Boundary Perturbations Coupled to Core 3/2 Tearing Modes on the DIII-D Tokamak
Authors: B. Tobias L. Yu, C.W. Domier, N.C. Luhmann, Jr., M.E. Austin, C. Paz-Soldan, A.D. Turnbull, I.G.J. Classen and the DIII-D Team
Abstract:
High confinement (H-mode) discharges on the DIII-D tokamak are routinely
subject to the formation of long-lived, non-disruptive magnetic islands that degrade
confinement and limit fusion performance. Simultaneous, 2D measurement of electron
temperature fluctuations in core and edge regions allows for reconstruction of the radially
resolved poloidal mode number spectrum and phase of the global plasma response
associated with these modes. Coherent, n=2 excursions of the plasma boundary are found
to be the result of coupling to an n=2, kink-like mode which arises locked in phase to the
3/2 island chain. This nonlinear coupling dictates the relative phase of the displacement at
the boundary with respect to the tearing mode. This unambiguous phase relationship, for
which no counter-examples have been observed, is presented as a test for modeling of the
perturbed fields to be expected outside the confined plasma.
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Submitted to: Plasma Physics and Controlled Fusion (March 2013)
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Download PPPL-4879 (pdf 1.23 MB 28 pp)
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