Resistive wall mode stabilization by slow plasma rotation in DIII-D tokamak discharges with balanced neutral beam injection
- General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
Recent experiments in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] show that the resistive wall mode (RWM) can be stabilized by smaller values of plasma rotation than previously reported. Stable discharges have been observed with beta up to 1.4 times the no-wall kink stability limit and ion rotation velocity (measured from CVI emission) less than 0.3% of the Alfven speed at all integer rational surfaces, in contrast with previous DIII-D experiments that indicated critical values of 0.7%-2.5% of the local Alfven speed. Preliminary stability calculations for these discharges, using ideal magnetohydrodynamics with a drift-kinetic dissipation model, are consistent with the new experimental results. A key feature of these experiments is that slow plasma rotation was achieved by reducing the neutral beam torque. Earlier experiments with strong neutral beam torque used ''magnetic braking'' by applied magnetic perturbations to slow the rotation, and resonant effects of these perturbations may have led to a larger effective rotation threshold. In addition, the edge rotation profile may have a critical role in determining the RWM stability of these low-torque plasmas.
- OSTI ID:
- 20975040
- Journal Information:
- Physics of Plasmas, Vol. 14, Issue 5; Other Information: DOI: 10.1063/1.2472599; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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