MHD limits in non-inductive tokamak plasmas: simulations and comparison to experiments on Tore Supra
- CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France)
- Centre de Physique Theorique (Ecole Polytechnique), 91128 Palaiseau (France)
Non-inductive tokamak discharges with a flat or hollow current profile are prone to the triggering of large tearing modes when the minimum of the safety factor is just below a low order rational. This issue is of particular importance for discussing the optimal safety factor for MHD modes avoidance in Steady-State reactor plasmas. Different non-linear regimes of such magnetic configurations in Tore Supra are studied using the full MHD code XTOR. Numerical simulations show that the non-linear stage of the Double-Tearing Mode (DTM) is governed by the full reconnection model, but a single tearing mode in a low magnetic shear configuration can have a similar impact on the confinement. The different regimes observed experimentally are recovered in the simulations: a small amplitude (2,1) DTM for close resonant surfaces as seen in Tore Supra, a sawtooth-like behaviour of the (2,1) Double-Tearing Mode as first seen in TFTR, or a large amplitude (2,1) tearing mode that severely degrades the energy confinement, as reported in Tore Supra, JET or DIII-D. Situations where q{sub min}{approx_equal}1.5 with a stable n = 1 mode, as seen in Tore Supra longest discharges, seem to put specific constraints on the MHD model that is used. Indeed, curvature stabilisation without transport terms as could explain linear stability, but such effect vanishes in presence of heat transport. Electron diamagnetic rotation effect is investigated as a possible mechanism for n = 1 mode stabilization.
- OSTI ID:
- 21251731
- Journal Information:
- AIP Conference Proceedings, Vol. 1069, Issue 1; Conference: Joint Varenna-Lausanne international workshop on theory of fusion plasmas, Varenna (Italy), 25-29 Aug 2008; Other Information: DOI: 10.1063/1.3033698; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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