A new stabilizing regime of tearing mode entrainment in the presence of a static error field

M. Okabayashi, S. Inoue, N. C. Logan, N. Z. Taylor, E. J. Strait, J. De Grassie, N. Ferraro, J. Hanson, S. Jardin, R. J. La Haye, Y. Q. Liu, C. Paz-Soldan, L. Sugiyama, A. Wingen

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Uncorrected static error fields (EFs) in axisymmetric fusion devices are one of the few remaining serious obstacles for advancing the present tokamak-based approach to a practical reactor. Magnetohydrodynamic tearing modes (TMs) lock to them, causing sudden losses of confinement known as disruptions. Recently, a hypothesis has been proposed that there may exist a self-healing stable regime in which a static resonant EF is effectively shielded by forcing these TMs to slowly rotate inductively by the applied non-axisymmetric field (Inoue et al 2017 Nucl. Fusion 57 116020; Inoue et al 2018 Plasma. Phys. Control. Fusion 60 025003; Inoue et al 2018 Preprint: 2018 IAEA Fusion Energy Conf. TH/P4-24). This is based on non-linear, resistive, reduced magnetohydrodynamic simulations using a cylindrical single helicity model. Proof-of-principle experiments in the DIII-D device showed that the magnetic mode structure on the plasma surface is qualitatively consistent with the simulation prediction. However, radial mode profiles revealed qualitatively different behavior. This led to a revised hypothesis that in actual non-circular toroidal devices, a tearing layer in forced rotation induces a shielding process at other rational surfaces when we take into account multiple resonant Fourier components. The time evolution experiment of the radial penetration is supportive of this hypothesis.

Original languageEnglish
Article number126015
JournalNuclear Fusion
Volume59
Issue number12
DOIs
StatePublished - Sep 30 2019

Keywords

  • bifurcation
  • disruption
  • tearing mode locking

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