatellite.The main reason is that the hollow cathode consumes too much power,has a high operating temperature,and is overloaded.The oxide cathode has the advantages of low operating temperature,low power consumption,and high emission current density,and fully meets the requirements of the micro thruster and the electron source to the cathode material.This thesis proposes a neutralization electron source design with small volume,low power consumption,high current density and strong anti-pollution capability.Using the oxide cathode as the cathode material of the neutralization electron source,the focusing pole,the accelerating pole and the magnetic deflection system were designed.The simulation experiment of the neutralization electron source was made by using OPERA-3D computer simulation software,and the structure was optimized by continuously adjusting the design scheme.The parameters ultimately lead to the best design.After the completion of the neutralization electron source processing,the thesis also tested the electron emission capability of the neutralization electron source.The main contents and conclusions are as follows:(1)Structural design and optimization of neutralization electron sources.In order to meet the requirements of micro-electric thrusters,the thesis design and optimization of the electron optical system consisting of cathode,focusing electrode,accelerating pole and magnetic deflection system,makes the neutralization electron source fully neutralize the plume of the electric thruster under the conditions of small volume and low power consumption.At the same time,the electron optical system can block external pollutants from bombarding the cathode surface and improve the anti-pollution ability of the neutralizing electron source.(2)Preparation of the cathode.The cathode prepared herein is an oxide cathode which has a low operating temperature and low power consumption.The prepared oxide cathode is electrically activated,and when the cathode heating power after activation is 1 W,the emission current can reach 1 mA or more.In order to make up for the deficiency of the oxide cathode,the power consumption of the cathode is minimized.In this thesis,the field emission cathode is used instead of the oxide cathode to supply the electron beam to the neutralization electron source.The polycrystalline LaB6 field emission cathode is prepared and the cathode is fabricated and carried out corresponding test.(3)Research on emission performance of neutralization electron source.According to the calculation results of the simulation software,we made structural design,part processing,test circuit assembly and final device testing on the electrodes and other components of the micro ion thruster and the electron source.Finally,through the test of the electron source,with an anode volte of 600 V,emission current of about 1 mA,electron beam deflection angle of nearly ninety degrees,the micro-ion thruster neutralizing electron source with an overall size of less than 30 mm were obtained.