Experimental study on low frequency oscillation in a plume of Hall thrusters

Abstract

In order to study the low frequency oscillation (20–40 kHz) in a plume of Hall thrusters, the plasma parameter oscillations are measured with a Langmuir probe in axial and circumferential directions, and oscillations of different energy ions are measured with a multi-grid probe by varying the potential to repel selected ions. Experimental results indicate that the oscillation of plasma parameters in the plume exhibits the same frequency as a low frequency discharge current oscillation and is synchronous in the circumferential direction at the time scale of the low frequency discharge current oscillation. The time delay of the oscillation in different axial positions is related to the propagation of plasma density along the axial direction. The oscillation of Xe+ has the same frequency as the low frequency discharge current oscillation, but the oscillation of Xe2+ or a high-valence ion is more complex and scattered due to their instability in the ionization process. It is therefore concluded that the low frequency oscillation of plasma parameters in the plume is strongly related to the low frequency discharge current oscillation and the ionization process of a neutral atom.