New \textit{R-}matrix calculations of neutral W electron-impact excitation and ionization for PFC erosion diagnostics*

The erosion rate of tungsten PFCs can be diagnosed spectroscopically using spectral line intensity measurements combined with a set of `ionizations per photon’ coefficients (also called S/XB ratios). The accuracy of this diagnostic technique depends critically upon the quality of the atomic data comprising the S/XB ratio. This project aims to improve the accuracy of W excitation and ionization atomic data using non-perturbative methods. Synthetic spectra generated from existing perturbative W data are used to guide the size of the new $\textit{R}$-matrix calculations. The new data is used to generate a synthetic spectrum, which is compared with measured DIII-D ultraviolet spectra to determine the optimal lines for diagnosing W erosion. The new ionization rate coefficients are compared with literature values. The new S/XB ratio for the 400.9 nm line is compared with measured values and the density, temperature and metastable dependence of the S/XB ratios for new UV lines are investigated.