Transport of hydrocarbon molecules in the edge plasma of fusion experiments

The transport of emitted methane molecules has been analyzed with the 3D Monte Carlo code ERO. A D/XB coefficient is defined and allows a conversion of line-of-sight intensity of the integrated molecular CD band into the methane influx density by multiplication. This coefficient has been calculated for a wide range of plasma parameters (electron temperature and density). A strong dependence on the sticking probability of the different hydrocarbon molecules to the surface has been observed. The results are discussed in comparison with those obtained from a OD reaction model where the transport is included by defining particle residence times, A calculation for ASDEX-Upgrade using a plasma background generated with the B2-Eirene code is presented. (C) 1999 Elsevier Science B.V. All rights reserved.