Multiple ionization characteristics of hall thruster with large height–radius ratio and their effects

Increasing the specific impulse has become one of the main trends in the development of Hall thrusters and may be achieved by increasing the proportion of multiply charged ions in the plume. In this study, the multiple ionization characteristics of Hall thrusters with large height–radius ratios and their effects on the specific impulse and other performance parameters were examined via numerical simulations. The simulation results show that the proportion of multiply charged ions in a Hall thruster with a large height–radius ratio increases by 7.8 percentage points, compared with that of the traditional Hall thruster, and the multiply charged ions can obtain a higher average jet velocity under an accelerating voltage, thereby improving the specific impulse and thrust of the thruster. Further analyses show that a structure with a large height–radius ratio reduces the cooling effect of the channel wall on the electrons, and the increase in electron temperature effectively promotes the occurrence of the multiple ionization process. In addition, the smaller wall area and the larger magnetic field intensity in the near-wall region inhibit the electron near-wall conduction and prevent the potential negative effect of the increase in electron current caused by multiply charged ionization, which ensures a high level of efficiency. It was proved that multiple ionizations contribute positively to the specific impulse and efficiency of Hall thrusters with a large height–radius ratio. This serves as a reference for the high specific impulse design of Hall thrusters with large height–radius ratios and provides a new optimization perspective for improving the specific impulse of Hall thrusters.