Neutral particle transport under strong hydrogen recycling condition in the GAMMA 10 central cell

In order to understand the behavior of neutral hydrogen in ICRH plasmas of the GAMMA 10 tandem mirror, we tried new simulations of neutral transport b y using the DEGAS Monte Carlo code in which the effects of hydrogen recycli ng were taken into account. This simulation has been performed by introduci ng a multiplication coefficient in DEGAS to control the amount of desorbed test particles, which enables us to simulate the neutral transport for the first time under the conditions in which the recycling coefficient exceeds unity. By using the multiplication coefficient, it was found that the axial profile of the atomic hydrogen density obtained from the simulation change d significantly. On the other hand, there is little influence on the radial profile of the simulated hydrogen density. The simulation result, taking t he axial variation of the multiplication coefficient into consideration, we ll predicted the result of the H-alpha-emission measurements. This indicate s that strong hydrogen recycling is localized near the midplane. These calc ulation results are discussed from the view point of the wall-reflux coeffi cient deduced from the DEGAS simulation. (C) 1999 Elsevier Science B.V. All rights reserved.