The neutral transport analysis based on visible light measurement of recycling and 3-dimensional simulation in GAMMA 10

Neutral transport related to recycling phenomena on two limiters installed in the central-cell was studied in the GAMMA 10 tandem mirror plasmas. Dependence of iris limiter is investigated in terms of plasma diamagnetism and Hα-line intensity. It was found that a plasma diamagnetic signal was improved and Hα-line intensity near the iris limiter increased if the diameter of the iris limiter shrank to 340 mm. Fully 3-dimensional Monte-Carlo simulation (DEGAS) was executed with the recycling source on the limiters. The neutral sources on the limiters were consistently given so as to satisfy 2-dimensional (2-d) image obtained by a high-speed camera. The determined Hα-line intensity from DEGAS well explained the experimental result. The simulation result, in the 340 mm case, predicted the reduction in the peak value of Hα-line intensity on the central limiter and the enhancement on the iris limiter. It suggests that the reduction of the recycling on the central limiter makes it possible to lead the better plasma performance. (author)