Neutral transport analysis in a non-axisymmetric plasma confining system based on a Monte-Carlo simulation

Transport of neutral particles in a non-axisymmetric plasma device is described based on a Monte-Carlo simulation and of D alpha line-emission measurements. DEGAS three-dimensional (3-D) Monte-Carlo code for neutral transport simulation has been applied to a helical-axis heliotron device, Heliotron J. In a whole area of Heliotron J vacuum vessel, a detailed 3-D mesh structure for the simulation was constructed especially for the precise investigation of particle transport in the toroidal direction. In this mesh model, a carbon target is also modeled in the simulation space, and the simulation has been carried out for the target insertion experiments in Heliotron J. Simulation results were compared with the results obtained from two-dimensional image captured with a CCD camera viewing the top surface of the carbon target. The compared results indicated that the particle source caused by the carbon target is thought to be much more localized than expected one from the D alpha image around the target. Particle transport to the toroidal direction was also discussed based on the 3-D simulation. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.