An update on atomic data for the low charge states of W for use in simulation codes and erosion/redeposition diagnostics*

Spectroscopic techniques to measure gross and net erosion for tungsten plasma facing components require accurate atomic data. A brief review is given of the available atomic data for neutral W. Spectral comparisons of electron temperatures diagnosed from W I line ratios in the Auburn Compact Toroidal Hybrid (CTH) experiment agree favorably with Langmuir probe measurements. In support of tungsten redeposition experiments and model validation activities at DIII-D, a new R-matrix calculation for electron impact excitation of W⁺ has been completed and good agreement is also found with spectral observations from the Auburn CTH experiment. A significant number of W II lines are identified at ultra-violet wavelengths that could be useful for redeposition studies. The role of metastable levels in W⁺ is also discussed and plasma conditions are identified where their populations must be modelled time-dependently.