Study On Discharge Characteristics Under Different Voltages Of Hall Effect Thrusters

The Hall Effect Thruster (HET) is a kind of electric propulsion devices which ismature both in theory and application. The advantages of HET are simple structure, highspecific impulse, efficiency and reliability. With the development of long life satelliteplatform and deep space exploitation, high specific impulse becomes an importantdirection of development of HET. It has been proved by theory and experiments that thespecific impulse can be increased by increasing discharge voltage. However, it has alsobeen found in experiments that under high discharge voltage, the dischargecharacteristics of HET changes obviously. The main phenomena are “electrontemperature saturation” when increasing discharge voltage without changing magneticfield, and “electron current increase under high discharge voltage” when adjustingmagnetic field to discharge voltages. This thesis starts with these two phenomena, andvary-discharge-voltage HET discharge characteristics are researched in detail.First of all, based on the application background and actual demand ofvary-discharge-voltage operation of HET, vary-discharge-voltage characteristics isresearched in detail experimentally in this thesis with comparison to foreignexperimental research. The experimental characteristics of HET under two kinds ofvary-discharge-voltage operating mode (with and without changing magnetic field) aresummarized and compared. Experimental foundation for theoretical analysis is built.PIC simulation, which is based on the fundamental physical processes andstatistical methods, is the main method of HET numerical simulation. By using thismethod, qualitative simulation to the experimental phenomena is performed. Thesimulation results show that, without changing magnetic field, the magnetic fieldadjusted under low discharge voltage cannot satisfy high voltage operation requirements.Meanwhile, a sudden change of the parameters in discharge channel occurs whenincreasing discharge voltage. With adjusting the magnetic field strength, the suddenchange disappears and high voltage operation range is broadened.After the contents above, the factors affect electron temperature and electroncurrent are analyzed. Furthermore, the mechanisms lead to the “electron temperature saturation” and “electron current increase” are analyzed by using PIC simulation results.Finally, the thesis points out the effect of magnetic field strength on high dischargevoltage operation of HET. The two directions of high voltage optimization, which areadjusting magnetic field topology with increasing magnetic field strength and changingwall materials without increasing magnetic field strength, are proposed.At last, based on theoretical analysis of the control mechanism of magnetic field toion transportation, high voltage optimization based on magnetic field adjustment isaccomplished by this thesis. The mechanism of magnetic field optimization is analyzedby using PIC simulation method. The direction of magnetic field optimizationadjustment under high discharge voltage is proposed. Meanwhile, fundamental researchof changing wall materials under high voltage is carried out, and the research directionof wall material under high voltage is determined.