Ion-neutral phasing in Hall thruster breathing mode oscillations

This study uses concurrent spectroscopic measurements that provide evidence of the predator–prey behavior between ions, neutral atoms, and electrons that is theorized to drive the Hall thruster breathing mode, a crucial oscillation in Hall thrusters impacting their efficiency and stability. A novel fast optical emission spectroscopy diagnostic is employed to simultaneously measure the characteristics of neutral and ion populations through their respective emissions. A quasi-1D predator–prey model of the breathing mode is utilized to predict the phase difference between neutral and ion populations according to the predator–prey theory. The observed phase difference between Xe I and Xe II emissions is consistent with the expected phase difference between neutral and ion populations predicted by the quasi-1D model. Several operating conditions are explored, and the impact of adjusting the plasma conditions are explored both through experiments and modeling.