Experimental validation of the SOLPS-ITER neutral model with experimental Lyman-alpha and neutral profiles on Alcator C-Mod

Accurate modeling of neutral density and ionization profiles in future tokamaks is crucial for both fueling and profile shape predictions. We validate the ability of SOLPS-ITER, a 2D fluid plasma/kinetic Monte Carlo neutral code, to accurately model upstream neutral density profiles of an L-mode, I-mode, and H-mode discharge on Alcator C-Mod. By first matching outer midplane measurements of ne and Te through iterative tuning of the perpendicular transport coefficient profiles, it is shown that SOLPS can reproduce edge profiles of the neutral D density as inferred from Lyman-alpha measurements to within uncertainties. To further validate the SOLPS neutral model, a synthetic diagnostic is implemented in SOLPS to emulate the viewing chords of the Lyman-alpha array. Simulated Lyman-alpha emissivity profiles reveal a consistent match with experiment, mostly within uncertainties. However, modeled line-integrated brightness profiles are systematically lower than experiment by a factor of ~2, implying underestimated contributions from atomic interactions. It is demonstrated that the quality of match between model and experiment degrades significantly outside of the plasma computational domain, motivating the adoption of full-vessel plasma simulations in the future.