An overview of the atomic data and spectroscopy of low charge states of W for use in Plasma Facing Component studies

Tungsten (W) spectroscopy is important for diagnosis of gross and net erosion from plasma-facing components using the SXB method. Recent years have seen a significant improvement in the quality of the atomic data for W, including electron-impact excitation data for neutral W[1], W+[2], and W2+. An overview is given of the new atomic data, along with spectral comparisons of W I, W II, and W III emission lines from the Auburn CTH experiment and the DIII-D tokamak, using a high-resolution high-throughput UV spectrometer. Of particular value are wavelength windows showing emission from multiple charge states, making UV observations critical. The new data is shown to be a large improvement in predicting line intensities compared with those from previously available atomic datasets, with the behavior of metastable states also being important. The largest atomic data uncertainty in the SXBs is the excited state ionization data, leading to a set of large-scale R-matrix with pseudostates calculations for W2+ reported here. This will be followed by calculations for W+ and neutral W.