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Inhibition of contamination of the plasma core in JET by edge impurities during high power heating of deuterium plasmas in limiter configuration using fuelling has been demonstrated. By injecting deuterium gas during heating, in the presence of a much larger recycling deuterium flux, a reduction of more than factor two was achieved in the ratio of central impurity density to impurity influx at the plasma edge. The reduction in impurity density was obtained without much effect on peak electron temperature and density. Reduction of plasma contamination by gas fuelling was observed also when hot spots formed on the limiter, a condition that without simultaneous gas fuelling culminated in runaway plasma contamination. Detailed analysis of the experiments is undertaken with the purpose of identifying the processes by which plasma contamination was inhibited, employing standard limiter contamination modelling. Comparison between LIM code simulations and measurements of plasma impurity content indicate that the standard limiter plasma contamination model may not be adequate and that other processes need to be added in order to be able to describe the experiments in JET.

Additional information

Authors: GONDHALEKAR A, JET Joint Undertaking, Abingdon, Oxon. (GB);STANGEBY P C, University of Toronto, Institute for Aerospace Studies (CA);ELDER J D, University of Toronto, Institute for Aerospace Studies (CA)
Bibliographic Reference: Report: JET-P(92)89 EN (1992) 32 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
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