@inproceedings{a9888581f9e14e04a350306ed31b0e00,

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

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.",

keywords = "Tokamaks spherical tokamaks, Magnetohydrodynamics, Nonlinear and dynamical symmetries",

author = "P. Maget and H. L{\"u}tjens and G. Huysmans and M. Ottaviani and X. Garbet and Ph. Moreau and J.L. S{\'e}gui",

year = "2008",

month = nov,

day = "1",

doi = "10.1063/1.3033698",

language = "English",

isbn = "978-0-7354-0600-1",

series = "AIP Conference Proceedings",

publisher = "American Institute of Physics",

pages = "153--164",

editor = "X. Garbet",

booktitle = "Theory of fusion plasmas : joint Varenna-Lausanne international workshop, Varenna, Italy, 25-29 August 2008",

address = "United States",

}