An overview on atomic data for low charge states of tungsten and the role of excited state ionization on S/XBs

Tungsten spectroscopy involving low charge states is important for gross and net erosion diagnostics of Plasma Facing Components. A summary is given of recent work on excitation datasets for neutral W[1], W+[2], and W2+[3], along with comparisons with DIII-D spectra. The main atomic data uncertainty remaining is on the excited state ionization data in these charge states. New R-matrix with Pseudostates (RMPS) results on the ionization of W2+ are shown, with good agreement between crossed-beam measurements being found. The new data includes ionization from excited states, metastable resolution of the final state, and infinite energy points. Collisional-Radiative (CR) modeling using the new ionization data and the recently calculated excitation data [3] shows that excited state ionization contributes significantly to the effective ionization from W2+ at tokamak divertor conditions, having a significant effects on both SCD for transport modeling and S/XBs for erosion studies. We present a set of UV lines for the first three charge states that are most useful for spectroscopic studies.



[1] R. Smyth et al., Phys. Rev. A, 97, 052705 (2018)

[2] N. Dunleavy et al., J. Phys. B, 55, 175002 (2022)

[3] M. McCann et al., J. Phys. B, 57, 235202 (2024)