Onset and Saturation of a Non-resonant Internal Mode in NSTX and Implications For AT Modes in ITER
Authors: J.A. Breslau, M.S. Chance, J. Chen, G.Y. Fu, S,. Gerhardt, N. Gorelenkov, S.C. Jardin and J. Manickam
Abstract:
Motivated by experimental observations of apparently triggerless tearing modes, we have performed linear and
nonlinear MHD analysis showing that a non-resonant mode with toroidal mode number n = 1 can develop in the
National Spherical Torus eXperiment (NSTX) at moderate normalized βN when the shear is low and the central
safety factor q0 is close to but greater than one. This mode, which is related to previously identified ‘infernal’
modes, will saturate and persist, and can develop poloidal mode number m = 2 magnetic islands in agreement with
experiments. We have also extended this analysis by performing a free-boundary transport simulation of an entire
discharge and showing that, with reasonable assumptions, we can predict the time of mode onset.
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Submitted to: Nuclear Fusion (December 2010)
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Download PPPL-4651 (pdf1.33 MB 6 pp)
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