Spectroscopic Investigation of Tungsten Erosion**

Erosion of tungsten at the plasma boundary is spectroscopically diagnosed using improved predictions for atomic coefficients representing the ionizations per photon (S/XB). Previous W I theory estimates do not agree with the experimentally observed S/XB ratio for the 400.9 and 429.4 nm lines but new atomic data is used to calculate a ratio that is consistent with experimental observations. The Erosion of tungsten at the plasma boundary is spectroscopically diagnosed using improved predictions for atomic coefficients representing the ionizations per photon (S/XB). New W I S/XB calculations utilize R-matrix excitation data and classical exchange impact parameter (ECIP) ionization data for recently identified UV emission lines. Theoretical spectral intensities for numerous W I lines in the 200-400 nm region are compared to measurements in DIII-D and the Compact Toroidal Hybrid (CTH). Predicted spectra agree with CTH observations but differ from DIII-D observations by up to a factor of two. The contribution of metastable states to these discrepancies will be discussed.