Research On Reliability Of Spindt Cathode For Electric Propulsion Neutralizer

Nowadays,the satellite system is developing towards lightweight and miniaturization.As the trend of satellite development in the future,micro nano satellites have been widely concerned by researchers all over the world.Electric propulsion,known as the heart of micro nano satellite,is the key technology to promote the development of micro nano satellite technology.The electric propulsion neutralizer is an important device in the whole electric propulsion system.Scientific research can effectively solve the problems of plume pollution.At present,the widely used electron sources include tungsten barium cathode and lanthanum hexaboride hollow cathode.These cathodes as electron sources have some problems,such as difficult miniaturization of device structure and high energy consumption.The emergence of field emission cathode has brought a glimmer of dawn to solve these problems.Compared with hot cathode and hollow cathode,Spindt cathode has great potential as field emission cathode.As far as Spindt cathode is concerned,the most urgent problem is how to improve the reliability of emission current.For reliability,improving the shape of the launcher and reducing the difference of the sharp cone are two important aspects.This paper starts with the improvement of resistive layer and sacrificial layer.By studying the sacrificial layer technology to achieve the best emitter shape;By adding a resistive layer,it can cut off the abnormal emission of a single sharp cone.The work of this paper is as follows:1.The structure of the resistance layer is designed,the material of the resistance layer is studied,and the parameters of the resistance layer are determined.In this paper,we use the resistance variable layer structure of Cu-SiO₂,and conduct experiments on the thickness of SiO₂layer and Cu layer thickness.The resistance voltage increases with the increase of SiO₂layer thickness;The increase of Cu layer thickness can significantly increase the voltage required by resistance transformer,but also reduce the current.Finally,the best process parameters are obtained,that is,the thickness of SiO₂is 100～200 nm and the thickness of Cu layer is 200 nm.2.The material and technology of sacrificial layer are studied.Finally,aluminum is used as the sacrificial layer material,which is prepared by oblique vapor barrier method.Among them,the evaporation angle and evaporation amount were experimentally explored.If the evaporation angle is too small,the height of the sharp cone will be affected,and if the evaporation angle is too large,the sharp cone will not be sharp;Too much aluminum will also affect the height of the sharp cone.The final process parameters are that the amount of evaporation is 0.35 g and the evaporation angle is 58°.3.We built the test device,tested the spindt cathode with or without resistive layer,and drew the I-V characteristic curve,F-N characteristic curve and stability curve.The results show that the cathode with resistive layer has a smaller opening electric field（about 6.6×10~4V/m）,larger emission current（about 1 m A）and stronger stability（the current fluctuation range is only 10%under long-time test）.