Ion-Neutral Population and Electron Temperature Phasing in the Hall Thruster Breathing Mode

This study investigates the breathing mode, a crucial oscillation in Hall thrusters im- pacting their efficiency and stability. Among breathing mode models, a relatively simple 0-D model, the predator-prey model, explains the breathing mode as an interaction be- tween neutral atoms ions. Despite its significance, the predator-prey relationship between ions and neutral atoms theorized to drive this mode has lacked concrete diagnostic evi- dence. The FastOES diagnostic is employed to simultaneously measure characteristics of the neutral and ion populations through their respective emissions. The observed phase difference between Xe I and Xe II emissions is consistent with the expected phase difference between neutral and ion populations according to the predator-prey model. The FastOES diagnostic is also used to measure the time-resolved electron temperature, revealing signif- icant oscillations and a consistent out-of-phase relationship between the discharge current and electron temperature.