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
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Y.S. Park
Columbia University, Columbia U.
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S.A. Sabbagh
Columbia University, PPPL, Columbia U.
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Y.M. Jeon
NFRI, Korea, National Fusion Research Institute, NFRI, Daejeon, South Korea
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S.G. Lee
National Fusion Research Institute, NFRI, Korea
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W.H. Ko
NFRI, Korea, National Fusion Research Institute
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S.H. Hahn
NFRI, Korea
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J.G. Bak
NFRI, Korea, National Fusion Research Institute
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K.-I. You
NFRI, Korea
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J.-K. Park
PPPL, PPPL, Princeton, USA
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M.J. Choi
Postech, Korea
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G.S. Yun
Postech, Korea, Pohang University of Science and Technology
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H.K. Park
POSTECH, Postech, Korea, Pohang University of Science and Technology