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Abstract

Lower hybrid current drive has been demonstrated to be an efficient tool to modify the current profile in order to access to high energy confinement regimes. Counter-current drive could be an alternative scenario provided the current drive efficiency is not too small when fast electrons flow in the opposite way to the DC electric field.
By reversing the toroidal field (Bt=-3.1T) and plasma current (Ip=-1.45MA), conter current drive with lower hybrid waves has been investigated for the first time in JET. The experiments were carried out at low plasma density (n{e}=1.0 x 10{19}m{-3}, n(e)(0)= 1.6 x 10{19}m{-3}) with 2.9 MW of lower hybrid power.
The CRONOS code, which couples the diffusion equations to a 2-D equilibrium code, has been used to estimate the RF driven current. Runs indicated that loop voltage and internal inductance are best simulated with a current drive efficiency of -1.0 x 10{19} A.W{-1}.m{-2}with a peaked central LH power deposition deduced from DELPHINE. This efficiency is indeed very close to the one found for co-LHCD at similar plasma current and density. Current profile evolves from a hollow profile (with a minimum at r/a ~0 and a maximum at r/a~0.4-0.5) to a rather lat profile (up to r/a-0.3).

Additional information

Authors: BASIUK V, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);GONICHE M, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);ARTAUD J F, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);EKEDAHL A, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);IMBEAUX F, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);MAZON D, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);PEYSSON Y, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);MAILLOUX J, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB)
Bibliographic Reference: An oral paper given at: 12th International Congress on Plasma Physics Organised by:CEA Research Centres, France Held at: Acropolis conference center, Nice (FR)
Availability: Available from Association EURATOM-CEA, Departement de Recherches sur la Fusion Controlee, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: dirdrfc@drfc.cad.cea.fr
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