Ballooning instability precursors to high β disruptions on the Tokamak Fusion Test Reactor

Toroidally localized ballooning modes have been found as precursors to high β disruptions in many regimes on the Tokamak Fusion Test Reactor (TFTR) [D. Meade et al., Proceedings of the International Conference on Plasma Physics and Controlled Nuclear Fusion, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. I, pp. 9–24]. Lower frequency, global magnetohydrodynamic (MHD) activity, typically an ideal n=1 kink mode, causes the toroidal localization. Larger-amplitude n=1 modes result in stronger toroidal localization of the ballooning modes. The modes are typically localized to a region spanning about 90°–120° in the toroidal direction.