Neutral Density Profiles in the HSX Stellarator

Neutral density distribution in HSX plasma is calculated using the 3D Monte-Carlo neutral particle code, DEGAS. Calculated neutral density is then scaled with poloidal and toroidal H-alpha measurements to obtain a radial profile of averaged neutral densities in the plasma. Calculations are done for the quasi-helically symmetric and symmetry degraded configurations of HSX, for various plasma and wall conditions. The scaling factor obtained from present and previous experiments (with core electron temperature \textasciitilde 1.5keV and plasma density \textasciitilde 3x10$^{\mathrm{18}}$/m$^{\mathrm{3}})$ is used to scale neutral density profiles from simulations of the HSX upgrade, where higher plasma density (\textasciitilde 2x10$^{\mathrm{19}}$/m$^{\mathrm{3}})$ is expected. Initial results show a significant reduction (about a factor of 4) in the neutral hydrogen density for the HSX upgrade parameters.