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TCV has the highest power (3MW in X2 and 1.5MW in X3, 2.0s) and most ITER-relevant ECH system in the world today, owing to its real-time poloidal and toroidal steerable mirrors. This paper summarises recent TCV discharges using ECH. In non-inductive discharges, the co-ECCD deposition was placed off-axis creating a large bootstrap fraction and a flat or slightly reversed shear current profile, even though the EC driven current is peaked or only slightly hollow due to radial diffusion. After reaching equilibrium, on-axis counter-ECCD was injected enhancing the reverse shear by increasing the bootstrap fraction (80%) and rapidly increasing the confinement time (T(e)), a factor of 1.6 over ITER L-mode scaling. The ITB is generated in stationary conditions and is sustained for 10 times the current redistribution time. Experimental results have shown that the improved T(e) is directly related to the degree of reverse shear in the centre. In particular, the electron temperature and pressure profiles are controlled by the amount od counter-ECCD on-axis, and in particular the gradients can be tuned to be marginally MHD stable. No power threshold for the ITB formation is observed. In other discharges the sawteeth are destabilised (stabilised) when heating just inside (outside) the q=1 surface. Control of the sawteeth allows the avoidance of NTMs that are otherwise seeded by the sawtooth instability. A transport code linked to a sawtooth model reproduces the variation in sawtooth period with the EC deposition location. Finally, preliminary results with the X3 top-launch have shown 70% single-pass absorption with 0.9MW and densities up to 0.5 10{20)m{-3} in good agreement with the absorption calculated by a linear ray tracing code.

Additional information

Authors: SUSHKOV A, Russian Research Centre "Kurchatov Institute", Moscow (RU);HENDERSON M A ET AL, Centre de Recherches en Physique des Plasmas, Association EURATOM-Confédération Suisse, Ecole Polytechnique Fédérale de Lausanne (CH);ANGIONI C, Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching (DE);FURNO I, Los Alamos National Laboratory, Los Alamos (US);PEYSSON Y, Association Euratom-CEA sur la Fusion, DFRC, CEA Cadarache, Saint-Paul-lez-Durance (FR);RAJU D, Institute for Plasma Research, Bhat, Gandhinagar, Gujerat (IN);REIMERDES H, General Atomics, San Diego (US)
Bibliographic Reference: An oral report given at: 44th Anual Meeting of the Division of Plasma Physics (APS) Organised by: American Physical Society Held at: Orlando, Florida (USA), November 11-15 2002
Availability: Available free of charge from: École Polytechnique Fédérale de Lausanne (EPFL), Ecublens, CH-1015 Lausanne Fax +41-21-6934747
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