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Abstract

A simple analytic fluid model based on particle and momentum conservation describes the response of the scrape-off layer to an applied radial electric field. The model explains why the variation of plenum pressure during limiter biasing in TEXTOR shows the opposite behaviour as divertor biasing in Tokamak de Varennes: the mechanical baffles that define the throats of the pump limiter are aligned along the magnetic field, thus preventing collection of the induced perpendicular flux when the drift is directed towards the scoop. Rather, the optimal pumping is expected when the drift is directed away from the scoop due to the increase of the parallel flux needed to satisfy the Bohm-Chodura criterion. Qualitative agreement is obtained with measurements of the parallel flow near the limiter throat, and with measurements of the plenum pressure during negative biasing for both directions of toroidal magnetic field. The results, extrapolated to Tore Supra, predict that the actual design with throats should provide close to optimal pumping with minor modification of the natural radial electric field, but greater performance could be obtained with negative biasing if a toroidally symmetric neutraliser geometry were adopted.

Additional information

Authors: GRAVIER E ET AL, Association Euratom-CEA Cadarache, St. Paul-lez-Durance (FR);MANK G, Institut für Plasmaphysik, Forschungszentrum, Jülich GmbH, EURATOM Association, Jülich (DE);FINKEN K-H, Institut für Plasmaphysik, Forschungszentrum, Jülich GmbH, EURATOM Association, Jülich (DE);LEHNEN M, Institut für Plasmaphysik, Forschungszentrum, Jülich GmbH, EURATOM Association, Jülich (DE);BOUCHER C, INRS-Energie et matériaux, Varennes, Canada (CA);JACHMICH S, Laboratory for Plasmaphysics, Association `EURATOM - Belgian State', Brussels (BE);VAN OOST G, Department of Applied Physics, Ghent University, Gent (BE)
Bibliographic Reference: An article published in: Nuclear Fusion, 42 (June 2002), pp. 653-662
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://stacks.iop.org/0029-5515/42/653
Record Number: 200215040 / Last updated on: 2002-07-29
Category: PUBLICATION
Original language: en
Available languages: en
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