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Analysis on the access condition to hybrid scenario in KSTAR

ORAL

Abstract

 After the successful operation of hybrid scenarios with a stationary performance of βN ≤ 3.0 and H89 ≤ 2.4 with the limited heating power Paux < 4.5MW [1], several experiments have been attempted to identify the robust access condition to the high-performance hybrid scenarios. In the 2020 campaign, it was found that the discharges with relatively high Dα baseline level and line averaged density could achieve the high performance after a performance bifurcation while other conditions were similar. The major cause is found to be the excitation of the edge localized coherent mode with mode number of n=6 and following broad-band fluctuations growing in the inter-ELM crashes. They enhance the transport in the edge region, which widens the pedestal and reduces its gradient, leading to the higher pedestal pressure [2]. Dedicated experiments to scan D2 fueling at the divertor region (using PVD) reveal that the increase of the Dα baseline level and edge density not only extied the edge localized coherent mode and broad-band fluctuations but also reproduce the high performance. 

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Publication: [1] Na, Yong-Su, et al. "On hybrid scenarios in KSTAR." Nuclear Fusion 60.8 (2020): 086006.<br>[2] Chen, Xi, et al. "Bifurcation of quiescent H-mode to a wide pedestal regime in DIII-D and advances in the understanding of edge harmonic oscillations." Nuclear Fusion 57.8 (2017): 086008.

Presenters

  • Youngho Lee

    Korea Institute of Fusion Energy (KFE), Korea Institute of Fusion Energy, Korea Institute of Fusion Energy, Daejeon, Korea

Authors

  • Youngho Lee

    Korea Institute of Fusion Energy (KFE), Korea Institute of Fusion Energy, Korea Institute of Fusion Energy, Daejeon, Korea

  • SangKyeun Kim

    Princeton University, Princeton Plasma Physics Laboratory, Princeton University, Princeton, U.S.A.

  • Jaewook Kim

    Korea Institute of Fusion Energy, Korea Institute of Fusion Energy, Daejeon, Korea, Korea institute of Fusion Energy, Korea Institute of Fusion Energy (KFE)

  • Minseo Park

    Seoul National University, Seoul National University, Seoul, Korea

  • Sang-hee Hahn

    Korea Institute of Fusion Energy, Korea Institute of Fusion Energy (KFE), KFE, Korea Institute of Fusion Energy, Daejeon, Korea

  • Boseong Kim

    Seoul National University, Seoul National University, Seoul, Korea

  • SeongMoo Yang

    Princeton Plasma Physics Laboratory, Princeton Plasma Physics Laboratory, Princeton, U.S.A.

  • Cheol-Sik Byun

    Seoul National University, Seoul, Korea

  • Woochang Lee

    Korea Institute of Fusion Energy, Daejeon, Korea

  • SeulChan Hong

    Korea Institute of Fusion Energy, Daejeon, Korea

  • Chan-Young Lee

    Seoul National University, Seoul National University, Seoul, Korea

  • Sangjin Park

    Seoul National University, Seoul National University, Seoul, Korea

  • Yong-Su Na

    Seoul National University, Seoul National University, Seoul, Korea