Development of a Two-photon Absorption Laser Induced Fluorescence Diagnostic for Proto-MPEX*

Two-photon laser induced fluorescence (TALIF) provides a non-perturbative method to directly measure mean bulk flow, temperature, and absolute densities of neutral deuterium in fusion-like plasmas. Implementation of TALIF on the Prototype Material Plasma Exposure eXperiment (Proto-MPEX) produces several technical challenges to overcome. First, probing neutral deuterium requires high intensity, VUV light creating significant difficulties for transmitting laser light through a beam path  and standard vacuum windows. Second, limited optical access complicates designs for TALIF injection and collection optics. Lastly, absolute density measurements require calibration, usually using krypton or xenon gas. We present designs for beamline path, confocal injection optics, and shot-to-shot calibration to address each challenge. TALIF will be used to measure neutral deuterium densities, temperatures, and flows in the helicon source region and ultimately in front of a target exposed to fusion-like conditions.