Characteristics and suppression methods of low-frequency oscillation in Hall thruster

Low frequency oscillation in the discharge channel of Hall thruster is an important physical phenomenon that affects its performance and stability. In this paper, the characteristics of low-frequency oscillation of the discharge current of Hall thruster and its suppression method are numerically studied by using a onedimensional fluid model. Assuming that the discharge channel satisfies the quasi-neutral condition, the effects of electron-neutral collision, electron anomalous transport and electron-wall collision on conductivity are considered. The changes of plasma parameters and the effects of magnetic field, preionization rate, and atomic velocity on the amplitude and frequency of discharge current oscillation are also studied. Research results show that the variation of electron temperature in the discharge channel is closely related to the ionization process, and the electron temperature increases as the ionization intensity increases. The fluctuations in neutral gas flow rate and atomic density in the discharge process cause the ionization region to move forward and backward and the ionization intensity to change, which are the main driving forces for the low-frequency oscillation of discharge current in the channel. The magnetic field intensity in the discharge channel affects the axial current by influencing the electron mobility. With the increase of field strength, the oscillation frequency of current decreases, and under different magnetic field strengths, the current amplitude drops as the discharge voltage decreases. When the preionization rate of the working gas increases to above 4%, the amplitude of the discharge current oscillation gradually decreases. When the preionization rate is greater than 3% and the atomic velocity is less than 160 m/s, the discharge current oscillation in the channel exhibits damping attenuation, achieving a stabilizing effect which conduces to stabilizing the discharge of the Hall thruster.