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Abstract

We report here the observation of MHD modes identified as electron fishbones in Tore Supra discharges using Lower Hybrid (LH) waves for generating most of the plasma current. Fishbone modes are marginally stable ideal modes, which are destabilised by trapped suprathermal particle, via wave-particle resonance at the toroidal precession frequency. Ion fishbone modes are driven by deeply trapped ions, and they destabilise the internal kink, as well as the double-kink modes. This latter form of ion fishbone has been observed in JET Optimised Shear scenario. The mechanism for electron fishbone is similar, except that the ideal mode is destabilized by barely trapped electrons. Up to now, electron fishbone modes have only been observed associated to the internal (q = 1) mode, in discharges heated at the Electron Cyclotron frequency, or with LH waves. But it is natural that, in reversed magnetic shear plasmas with a suprathermal electron population, electron fishbone can exist in association with the double-kink mode. This is what we observe in Tore Supra for the first time, where the electron fishbone mode is observed in association with the double-kink mode on q = 2 and q = 3=2. The Tore Supra tokamak is equipped with two LH antennas capable of delivering about 3 MW for long duration (best present result is 3 MW for 370 s). Electron fishbone modes are observed in fully non-inductive discharges using LH, but also in other LH discharges with nonzero loop voltage, some of them having in addition a fast ion population driven by Ion Cyclotron Resonance Heating (ICRH) system.

Additional information

Authors: MAGET P et al, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: An oral paper given at: 32nd EPS Conference on Controlled Fusion and Plasma Physics Organised by: Asociación EURATOM-CIEMAT para Fusión Held at: Congress Palace of Tarragona, Tarragona (ES)
Availability: Available from Association EURATOM-CEA, Departement de Recherches sur la Fusion Controlee, CEA Cadarache, F-13108 St Paul-Lez-Durance, FranceL%Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: dirdrfc@drfc.cad.cea.fr
Record Number: 200518285 / Last updated on: 2005-07-26
Category: PUBLICATION
Original language: en
Available languages: en
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