KSTAR stability and rotation control results for high normalized beta plasmas exceeding the ideal MHD no-wall stability limit

POSTER

Abstract

Plasma stability parameters in KSTAR have reached and exceeded the $n$~$=$~1 ideal no-wall limit computed for H-mode profiles. Normalized beta up to 2.9 has been achieved and sustained with plasma internal inductance near 0.75. The ratio $\beta_{N}$/$l_{i}$ has exceeded 3.6 (an 80{\%} increase over the prior year). Plasma stored energy has exceeded 0.5~MJ. Non-axisymmetric field spectra with dominant $n$~$=$~2 component were applied to alter the plasma rotation profile by non-resonant neoclassical toroidal viscosity (NTV). The rotation profile was significantly altered without tearing activity or mode locking. Changing the in-vessel control coil current in steps altered rotation in a controlled fashion without hysteresis. The core rotation was lowered by 50{\%} as measured by charge exchange spectroscopy, x-ray crystal spectrometer, and supported by magnetic diagnostics. H-mode energy confinement was maintained at reduced rotation while the resultant profile was peaked, as found in L-mode. Tearing mode onset conditions and mode locking criteria due to the applied $n$~$=$~1,~2 applied fields were investigated. Additionally, ELMs were mitigated using sufficient $n$~$=$~2 field strength by using midplane coils alone. Advances from the recent run campaign will be reported.

Authors

  • Y.S. Park

    Columbia University, Columbia U.

  • S.A. Sabbagh

    Columbia University, PPPL, Columbia U.

  • Y.M. Jeon

    NFRI, Korea, National Fusion Research Institute, NFRI, Daejeon, South Korea

  • S.G. Lee

    National Fusion Research Institute, NFRI, Korea

  • W.H. Ko

    NFRI, Korea, National Fusion Research Institute

  • S.H. Hahn

    NFRI, Korea

  • J.G. Bak

    NFRI, Korea, National Fusion Research Institute

  • K.-I. You

    NFRI, Korea

  • J.-K. Park

    PPPL, PPPL, Princeton, USA

  • M.J. Choi

    Postech, Korea

  • G.S. Yun

    Postech, Korea, Pohang University of Science and Technology

  • H.K. Park

    POSTECH, Postech, Korea, Pohang University of Science and Technology