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Title: Predicting operational windows of ELMs suppression by resonant magnetic perturbations in the DIII-D and KSTAR tokamaks

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/5.0043018· OSTI ID:1781666
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [3]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [4]; ORCiD logo [5]; ORCiD logo [5]; ORCiD logo [6]; ORCiD logo [7];  [5]; ORCiD logo [8]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Columbia Univ., New York, NY (United States)
  4. Korea Inst. of Fusion Energy, Daejeon (South Korea); Ulsan National Inst. of Science and Technology (South Korea)
  5. Korea Inst. of Fusion Energy, Daejeon (South Korea)
  6. Princeton Univ., NJ (United States)
  7. Univ. of California, San Diego, CA (United States)
  8. Max-Plank-Inst. fur Plasmaphysik, Garching (Germany)

A newly developed plasma response model, combining the nonlinear two-fluid MHD code TM1 and toroidal MHD code GPEC run in ideal mode, quantitatively predicts the narrow isolated q95 windows (Δq95 ~ 0.1) of ELM suppression by n = 1, 2 and 3 resonant magnetic perturbations (RMPs) in both DIII-D and KSTAR tokamaks across a wide range of plasma parameters. The key physics that unites both experimental observations and our simulations is the close alignment of essential resonant q-surfaces and the location of the top of the pedestal prior to an ELM. This alignment permits an applied RMP to produce field penetration due to the lower E × B rotation at the pedestal top rather than being screened. The model successfully predicts that narrow magnetic islands form when resonant field penetration occurs at the top of pedestal, and these islands are easily screened when q95 moves off resonance, leading to very narrow windows of ELM suppression (typically Δq95 ~ 0.1). Furthermore, the observed reduction in the pedestal height is also well captured by the calculated classical collisional transport across the island. We recover observed q95, βN and plasma shape dependence of ELM suppression due to the effect of magnetic islands on pedestal transport and Peeling-Ballooning- Mode (PBM) stability. Importantly, experiments do occasionally observe wide windows of ELM suppression (Δq95 > 0.5). Our model reveals that at low pedestal-top density multiple islands open, leading to wide operational windows of ELM suppression consistent with experiment. The model indicates that wide q95 windows of ELM suppression can be achieved at substantially higher pedestal pressure with less confinement degradation in DIII-D by operating at higher toroidal mode number (n = 4) RMPs. As a result, this can have significant implications for the operation of the ITER ELM control coils for maintaining high confinement together with ELM suppression.

Research Organization:
General Atomics, San Diego, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Grant/Contract Number:
FC02-04ER54698; AC02-09CH11466; FG02-05ER54809; No. EN2101-12; AC52-07NA27344
OSTI ID:
1781666
Alternate ID(s):
OSTI ID: 1781969; OSTI ID: 1808312; OSTI ID: 1828673
Report Number(s):
LLNL-JRNL-828233; TRN: US2209946
Journal Information:
Physics of Plasmas, Vol. 28, Issue 5; ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English

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