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New experimental evidence of the correlation between edge sheared E x B flow and reduction of turbulence has been measured in the CASTOR tokamak (R = 0.4m, alpha = 0.085m, B(T) = 1 T). A biasing electrode is placed at the separatrix in a configuration which has demonstrated strongly sheared electric fields and consequent improvement of the global particle confinement. A set of moveable electrostatic probes (rake, Langmuir, Gundestrup and rotating Mach) provide redundant, simultaneous measurements of poloidal flow, toroidal flow, electron temperature, density and radial electric field with high temporal resolution and at the same poloidal location. The measurements from the rake, Gundestrup and rotating Mach probes give three independent radial profiles of E x B shear in ohmic and biased modes. Good agreement is obtained both for the profile shape and its absolute magnitude. In addition we compare the measured E x B ion mass flow with the phase velocity of fluctuations moving poloidally across the Gundestrup collectors. The maximum detectable phase velocity turns out to be rather modest compared to the measured bulk poloidal flow speed.

This paper was presented at the 4th Europhysics Workshop "Role of electric fields in plasma confinement and exhaust", Funchal, Madeira, Portugal, June 24-25, 2001.

Additional information

Authors: GUNN J, Département de Recherches sur la Fusion Contrôlée, Association EURATOM-CEA Cadarache, Saint Paul lez Durance (FR);STÔCKEL J ET AL, Institute of Plasma Physics, Association EURATOM - IPP.CR, Praha (CZ);VAN OOST G, Department of Applied Physics, Ghent University, Gent (BE)
Bibliographic Reference: An article published in: Czechoslovak Journal of Physics, Vol. 51, No.10 (2001), pp.1001-1010
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Record Number: 200315728 / Last updated on: 2003-01-10
Original language: en
Available languages: en