Experimental Investigation of Plasma Spoke Oscillation Control and Performance Optimization in Planar Hall Thrusters

Recent advancements in micro satellite technology have raised new requirements for propulsion systems, such as high specific impulse and long lifespan. The planar Hall thruster addresses the issue of channel wall erosion during miniaturization by removing the discharge channel and relocating the plasma discharge process outside the thruster, gaining significant attention worldwide. Plasma spoke oscillations during thruster operation greatly influence electron transport, impacting thrust performance and reliability. Understanding spoke oscillation dynamics and its relationship to thruster performance is crucial. Based on the above requirements, a diagnostic system, including a high-speed camera, ion saturation probe, and micro thrust torsional pendulum, was developed for dynamic analysis of plasma spoke oscillations and thruster performance. Proper orthogonal decomposition (POD) and fast Fourier transform (FFT) are used to obtain the main characteristic parameters of spoke oscillations. This study revealed key dynamic characteristics of spoke oscillations, such as frequency and mode proportion, in relation to operating conditions like anode voltage and flow rate. An inherent relationship between the spoke oscillation modes and thruster performance was established and three operating modes were determined based on the plasma oscillation characteristics: rotating spoke mode with stable plasma rotation at low discharge voltage, breathing mode with low-frequency oscillations at high voltage and low neutral flow rate, and transition mode between this two modes. The rotating spoke mode is most conducive to achieving the best thruster performance as it strikes a good balance between key performance parameters, and the anode efficiency can be increased by up to 23.8%. These findings enable performance optimization of planar thrusters and lay the foundation for future control strategies of spoke oscillations.