Rotating spoke analysis of Hall thruster performance during the extinguishing process

Hall thrusters must be frequently ignited and extinguished during operation in orbit. The thruster is typically extinguished by terminating the anode voltage. However, the equilibrium state of the plasma in the discharge channel is lost when the external electric field disappears. This consequently changes the state of the plasma, causing rotating spokes to appear. However, spoke rotation ceases after nine rotations. Therefore, in this study, a high-speed camera was used to study the instantaneous spoke rotations of a Hall thruster during the extinguishing process. Additionally, the characteristics of the azimuthal rotating spoke during this process were studied. It was found that, because the anode voltage does not instantaneously decrease to 0 V during the extinguishing process, the spoke mode changes from multi-mode to single-mode. Furthermore, as the voltage dropped from 250 to 0 V, a single-mode spoke appeared, and the spoke speed linearly decreased.