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

(CH4)-C-13 was injected into 18 consecutive ohmic discharges (108 s) throug h a hole in a graphite block equipped with an aluminium plate. CH and CII r adical emission adjacent the hole was observed by spectroscopy, while the i ncremental grow of the deposit was measured in situ by colorimetry, SIMS de pth profiling yielded the fractions of C-13 and of the C-12 out of the back ground. Ratios up to C-13/C approximate to 0.42 were found although the dep osition 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 afte r 108 s, (C) 2001 Elsevier Science B.V, All rights reserved.