Mainz 1997 – wissenschaftliches Programm

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P: Plasmaphysik

P 13: Postersitzung I

P 13.9: Poster

Dienstag, 4. März 1997, 16:00–18:00, Foyer

Study of the causality between the radial electric field and confinement changes during edge polarisation in TEXTOR-94 — •S. Jachmich¹, A. Lyssoivan², G. Van Oost², R. Weynants², J.A. Boedo³, M. Brix¹, A. Huber¹, and B. Schweer¹ — ¹Institut für Plasmaphysik, Forschungszentrum Jülich GmbH, Association EURATOM – KfA, 52425 Jülich, Germany — ²Laboratoire de Physique des Plasmas, Association “Euratom – Belgian State”, Ecole Royale Militaire – Koninklijke Militaire School, B–1000 Brussels, Belgium — ³UCSD, Fusion Research Program, San Diego, USA

In electrode biasing experiments we induce electric fields in a controlled fashion. The electric field profiles are measured continuously during discharge phases with transitions in confinement. This enables us to investigate the relative spatial and temporal dynamics of the radial electric field E_r and of the confinement changes, mainly characterised by the local density gradient, which is inferred from Li– and He–beam diagnostics. The results pertain to positive polarisation, i.e. imposing positive E_r. As the pressure gradient contribution to E_r is always negative, the field is the consequence of strong edge plasma rotation. The plasma conditions are such that the field can be build up continuously, without jumps. It is found that E_r has to exceed a definite threshold before particle confinement improves. The confinement improvement manifests itself by the creation of a transport barrier located in the region where the field shear E_r^′ is positive.