Impact of E × B shear flow on low-n MHD instabilities

Chen, J. G.; Xu, X. Q.; Ma, C. H.; Xi, P. W.; Kong, D. F.; Lei, Y. A.

doi:10.1063/1.4984257

Title: Impact of E × B shear flow on low-n MHD instabilities

Journal Article · Wed May 24 00:00:00 EDT 2017 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4984257· OSTI ID:1566033

Chen, J. G. ^[1];

^[2]; Ma, C. H. ^[3]; Xi, P. W. ^[3];

^[4]; Lei, Y. A. ^[1]

Peking Univ., Beijing (China). School of Physics, State Key Lab. of Nuclear Physics
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Peking Univ., Beijing (China). School of Physics, State Key Lab. of Nuclear Physics; Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics

Recently, the stationary high confinement operations with improved pedestal conditions have been achieved in DIII-D [K. H. Burrell et al., Phys. Plasmas 23, 056103 (2016)], accompanying the spontaneous transition from the coherent edge harmonic oscillation (EHO) to the broadband MHD turbulence state by reducing the neutral beam injection torque to zero. It is crucial for the burning plasma devices such as ITER. Simulations about the effects of E×B shear flow on the quiescent H-mode (QH-mode) are carried out using the three-field two-fluid model in the field-aligned coordinate under the BOUT++ framework. Using the shifted circular cross-section equilibriums including bootstrap current, the results demonstrate that the E×B shear flow strongly destabilizes low-n peeling modes, which are mainly driven by the gradient of parallel current in peeling-dominant cases and are sensitive to the E_r shear. Adopting the much more general shape of E×B shear (ω_E=E_r/RB_θ) profiles, the linear and nonlinear BOUT++ simulations show qualitative consistence with the experiments. The stronger shear flow shifts the most unstable mode to lower-n and narrows the mode spectrum. At the meantime, the nonlinear simulations of the QH-mode indicate that the shear flow in both co- and counter directions of diamagnetic flow has some similar effects. The nonlinear mode interaction is enhanced during the mode amplitude saturation phase. These findings reveal that the fundamental physics mechanism of the QH-mode may be shear flow and are significant for understanding the mechanism of EHO and QH-mode.

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Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: AC52-07NA27344; AC52-7NA27344

OSTI ID:: 1566033

Alternate ID(s):: OSTI ID: 1375646

Report Number(s):: LLNL-JRNL-721760; 868466; TRN: US2000963

Journal Information:: Physics of Plasmas, Vol. 24, Issue 5; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 19 works

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