Modeling of three-dimensional neutral transport in tandem mirror plasmas using a Monte-Carlo code

Modeling of neutral transport in the tandem mirror plasmas has been performed based on simulation studies using a Monte-Carlo code. A three-dimensional neutral transport simulation in both the central-cell (an axisymmetric simple mirror) and anchor-cell (a non-axisymmetric minimum-B configuration) was successfully carried out using the DEGAS version 63 code. In order to realize the geometrical structure in the simulation space, a 'second wall' is introduced in the code, which enabled us to perform a more detailed simulation. The simulation results agreed well with the Hα measurements of the experiment. The effect of cold gas influx from the beamline of the neutral beam injection (NBI) system on the particle fueling is also investigated and it is found that the azimuthally uniform particle source due to the recycling on the central vacuum chamber wall prevails over the localized fueling from cold gas influx accompanying the NBI.