Research Of Influence And Design Criteria Of Hollow Cathode Key Dimensions

The thesis is about the research of key dimensions of self-heating hollow cathode.Self-heating hollow cathode is an important component of spacecraft electric propulsionsystem, taking on heavy responsibility of providing electron current for plasmadischarge and plume neutralization. Hollow cathode performance and powerconsumption has a significant impact on the propulsion system.Due to the work function of the material, the pressure drop of plasma concentratesin the vicinity of the cathode. The space range of cathode plasma is restricted by sizes ofemitter and orifice, and so plasma ionization, diffusion and other physical processes aresubject to these sizes. Therefore, the sizes of emitter and orifice are critical to thehollow cathode. The design of key dimensions is an important topic of serializationdevelopment of hollow cathode. Experimental and numerical methods are used to studythe key dimensions of hollow cathode in this thesis.In the experimental aspect, a hollow cathode discharge experimental platform isbuilt, including some associated circuitry, piping, procedures, etc. A probe platform isalso designed, which can measure the plasma parameters inside of cathode. In thesimulation aspect, a multi-physics coupling numerical model of hollow cathode isestablished using Comsol. The model includes strongly coupled physical processes suchas plasma discharge, flow and heat transfer, collision reactions between atom, ion andelectron, heating mechanism of plasma on gas and wall, and retardation of ion to flow.Model can fit well with experiments.The hollow cathode emitter size effects and design criteria are studied byexperimental and numerical methods. Through comparison experiments and simulationof emitter size, the relationship between inner diameter of emitter and plasma pre-sheathis found, and design criteria between them is proposed. Internal surface area of emitteris determined according to the material properties and discharge current. The effectivelengthen that plasma can extend in emitter is proposed, and design criteria of emitteraspect ratio is determined on this base.The influence and design criteria of hollow cathode orifice was investigated.Narrower or longer orifice leads to higher inner gas pressure and stronger orificeheating. Gas pressure is more sensitive to diameter than length. As gas pressure is important for pre-sheath parameters, the design criteria of orifice should match that ofemitter. The matching principle of orifice parameters with discharge current wasproposed based on orifice heating effect. The design criteria of hollow cathode life wasproposed, in which it is suggested that under lower discharge current longer orifice andlarger orifice is beneficial, meanwhile a cone hole can compensate the effect of orificeenlargement.