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Impurity control is a key issue for the Next Step tokamak: only a low level of impurity contamination is allowed in the plasma core, whereas a highly radiating edge layer is needed to spread the power uniformly over a large wall area. Therefore, an active impurity control strategy is required. In Tore Supra, an ergodic divertor has been implemented to shield the plasma core from the impurity influx. This effect is based on the creation of a new connection to the wall, and on the enhancement of both particle and heat transport in the plasma edge. The ergodic divertor decontamination effect was analysed with impurity injection experiments. Ionisation lengths, wall effects (including conditioning), and edge confinement were found to be the key features governing the impurity screening. This effect enables a highly radiative edge layer to be obtained by an impurity injection technique, with low plasma bulk contamination.

Additional information

Authors: MONIER-GARBET P ET AL., CEA, Département de Recherches sur la Fusion Contrôlée, CEN Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Paper presented: 14th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Würzburg (DE), September 30 - October 7, 1992
Availability: Available from (1) as Paper EN 37032 ORA
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