Aachen PK 2003 – scientific programme
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P: Plasmaphysik
P V: HV V
P V.1: Invited Talk
Tuesday, March 18, 2003, 14:45–15:15, FO1
Impurity Transport Studied by Tracer Injection — •Rainer Burhenn1, W7-AS team1, ECRH group2, and NI group1 — 1Max-Planck-Institut fuer Plasmaphysik, Sub-Institute Greifswald, EURATOM-Ass., D-17491 Greifswald, Germany — 2Institut fuer Plasmaforschung, Universitaet Stuttgart, D-70569 Stuttgart, Germany
Impurity ions, sputtered from plasma facing materials and penetrating into the plasma, can represent a severe loss channel for plasma energy by radiation, depending on the impurity species and the plasma parameters. As a consequence, the confinement time of these ions - opposite to the energy confinement time - is demanded to be short for favourable conditions and much effort was undertaken in order to establish such scenarios. In this connexion, the study of the impurity confinement became a highly important field of investigation. Stationary impurity density profiles allow only access to the ratio of convective drifts to diffusion. Deeper insight into the impurity confinement properties can only be achieved by means of transient sources such as pulsed injection of impurity ions. Various techniques (gas puff, micro-pellet or impurity pellet injection) were develloped, the laser blow-off method being one of the most widely used.. The methods were elucidated with emphasis on the laser blow-off technique and supported by transport investigations mainly performed at the stellarator Wendelstein 7-AS.