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Wall Stabilization of High Beta Tokamak Discharges in DIII-D

1995; American Physical Society; Volume: 74; Issue: 13 Linguagem: Inglês

10.1103/physrevlett.74.2483

1092-0145

E. J. Strait, T. S. Taylor, A. D. Turnbull, J. R. Ferron, L. L. Lao, B. W. Rice, O. Sauter, Scott J. Thompson, D. Wróblewski,

Superconducting Materials and Applications

DIII-D discharges with values of beta (the ratio of plasma pressure to magnetic pressure) up to 12.5% demonstrate that a resistive wall can stabilize low- $n$ magnetohydrodynamic (MHD) modes. In discharges with broad current profiles, beta exceeds the ideal MHD stability limit by at least a factor of 1.3 assuming no wall, but remains below the limit calculated under the assumptions that the vacuum vessel is a perfectly conducting wall. Plasma rotation is essential to stabilization, and instabilities resembling the predicted ``resistive wall mode'' appear only when the rotation velocity approaches zero.