Analysis of neutrals in helical-axis Heliotron J plasmas using the DEGAS Monte-Carlo code

)Analysis of neutral particle behavior in Heliotron J device with non-axisymmetric configuration is described based on the results of neutral transport simulation. DEGAS three-dimensional (3-D) Monte-Carlo code was applied to Heliotron J in order to investigate precisely the spatial distribution of neutral particle density in the device. A detailed three-dimensional mesh structure for the simulation has been designed in complicated helical axis plasma geometry as well as the whole volume of Heliotron J vacuum chamber. In this mesh model, a carbon target is also modeled for the simulation of the plasma-material interaction experiments. Plasma parameter dependence on neutral diffusion was investigated and a significant effect of helical geometry was clarified. Simulation results were also compared with the two-dimensional image captured with a CCD camera viewing the carbon target and the plasma-material interaction under non-axisymmetric configuration was discussed.