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It has been predicted that radial electric fields E(r) should lead to convective effects inside the plasma. In order to distinguish between the E(r)-induced convective effect on positively charged particles from that of a general reduction of diffusion taking place during H-modes, experiments have been performed on edge-polarised TEXTOR discharges with lithium fluoride and nickel impurities injected by laser blow-off into ohmically heated deuterium discharges. Electric fields V(E) ranging between -400 V and 700 V were applied between the limiter and the tip of the polarising electrode located 4 cm inside the plasma. With Ni injection, an increase of the impurity decay time was observed with negative edge bias as well as a decrease with the opposite polarity, supporting the conclusion that the observed effect is due to modifications of the transport inside the main plasma even in the absence of the H-mode. During the H-mode, whether steadily established when V(E) is above threshold or marginally induced by the injected impurities for V(E) just below threshold, an additional independent effect appears to be present enhancing the impurity confinement.

Additional information

Authors: GIANNELLA R ET AL., JET Joint Undertaking, Abingdon, Oxon. (GB);VAN OOST G ET AL., Ecole Royale Militaire, Bruxelles (BE);BOEDO J A ET AL., Forschungszentrum Jülich GmbH (KFA) (DE);HAWKES N ET AL., AEA Fusion, Culham Laboratory, Abingdon, Oxon. (GB);KOCSIS G, Hungarian Academy of Science, Central Research Institute for Physics, Budapest (HU)
Bibliographic Reference: Article: Proceedings of the 20th European Conference on Controlled Fusion and Plasma Physics, Vol. I (1993) pp. 47-50
Record Number: 199311160 / Last updated on: 1994-11-29
Original language: en
Available languages: en