Disruptive neoclassical tearing mode seeding in DIII-D with implications for ITER

R. J. La Haye, C. Chrystal, E. J. Strait, J. D. Callen, C. C. Hegna, E. C. Howell, M. Okabayashi, R. S. Wilcox

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

New studies identify the critical parameters and physics governing disruptive neoclassical tearing mode (NTM) onset. An m/n = 2/1 mode in DIII-D that begins to grow robustly after a seeding event (edge localized mode ELM or sawtooth precursor and crash) causes the mode rotation to drop close to the plasma's E r = 0 rest frame; this condition opens the stabilizing ion-polarization current 'gate' and destabilizes an otherwise marginally stable NTM. Our new experimental and theoretical insights and novel toroidal theory-based modeling are benchmarked and scalable to ITER and other future experiments. The nominal ITER rotation at q = 2 is found to be stabilizing ('gate closed') except for MHD-induced transients that could 'open the gate'. Extrapolating from the DIII-D ITER baseline scenario (IBS) discharges, MHD transients are much more likely to destabilize problematic robustly growing 2/1 NTMs in ITER; this makes predictions of seeding and control of both ELMs and sawteeth imperative for more than just minimizing divertor pulsed-heat loading.

Original languageEnglish
Article number056017
JournalNuclear Fusion
Volume62
Issue number5
DOIs
StatePublished - May 2022

Funding

This material is based upon work supported by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award(s) DE-FC02-04ER54698, DE-FG02-86ER53218, DE-AC05-00OR22725, DE-AC02-09CH11466 and DE-SC0018313. N.Z. Taylor is thanked for leading the session on DIII-D to get fast CER data. Z.R. Wang is thanked for the Resistive DCON tearing stability code analysis. A.R. Polevoi is thanked for help in getting the ITER parameters.

Keywords

  • stability
  • tearing
  • tokamak

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