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Abstract

The TCV tokamak (R = 0.88 m, a < 0.25 m, BT < 1.54 T) is equipped with six 0.5 MW gyrotron sources operating at 82.7 GHz for second harmonic X mode ECH. By distributing the ECCD current sources over the discharge cross section, fully driven stationary plasmas with Ip = 210 kA, ne0 = 2?1019 m-3, Te0 » 4 keV, were obtained for the full discharge duration of 2 s. Highly peaked electron temperature profiles with Te0 up to 12 keV were obtained in central counter-current drive scenarios with off-axis ECH. Absorption measurements using a 118 GHz gyrotron have demonstrated the importance of supra-thermal electrons for third harmonic absorption. A coupled heat-particle transport phenomenon known as �density pumpout�, which leads to the expulsion of particles from the plasma core, has been linked to the presence of m = 1 modes, suggesting that it is due to the existence of locally trapped particles associated with the loss of axisymmetry. Highly elongated discharges have been developed with ohmic heating (k < 2.8) and off-axis ECH. The latter exhibit considerably improved vertical stability due to current profile broadening. A `gateway' for ELMy H modes has been discovered, which allows stationary ohmic ELMy H mode operation over a wide range of elongation, triangularity and density. Divertor detachment experiments suggest the existence of recombination pathways other than three body or radiative processes.

Additional information

Authors: WEISEN H ET AL, Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, Ecole Polytechnique Federale de Lausanne (CH)
Bibliographic Reference: An article published in: Nuclear Fusion, 41 (10), (2001), pp. 1459-1472
Record Number: 200214266 / Last updated on: 2002-01-21
Category: PUBLICATION
Original language: en
Available languages: en