Defense Dissertation: Ionization Instability of the Hollow Cathode Plume
WHEN: December 13, 2019 3:00 pm
Ph.D. Candidate in Applied Physics
Committee: Alec Gallimore, Benjamin Jorns, Ryan McBride, Ioannis Mikellides, and Timothy Sarver-Verhey
In this work, we study the formation of the poorly understood process of the spot-to-plume mode transition in hollow cathodes and the associated plasma instability that generates erosive high-energy ions. We propose a novel mechanism for the onset of this wave, that has its roots in existing experimental and numerical support, whereby an ionization instability between the electrons and neutrals may be destabilized by out-of-phase temperature fluctuations and giving rise to an enhancement in the plasma particle production through ionization. Experimentally, we show that temperature oscillations in the plasma are highly-correlated the presence of plasma turbulence, which is known to drive the heating of electrons in the plasma produced by the cathode. A zero-dimensional model is derived from first principles and is investigated through experiments. The results show that the model is able to largely capture the correct trends in the wave properties with varying experimental parameters.