Two-photon Absorption Laser Induced Fluorescence in a Hot Deuterium Toroidal Plasma: Measurements of Absolute Density, Temperature, and Flow Speed of Deuterium Neutrals

Two-photon Absorption Laser Induced Fluorescence (TALIF) has been demonstrated at WVU for measurements of krypton, hydrogen, deuterium, and xenon neutral particle distribution functions in helicon plasmas. We report now on deuterium measurements in a hot, ion temperatures up to 20 eV, spheromak. We have measured densities lower than 10$^{16}$ particles per meter cubed and neutral temperatures higher than 2 eV. The flow speeds suggest significant momentum coupling between the ions and neutral gas. The absolute density calibration is obtained by comparing a TALIF measurement of Kr gas of a known pressure with the TALIF signal from D and employing the known absorption cross section ratio for Kr and D along with other calibration factors.