Inferring neutral density profiles in opaque plasmas at high magnetic field on Alcator C-Mod *

An analysis workflow for inferring neutral density profiles from Alcator C-Mod deuterium Lyman-alpha (Ly-a) measurements has been developed for comparison with edge modeling codes. Ly-a data present a unique opportunity to investigate how deuterium neutrals affect the formation of the edge pedestal. High densities made possible by high fields on C-Mod allow study of edge neutral opacity on neutral penetration, important for next-generation devices. We present inferences of neutral density and ionization source profiles spanning a region of ~6cm about the last closed flux surface (LCFS). A tomographic inversion technique is used to calculate local neutral emissivity from line-integrated Ly-a brightness measurements at the outer midplane. This is combined with measurements of electron density and temperature from the edge Thomson scattering system, as well as scanning Langmuir probes when available. The two-point model is used to identify the position of the LCFS and shift the kinetic profiles. Uncertainty quantification techniques propagate errors from measurements to inferred profiles. An extensive database of these profiles, along with kinetic and neutral emissivity profiles, enables comparisons in different confinement regimes with edge modeling codes like KN1D and SOLPS-ITER.