MHD limits in non-inductive tokamak plasmas: simulations and comparison to experiments on Tore Supra

P. Maget, H. Lütjens, G. Huysmans, M. Ottaviani, X. Garbet, Ph. Moreau, J.L. Ségui

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

Abstract

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 [1]. 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 [2], a sawtooth-like behaviour of the (2,1) Double-Tearing Mode as first seen in TFTR [3], or a large amplitude (2,1) tearing mode that severely degrades the energy confinement, as reported in Tore Supra [4], JET [5] or DIII-D [6]. Situations where qmin≈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 derived in [7] could explain linear stability, but such effect vanishes in presence of heat transport [8]. Electron diamagnetic rotation effect is investigated as a possible mechanism for n = 1 mode stabilization.
Original languageEnglish
Title of host publicationTheory of fusion plasmas : joint Varenna-Lausanne international workshop, Varenna, Italy, 25-29 August 2008
EditorsX. Garbet
Place of PublicationMelville, NY
PublisherAmerican Institute of Physics
Pages153-164
Number of pages12
ISBN (Print)978-0-7354-0600-1
DOIs
Publication statusPublished - 1 Nov 2008
Externally publishedYes

Publication series

NameAIP Conference Proceedings
Volume1069
ISSN (Print)0094-243X

Keywords

  • Tokamaks spherical tokamaks
  • Magnetohydrodynamics
  • Nonlinear and dynamical symmetries

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