Hydrogen recycling in graphite at higher fluxes

Understanding hydrogen recycling is essential for particle control in fusio n devices with a graphite wall. At Extrap T2 three different models have be en used. A zero-dimensional (0D) recycling model reproduces the density beh avior in plasma discharges as well as in helium glow discharge. A more soph isticated one-dimensional (1D) model is used along with a simple mixing mod el to explain the results in isotopic exchange experiments. Due to high flu xes some changes in the models were needed. In the paper, the three models are discussed and the results are compared with experimental data. (C) 1999 Elsevier Science B.V. All rights reserved.