Investigation of carbon transport in the scrape-off layer of TEXTOR-94

(CH4)-C-13 was injected into 18 consecutive ohmic discharges (108 s) through a hole in a graphite block equipped with an aluminium plate. CH and CII radical emission adjacent the hole was observed by spectroscopy, while the incremental grow of the deposit was measured in situ by colorimetry, SIMS depth profiling yielded the fractions of C-13 and of the C-12 out of the background. Ratios up to C-13/C approximate to 0.42 were found although the deposition efficiency for C-13 was only about 0.2%. H and D were co-deposited up to ratios of 0.4 and 0.2, respectively, as measured by NRA and ERDA, The results can be simulated quantitatively by means of the ERO-TEXTOR code if high re-erosion is assumed for the hydrogen rich radicals CHx+. Within the interaction depth the C-13/C ratio seems to become quasi-stationary. C-13 transported to obstacles creates a ratio of C-13/C approximate to 0.27 after 108 s, (C) 2001 Elsevier Science B.V, All rights reserved