Thomson Scattering Measurements of Electron Temperature and Density on the Lithium Tokamak Experiment (LTX)

The Lithium Tokamak eXperiment (LTX) is a spherical tokamak in which the plasma is almost entirely surrounded by a lithium-coated plasma-facing shell (5 m$^{2}$ area) conformal to the last closed magnetic flux surface. Based on previous experimental results and simulations, it is expected that the low-recycling liquid lithium surfaces will result in higher temperatures at the plasma edge, flatter overall temperature profiles, centrally-peaked density profiles, and an increased confinement time. To test these predictions, the electron temperature and density profiles in LTX are measured by a multi-point Thomson scattering system (TVTS). The TVTS system employs a ruby laser (15 J, 30 ns pulse width) with a spectrometer/ICCD detector. Here, the performance of the TVTS system is discussed. Initially, Thomson scattering measurements will be performed at several points between minor radius r=0 to r=24 cm (outboard). Later, an edge view Thomson scattering system will be implemented to look at the region a few centimeters within the last closed flux surface.