Spectroscopic Measurements on the Lithium Tokamak eXperiment

The Lithium Tokamak eXperiment (LTX) is a spherical torus designed to investigate the very low-recycling, liquid lithium wall regime for magnetically confined plasmas. Visible spectroscopic measurements made using two filterscopes (one viewing the center-stack, one the shell edge and molybdenum limiter) give (D$_\alpha$) a qualitative idea of the particle fueling/recycling, (CIII and OII) an indication of progress in LTX wall conditioning, and (LiI) an indication of the lithium-plasma interaction. The reflectivity of the plasma-facing-components hinders accurate quantitative measurements of recycling using D$_\alpha$ emission; the negligible VUV reflectivity of lithium motivates use of Lyman-$\alpha$ emission instead. Three instruments measure Lyman-$\alpha$ emission around most of the poloidal cross-section: two arrays viewing the center stack/inboard shell and outboard shell, and a single diode viewing a molybdenum limiter. The effects of fueling and wall conditioning on Lyman-$\alpha$ emission will be discussed. Lyman-$\alpha$ measurements will be used with a neutral transport code to calculate calculate recycling and the neutral particle deposition profile.