Study on the characteristics of non-Maxwellian magnetized sheath in Hall thruster acceleration region

摘要

The secondary electron emission(SEE) and inclined magnetic field are typical features at the channel wall of the Hall thruster acceleration region(AR), and the characteristics of the magnetized sheath have a significant effect on the radial potential distribution, ion radial acceleration and wall erosion. In this work, the magnetohydrodynamics model is used to study the characteristics of the magnetized sheath with SEE in the AR of Hall thruster. The electrons are assumed to obey non-extensive distribution, the ions and secondary electrons are magnetized.Based on the Sagdeev potential, the modified Bohm criterion is derived, and the influences of the non-extensive parameter and magnetic field on the AR sheath structure and parameters are discussed. Results show that, with the decrease of the parameter q, the high-energy electron leads to an increase of the potential drop in the sheath, and the sheath thickness expands accordingly,the kinetic energy rises when ions reach the wall, which can aggravate the wall erosion.Increasing the magnetic field inclination angle in the AR of the Hall thruster, the Lorenz force along the x direction acting as a resistance decelerating ions becomes larger which can reduce the wall erosion, while the strength of magnetic field in the AR has little effect on Bohm criterion and wall potential. The propellant type also has a certain effect on the values of wall potential,secondary electron number density and sheath thickness.