Ballooning Instability Precursors to High b Disruptions
Authors: E. D. Fredrickson, K. M. McGuire, Z. Y. Chang, A. Janos, J. Manickam, G. Taylor, S. Mirnov, I. Semenov, D. Kislov, D. Martynov
Strongly ballooning modes have been found as precursors to high b disruptions on TFTR. The modes are typically localized to a region spanning about 60° in the toroidal direction. The toroidal localization is associated with lower frequency, global Magneto-Hydro-Dynamic (MHD) activity, typically an ideal n=1 kink mode. They have moderate to high frequency (f = 10-20 frot), implying toroidal mode numbers in the range n = 10-20. The growth rates for the modes are large, of order 104/sec.