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Observation of wall stabilization and active control of low- n magnetohydrodynamic instabilities in a tokamak

1996; American Institute of Physics; Volume: 3; Issue: 5 Linguagem: Inglês

10.1063/1.871988

1527-2419

T. Ivers, E. Eisner, A. M. Garofalo, R. Kombargi, M. E. Mauel, D. Maurer, D. Nadle, G.A. Navratil, M. K. V. Sankar, Man-Nung Su, E. Taylor, Qirong Xiao, R.R. Bartsch, W.A. Reass, G. A. Wurden,

Superconducting Materials and Applications

The High Beta Tokamak-Extended Pulse (HBT-EP) experiment [J. Fusion Energy 12, 303 (1993)] combines an internal, movable conducting wall with a high-power, modular saddle coil system to provide passive and active control of long wavelength magnetohydrodynamic (MHD) instabilities. Systematic adjustment of the radial position, b, of the conducting wall elements in relation to the surface of the plasma (minor radius a) resulted in the suppression of β-limiting disruptions for discharges in which b/a<1.2 and a positive plasma current ramp was maintained. Conducting wall stabilization of kink instabilities was observed in discharges with strong current ramps and in plasmas with β values near the Troyon stability boundary. The frequency of slowly growing modes that persisted in wall-stabilized discharges was controlled by applying oscillating m=2, n=1 resonant magnetic perturbations. A compact, single-phase saddle coil system permitted modulation of the rotation velocity of internal m/n=2/1 instabilities by a factor of 2.