| In electric propulsion systems,neutralizers perform a significant and indispensable role,but there are only a few different kinds that can be chosen.Due to its intrinsic benefits,the field emission array cathode has promising development potential in neutralizers.As a result,field emission array cathodes have slowly started to take center stage in neutralizer development.In the structure of neutralizer,the role of grid is also very important.On the one hand,it can help the electric field on the cathode surface become more consistent,on the other hand,the grid can prevent the ion current sprayed by the electric thruster from hitting the cathode surface.Therefore,it is the key to study the influence of various parameters of grid on the overall performance.This thesis is based on the field emission theory,aiming at problems such as short life and poor adhesion between the traditional cathode substrate and the emitter;The current grid has low electron transmission,uneven field strength and irregular cathode grid spacing;In practical application,the preparation cost is high and the process is difficult.The design and test are carried out in combination with opera simulation and the wet corrosion and electrochemical corrosion methods are used for corrosion.Finally,the electronic gun with stable emission current,mass production and low cost is prepared,and its application in neutralizer was finally realized.The main contents of this thesis are as follows:1.Design the cathode,grid and anode structures of electron gun,determine the key parameters.In this thesis,the key parameters of cathode,grid and anode were explored by using Opera-3D simulation software.Finally,appropriate parameters were determined according to the simulation results:(1)the thickness of wedge emitter tip should be reduced to about 0.04 mm,and the thickness of cylindrical emitter tip should be reduced to less than 0.04mm;(2)grid hole diameter: 0.2mm,grid thickness: 0.2mm,grid spacing:-0.2mm;(3)the distance between cathode and anode should be minimized without short circuit.2.Prepare the wedge-type array field emission cathode and test the diode field emission and stability.In this thesis,the wet corrosion process parameters were tested to determine the wet corrosion scheme,and the wedge array field emission cathode was prepared by the wet corrosion process.The minimum thickness of the wedge array emitter tip was 38.18 μm,and the surface morphology was analyzed by SEM characterization.A diode field emission testing device was built to test the field emission and stability of the wedge array field emission cathode.The diode test results show that the maximum field emission current is 39.1 μA and the stability is poor.3 In this thesis,the electrochemical corrosion process parameters were simulated to determine the relevant parameters,and the columnar array field emission cathode was prepared by wet corrosion and electrochemical corrosion process respectively.The minimum tip curvature radius of the columnar array emitter was 7.95 μm,and the surface morphology was analyzed by SEM characterization.A diode and triode field emission testing device are built to test the columnar array field emission cathode.The triode test results show that the maximum field emission current is 7.05 μA,and the stability is good. |
