Design And Optimzation Of Thermal-emission Cathode Without Working Medium Baesd On Coupling Environment

China’s space gravitational wave detection has put forward very high performance and life requirements for electric propulsion,The adjustable precision of 0.1 μN and the service life of 10000 hours require strict control of external interference.The candidate electric propulsion for this mission is generally composed of ion accelerator and cathode electron source.The traditional hollow cathode can not meet the above control requirements due to the need of gas supply,so the cathode without working medium must be used.The main contents are as follows:Firstly,according to the current requirements of the mission,the design and performance test of the thermal emission cathode are carried out.The results show that the cathode has good electron emission characteristics,controllability and stability,which can basically meet the requirements of space gravitational wave detection.On this basis,the coupling discharge test was carried out for the Hall thruster.The results show that the electrons emitted by the hot cathode can not enter the plume region because of the difficulty of electron transmission without the traditional plasma environment,which makes the hot cathode unable to couple with the thruster.Therefore,a new design method must be added to lead out the hot emission electrons,which can neutralize the ions in the plume.In order to solve the problem that electrons are difficult to be extracted,the extraction method of controlling electrons based on touching electrode potential is studied.The discharge characteristics of hot electron emission cathode under different keeper electrode,installation distance and extraction voltage were tested,and the correlation analysis of electron trajectory was carried out.The results show that the keeper electrode aperture has a significant effect on the electron extraction efficiency,and the keeper electrode extraction efficiency is negatively correlated with the maximum extraction current.On this basis,the coupled discharge between the thermal emission cathode and the tangential field Hall thruster is realized by applying the keeper current.The electrons enter into the plume region and neutralize,and the plume potential is reduced and the ion current is extracted.In order to solve the problem that the passing efficiency of thermally emitted electrons is reduced by simply applying the touch and hold voltage,the extraction method of thermally emitted electrons based on magnetic field is studied.The core idea is to use the magnetic field in the hole area of the keeper electrode to reduce the hot electrons fal ing to the keeper electrode and increase the transmittance;The diffusion magnetic field in the plume region is used to diffuse electrons into the plume region and enhance plume neutralization.Both the experimental and simulation results show that the pass rate of hot electron through the keeper electrode is significantly enhanced with the increase of the magnetic field,which reduces the electron emission demand of the hot cathode.On this basis,the magnetic field intensity and magnetic field configuration are optimized,which provides guidance for the subsequent design of thermionic emission cathode.Finally,to meet the requirements of space gravitational wave detection mission,the thermal and mechanical structure of the thermionic emission cathode was analyzed and verified.By adding heat shield,the working temperature of the thermionic emitter is increased significantly,and the heating current and power are reduced effectively;By increasing the fixed support at the emitter,the resistance performance of the thermionic emission cathode can be greatly improved,which provides guidance for the subsequent structural optimization.In addition,based on the analysis of high temperature compatibility of materials in long-term steady state,the thermionic emission cathode has good thermal emission stability.