Critical Toroidal Rotation Profile for Resistive Wall Modes and Control of Magnetic Islands in Tokamaks
نویسنده
چکیده
Abstract A three-mode model for the resistive wall modes based on the toroidally coupled resistive wall tearing modes is developed. The linear neoclassical tearing mode response is used at the singular surfaces to enhance plasma inertia and reduce the toroidal rotation speed for stability. The dispersion relation is obtained from the determinant of a 6×6 matrix. The toroidal rotation profile for the stability of the coupled mode can be determined by coupling the dispersion relation to the toroidal momentum balance equation. It is illustrated that toroidal rotation profile is more relevant to the stability of the resistive wall modes than the toroidal rotation speed at a given radius. The appearance of the magnetic islands degrades plasma confinement. It is shown that the width of the magnetic island can be controlled by the bootstrap current density induced by the ablation of the injected pellet at the island O-point. The magnetic island can be healed if the pellet induced bootstrap current density is large enough. It is also demonstrated that tailoring plasma profiles can control the stability of the island.
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