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Abstract

We present the results of experiments in JET to study the effect of plasma shape on high density ELMy H-modes, with geometry of the magnetic boundary similar to that envisaged for the standard Q = 10 operation in ITER. The experiments described are single lower null plasmas, with standard q profile, neutral beam heating and gas fuelling, with average plasma triangularity delta calculated at the separatrix ~0.45-0.5 and elongation kappa ~1.75. In agreement with the previous results obtained in JET and other divertor Tokamaks, the thermal energy confinement time and the maximum density achievable in steady state for a given confinement enhancement factor increase with delta. The new experiments have confirmed and extended the earlier results, achieving a maximum line average density n(e)~1.1n(GR) for H(98)~0.96. In this plasma configuration, at 2.5 MA/2.7 T (q95~2.8), a line average density ~95% (nGR) with H(98) = 1 and beta(N)~2 are obtained, with plasma thermal stored energy content Wt(h) being approximately constant with increasing density, as long as the discharge maintains Type I ELMs, up to n(ped~nGR) (and n(e)~1.1n(GR).

Finally, we present the first results of experiments by studying in more detail the effects of the plasma boundary geometry, in particular by investigating separately the effect of the upper and lower triangularity, at high average delta. We show that the changes to the lower delta (or of the radial position of the x-point) affect the pedestal parameters, the size of ELM energy losses as well as the global energy confinement of the plasma.

Additional information

Authors: SAIBENE G ET AL, EFDA Close Support Unit, Max-Planck-Institut fur Plasmaphysik, Garching (DE);LOMAS P J ET AL, Association Euratom/UKAEA, Culham Science Centre, Abingdon (GB);BECOULET M, Association Euratom/CEA, Cadarache, St Paul-lez-Durance (FR);HUYSMANS G T A, Association Euratom/CEA, Cadarache, St Paul-lez-Durance (FR);KOSLOWSKI H R, Forschungszentrum Jülich GmbH, Institut für Plasmaphysik, EURATOM Association, Trilateral Euregio Cluster, Jülich (DE);BUDNY R, PPPL, Princeton University, Princeton, NJ (US);CONWAY G D, Association Euratom/IPP, Max-Planck-Institut fur Plasmaphysik, Garching (DE);STOBER J, Association Euratom/IPP, Max-Planck-Institut fur Plasmaphysik, Garching (DE);SUTTROP W, Association Euratom/IPP, Max-Planck-Institut fur Plasmaphysik, Garching (DE);KALLENBACH A, Association Euratom/IPP, Max-Planck-Institut fur Plasmaphysik, Garching (DE);VON HELLERMAN M, FOM/Euraton Instituut v Plasmaphysica `Rijnhuizen', Nieuwegein, Trilateral Euregio Cluster (NL);BEURSKENS M, FOM/Euraton Instituut v Plasmaphysica `Rijnhuizen', Nieuwegein, Trilateral Euregio Cluster (NL)
Bibliographic Reference: An article published in: Plasma Physics and Controlled Fusion, 44 (September 2002), 1769-1799
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://stacks.iop.org/0741-3335/44/1769
Record Number: 200215616 / Last updated on: 2002-12-02
Category: PUBLICATION
Original language: en
Available languages: en
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