The transport of emitted methane molecules has been analyzed with the 3D Mo
nte Carlo code ERO. A D/XB coefficient is defined and allows a conversion o
f line-of-sight intensity of the integrated molecular CD band into the meth
ane 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 c
omparison with those obtained from a OD reaction model where the transport
is included by defining particle residence times, A calculation for ASDEX-U
pgrade using a plasma background generated with the B2-Eirene code is prese
nted. (C) 1999 Elsevier Science B.V. All rights reserved.