Identification of W II spectral lines for tungsten erosion measurements using high-resolution ultraviolet spectroscopy

The potential of tungsten as a plasma facing component in future nuclear fusion devices is dependent on erosion rates when exposed to high-temperature plasmas. A tungsten-tipped Langmuir probe for simultaneously sourcing W and measuring electron temperature and density is inserted into the Compact Toroidal Hybrid (CTH) experiment for erosion studies. Tungsten emission is detected by a high-resolution spectrometer optimized for ultraviolet wavelengths used to investigate critical phenomena such as the effect of metastable states and re-deposition rates. Inserting the tungsten-tipped probe to varying depths in CTH provides a method for observing changes in the spectral intensity due to different plasma conditions. It is also necessary to acquire spectra with different probe tip materials to distinguish background spectral lines. Experiments utilizing CTH have accumulated high-resolution spectroscopic data for tungsten, molybdenum, and tantalum to identify spectroscopic lines of interest in the ultraviolet region (200-400 nm) for neutral tungsten emission. Ongoing analysis of singly ionized tungsten emission has preliminarily identified over 30 W II emission lines of potential interest for erosion measurements.