Electric propulsion systems based on Hall thrusters are expanding their applications in space developments. As the size of the satellite decreases, a miniaturized Hall thruster with tens of mN thrust will be required in the near future. However, if the interaction between a discharge channel and the plasma cannot be controlled, the thrust per consumed electric power decreases drastically due to electron cooling, undesirable electron current, and a wide ion beam angle. Therefore, a magnetic field topology should be designed based on principles of plasma physics to prevent plasma–wall interactions.
This dissertation reports on a miniaturized Hall thruster with a high specific impulse and high anode efficiency and analyzes the thruster performance based on particle-in-cell simulation and plasma diagnostics. The average channel diameter and width are 45 mm and 15 mm respec-tively. They were designed with a power consumption of 430 W and a thrust of 20 mN. The miniaturized Hall thruster has a magnetic field topology parallel to the discharge channel and convex towards the anode. This tailored magnetic field topology is difficult to implement in the limited thruster volume and narrow channel width, but this is possible in the miniaturized Hall thruster with the magnetic circuit developed as part of this research.
The tailored magnetic field topology resulted in several desirable effects. Firstly, it formed an ionization region concentrated at the center of the discharge channel. The concentrated ioni-zation can reduce radial ion acceleration inside the channel and enhance the axial ion emission current. In addition, the ionization which is far from anode but not outside the discharge channel reduces the electron current through the anode and increases the xenon propellant ionization. Secondly, the magnetic field tailoring reduces the electron temperature near the channel walls. It decreases the radial ion acceleration as well as the secondary electron emission.
In experiments, these controlled plasma parameters facilitate the enhancement of thruster performance including thrust, specific impulse, and anode efficiency. At a power consumption of 423 W and a xenon propellant mass flow rate of 10 sccm, the thrust, specific impulse, and anode efficiency were 20.7 mN, 2150 s, and 51.6%, respectively. The performance was con-sistent with the results obtained using the plasma diagnosis and multiple charge thrust model. This is an excellent performance which has not been reported for the 200–500 W class Hall thruster.