Optical emission spectroscopy and collisional radiative modeling of xenon and krypton for the diagnosis of electric propulsion plasma dynamics

This research aims to expand capabilities to diagnose the electric propulsion plasma environment, such as that of Hall thrusters relevant to planetary science missions, using optical emission spectroscopy (OES). OES allows for non-perturbing measurements of plasma properties such as electron temperature and density that are essential to understanding thruster plasma dynamics. A non-invasive method such as OES is needed in high performance thruster plasma measurements since a direct probe measurement could disturb the plasma environment or damage the probe. To yield plasma measurements, OES requires an accompanying collisional radiative (CR) model of atomic processes, which needs to be validated by direct Langmuir probe measurements of similar plasma conditions amenable to direct probe insertion. A new CR model initiated at NASA's Jet Propulsion Laboratory is being developed for krypton, and an existing CR model for xenon will be further validated. Langmuir probes, including double probes, are being developed that are suitable for a new radio frequency (RF) plasma generation environment at the University of Alaska Anchorage, and design details as well as initial measurements of electron temperature and density are presented. The probe measurements are conducted at locations within an RF argon discharge column that are accessible to spectroscopic lines of sight, such that probe data can inform CR model development and can be compared to CR model outputs. Details about the RF source and plasma generation are also presented.