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Abstract

The stability of a test equilibrium relevant to the International Thermonuclear Experimental Reactor (ITER) has been studied within the framework of the neoclassical island evolution theory. The most unstable modes, with the most positive matching index, have been found by solving numerically the marginal magnetohydrodynamic stability equation in toroidal geometry to have 3/2, 2/1, and 4/3 helicities.

Quasi -linear effects resulting from the current profile flattening as the island develops are important and stabilizing. Nonetheless, large saturated islands are predicted to arize due to a combination of strong bootstrap current drive and weakly negative.

We propose to apply a Continuous Current Drive (CCD) at the unstable rational surface to locally tailor the current profile by inducing favourable current gradients on either side of the rational surface. An important reduction of the island size, which is proportional to the current drive and inversely proportional to the square of the current channel width can then be achieved. The so obtained stabilization relies on the removal of free energy in the outer region and can thus be regarded as an effect. ct.

Additional information

Authors: PLETZER A, Centre de Recherches en Physique des Plasmas Ecole Polytechnique Federale (CH);PERKINS F W, ITER-JCT, California (US)
Bibliographic Reference: Article: Stabilization of Neoclassical tearing Modes Using a Continuous Current Drive, 1998, 1-16
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