Studies Of Impurity Migration In Textor By Local Tracer Injection

Tracer experiments have been carried out by injection C-13 marked methane through test limiters exposed to the scrape-off-layer in TEXTOR. The influence of impact energy and flux on depositing C-13 species has been studied. One experiment has been performed with biased test limiter (-300 V) in order to increase energy of positively charged ions and the other one with 10 times reduced (CH4)-C-13 injection rate compared to previously used injection rate. Biasing of the test limiter increases the resulting C-13 deposition by a factor of similar to 6 - post-mortem analysis yields a C-13 deposition efficiency of similar to 1.7% compared to similar to 0.3% without biasing. Reducing the injection rate increases C-13 deposition efficiency to similar to 0.7%, which is more than two times larger compared to experiments with previously used injection rate. ERO modelling shows that enhanced re-erosion of redeposits is still necessary to reproduce measured C-13 deposition efficiencies. (C) 2013 Elsevier B. V. All rights reserved.