Atomic calculations and comparison to experiment for Si⁺ and W²⁺ erosion diagnostics

New atomic physics work is being done to build diagnostics for the erosion and re-deposition of wall materials in fusion plasmas. A new ionization calculation for W²⁺, needed to determine W re-deposition rates, is currently underway using the R-matrix with pseudostates (RMPS) method. This calculation, when combined with an existing excitation calculation for W²⁺, will be used to generate ionization/photon (S/XB) coefficients, which can be combined with spectroscopic measurements to infer time-resolved erosion and re-deposition rates. To transform the collision cross sections from the RMPS calculation into accurate derived coefficients, a new code has been developed that separates each collisional cross section into separate ionization series and extends them to high energies. The techniques used for the W²⁺ calculation have been tested by applying them to a simpler, but still useful, ion: Si⁺. Both calculations have been compared to experimental ionization cross section measurements, which justifies confidence in the derived coefficients, such as the S/XB coefficients. These calculations are being benchmarked over a range of plasma conditions from experiments completed in the DIII-D tokamak using the DiMES removable sample probe and new UV spectroscopy capabilities.