Relationship Between Onset Thresholds, Trigger Types, and Rotation Shear for the m/n=2/1 Neoclassical Tearing Mode in a High-β Spherical Torus
Authors: S.P. Gerhardt, D.P. Brennan2, R. Buttery, R. J. La Haye, S. Sabbagh, E. Strait, M.Bell, R. Bell, E. Fredrickson, D. Gates, B. LeBlanc1, J. Menard, D. Stutman, K.Tritz, H. Yuh
Abstract:
The onset conditions for the m/n=2/1 neoclassical tearing mode (NTM) are studied in terms of neoclassical drive, triggering instabilities, and toroidal rotation or rotation shear, in the spherical torus NSTX [M. Ono, et al., Nuclear Fusion 40, 557 (2000)]. There are three typical onset conditions for these modes, given in order of increasing neoclassical drive required for mode onset: triggering by energetic particle modes, triggering by edge localized modes, and cases where the modes appear to grow without a trigger. In all cases, the required drive increases with toroidal rotation shear, implying a stabilizing effect from the shear.
__________________________________________________
Submitted to: Nuclear Fusion (October, 2008)
__________________________________________________
Download PPPL-4386 (pdf 253KB 8pp)
__________________________________________________