Recycling studies based on two-dimensional visible light measurements and Monte-Carlo simulation in mirror and helical systems

Analysis of neutral particle behavior in the GAMMA 10 tandem mirror with open magnetic field and the Heliotron J device with non-axisymmetric plasma confining system is described based on the results of Monte-Carlo neutral transport simulation. Three-dimensional (3-D) Monte-Carlo code DEGAS was applied to both devices in order to investigate precisely the spatial distribution of neutral particle density. In GAMMA 10, a detailed structure of inner components of the central-cell is modeled in the simulation space. In Heliotron J, a carbon limiter inserted into the plasma for investigation of plasma-material interactions is also modeled in addition to the helically twisted vacuum vessel and plasma. In both devices, 2-D images of light-emission from the plasma captured with CCD cameras near the limiters are compared with the simulation results and a good agreement between experiment and simulation is recognized. Comparison of the decay length in the emissivity of Hα/Dα line-emission also showed that neutral transport in SOL region plays a significant influence on the emission profile.