Confinement and profile changes induced by the presence of positive or negative radial electric fields in the edge of the TEXTOR tokamak
Edge radial electric fields were induced in the edge of the TEXTOR tokamak by means of a polarisation electrode in order to study their influence on the plasma edge profiles and its confinement. The studies included the generation of H-mode behaviour with either positive or negative polarity. Particle confinement (tau(p)) of deuterium and of impurity ions as well as energy confinement (tau(E)) were investigated. For positive fields which remained below the threshold for the L-H transition, an interesting regime of reduced particle confinement without noticeable energy confinement loss was found. A strong asymmetry in the edge density profiles with respect to the electric field sign was observed at these low polarisation voltages. Above the threshold, H-mode behaviour with increased energy confinement, and especially particle confinement, could be produced with either polarity of the applied electric field. It was however found that, whereas the energy confinement in positive H-modes was at least as good as that in negative ones, the ratio tau(p)/tau(E) was about three times lower in the former case.
Bibliographic Reference: Article: Nuclear Fusion, Vol. 32 (1992) No. 5, pp. 837-853
Record Number: 199211070 / Last updated on: 1994-11-29
Original language: en
Available languages: en