Novel intrinsic helical cores and MHD dynamo flux pumping evidence in DIII-D

Boyes, W.; Turco, F.; Hanson, J.; Navratil, G. A.; Turnbull, A.; Hyatt, A.; Luce, T.; Meyer, W.; Nelson, A. O.; Odstrcil, T.; Osborne, T.; Scotti, F.; Welander, A.; Wingen, Andreas

doi:10.1088/1741-4326/ad89d9

Title: Novel intrinsic helical cores and MHD dynamo flux pumping evidence in DIII-D

Journal Article · 01 November 2024 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/ad89d9 · OSTI ID:2475850

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^[1]; Turnbull, A. ^[2]; Hyatt, A. ^[2]; Luce, T. ^[3]; Meyer, W. ^[4];

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^[2]; Scotti, F. ^[4]; Welander, A. ^[2];

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Columbia University, New York, NY (United States)
General Atomics, San Diego, CA (United States)
ITER Organization, Saint Paul Lez Durance (France)
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Evidence of a MHD dynamo brought about by intrinsic helical core structures in negative triangularity (NT) and ITER baseline scenario (IBS) plasmas demonstrates paths to operating tokamaks without seeds for deleterious global MHD modes. A stationary sawtooth- and edge localized mode-free state maintains high performance for long durations in a strong NT shape in the DIII-D tokamak. Disparity between minimum safety factor values predicted by magnetic flux diffusion theory and derived from experiment suggests anomalous flux diffusion by an MHD dynamo, driven by flows associated with quasi-interchange modes. Stability calculations with the GATO code find NT and IBS experimental equilibria unstable to quasi-interchange modes, in agreement with observed saturated activity. IBS discharges with similar magnetic winding structure occupy robust helical core states following a transition from sawtooth instabilities. These states agree with prior modeling of helical core bifurcation thresholds with the VMEC equilibrium code.

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Research Organization:: General Atomics, San Diego, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE; USDOE Office of Science (SC); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: AC05-00OR22725; AC52-07NA27344; FC02-04ER54698; FG02-04ER54761; SC0022270; SC0022272

OSTI ID:: 2475850

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 12 Vol. 64; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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