Christopher V Young, Mark A Cappelli
2016 Zenodo  
Hall thrusters are a mature form of electric propulsion for spacecraft well suited for north-south station keeping, orbit transfer maneuvers, and eventually deep space travel. Despite decades of development, producing propulsion systems with high operating efficiency and specific impulse, key aspects of the physics governing these complex devices remain poorly understood and fundamental experimental and computational studies persist. The collection of plasma oscillations, instabilities, and
more » ... ulent fluctuations present in Hall thrusters make for rich electron and ion dynamic behavior that is the subject of this investigation. Laser diagnostics of plasmas avoid perturbing the discharge (unlike physical probes), and recent advances in diode laser technology allow for very narrow spectral lineshapes to be easily interrogated with continuous-wave diode lasers. This work concerns the development and implementation of laser-induced fluorescence diagnostics for probing time-resolved dynamics in systems with a quasi- periodic forced or naturally occurring oscillation. Relaxing the requirement of a fixed frequency spectrum over time distinguishes the sample-hold and fast switching LIF methods studied here from others currently in use. The methods are validated against a collisional-radiative model of a 60 Hz xenon test discharge, successfully predicting the time evolution of excited xenon state populations. A statistical consideration of the influence of a drifting frequency and amplitude spectrum in the time-resolved methods is presented. The sample-hold method is then applied to studying xenon neutral and ion dynamics and trans- port in two Hall thruster discharges: a laboratory model in the Stanford Plasma Physics Laboratory similar to the SPT-100 class of devices, and a commercial Busek Co. BHT-600 Hall thruster at the Air Force Research Laboratory at Edwards Air Force Base, California. Parallelizing the data acquisition greatly increases data collection efficiency, allowing for full time series of LIF traces with 2 [...]
doi:10.5281/zenodo.3831450 fatcat:s5odd262ungjhastfo2ljxtlze