Critical temperature gradient length signatures in heat wave propagation across internal transport barriers in the Joint European Torus
- Istituto di Fisica del Plasma 'P. Caldirola', Associazione Euratom-ENEA-CNR, Via Cozzi 53, 20125 Milano (Italy)
- LPP-ERM/KMS, Association Euratom-Belgian State, TEC, B-1000 Brussels (Belgium)
- Culham Science Centre, EURATOM/UKAEA Fusion Association, Abingdon OX14 3DB (United Kingdom)
- Association Euratom-CEA, CEA-DSM-DRFC Cadarache, 13108, St. Paul-lez-Durance Cedex (France)
- Association Euratom-Confederation Suisse, CRPP, EPFL, CH 1015, Lausanne (Switzerland)
- Max-Planck Insitut fur Plasmaphysik, Euratom Association, 85748 Garching (Germany)
- Helsinki University of Technology, Association Euratom-TEKES, P.O. Box 2200 (Finland)
- Association Euratom-TEKES, VTT, P.O. Box 1000, FIN-02044 VTT (Finland)
New results on electron heat wave propagation using ion cyclotron resonance heating power modulation in the Joint European Torus (JET) [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasmas characterized by internal transport barriers (ITBs) are presented. The heat wave generated outside the ITB, and traveling across it, always experiences a strong damping in the ITB layer, demonstrating a low level of transport and loss of stiffness. In some cases, however, the heat wave is strongly inflated in the region just outside the ITB, showing features of convective-like behavior. In other cases, a second maximum in the perturbation amplitude is generated close to the ITB foot. Such peculiar types of behavior can be explained on the basis of the existence of a critical temperature gradient length for the onset of turbulent transport. Convective-like features appear close to the threshold (i.e., just outside the ITB foot) when the value of the threshold is sufficiently high, with a good match with the theoretical predictions for the trapped electron mode threshold. The appearance of a second maximum is due to the oscillation of the temperature profile across the threshold in the case of a weak ITB. Simulations with an empirical critical gradient length model and with the theory based GLF23 [R. E. Waltz et al., Phys. Plasmas, 4, 2482 (1997)] model are presented. The difference with respect to previous results of cold pulse propagation across JET ITBs is also discussed.
- OSTI ID:
- 21069826
- Journal Information:
- Physics of Plasmas, Vol. 14, Issue 9; Other Information: DOI: 10.1063/1.2772618; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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