Single and Multi-photon Laser Induced Fluorescence for Electric Thruster and Fusion Applications

Single and Multi-photon Laser Induced Fluorescence for Electric Thruster and Fusion Applications Thomas Edward Steinberger Laser-based diagnostics are increasingly sought after to investigate a variety of plasmas due to their non-perturbative capabilities. Specifically, laser induced fluorescence (LIF) provides a highly localized and precise spectroscopic technique to measure absolute density, temperature, and bulk flow. In this work, LIF and two-photon absorption laser induced fluorescence (TALIF) are used to investigate electric propulsion and fusion-relevant plasmas, respectively. Ion velocity distribution functions (IVDF) of singly ionized atomic iodine (I II) are measured for the first time and lineshape characteristics are presented for the diagnosis of Hall thrusters with iodine as a propellant. A non-perturbative technique of determining external magnetic field from Zeeman split iodine spectra is also discussed and results are shown. Fusion-relevant plasmas are investigated in the Prototype Material Plasma Exposure eXperiment (Proto-MPEX) using TALIF. Ground state neutral deuterium velocity distribution functions are measured during Proto-MPEX operation. Absolute neutral density, neutral temperature, and neutral bulk flow are determined. Absolute neutral deuterium densities are calculated by calibrating measured deuterium velocity distributions with xenon and krypton. Calibrated density values from the two gases are compared. This work presents, for the first time, deuterium absolute densities calibrated using xenon, first proposed by Elliot et al. Temporal evolution of deuterium signal is shown over the entirety of a Proto-MPEX plasma pulse. Neutral density, temperature, and bulk flow dependence on radio frequency (rf) power and radial location is presented. Lastly, a novel three photon laser induced fluorescence (3pLIF) scheme is shown for krypton