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Solitary perturbations in the steep boundary of magnetized toroidal plasma. Sci Rep 2017; 7:45075. [PMID: 28338046 PMCID: PMC5364482 DOI: 10.1038/srep45075] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 02/20/2017] [Indexed: 11/08/2022] Open
Abstract
Solitary perturbations (SPs) localized both poloidally and radially are detected within ~100 μs before the partial collapse of the high pressure gradient boundary region (called pedestal) of magnetized toroidal plasma in the KSTAR tokamak device. The SP develops with a low toroidal mode number (typically unity) in the pedestal ingrained with quasi-stable edge-localized mode (QSM) which commonly appears during the inter-collapse period. The SPs have smaller mode pitch and different (often opposite) rotation velocity compared to the QSMs. Similar solitary perturbations are also frequently observed before the onset of complete pedestal collapse, suggesting a strong connection between the SP generation and the pedestal collapse.
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Lee J, Yun GS, Choi MJ, Kwon JM, Jeon YM, Lee W, Luhmann NC, Park HK. Nonlinear Interaction of Edge-Localized Modes and Turbulent Eddies in Toroidal Plasma under n=1 Magnetic Perturbation. PHYSICAL REVIEW LETTERS 2016; 117:075001. [PMID: 27563970 DOI: 10.1103/physrevlett.117.075001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Indexed: 06/06/2023]
Abstract
The effect of static n=1 resonant magnetic perturbation (RMP) on the spatial structure and temporal dynamics of edge-localized modes (ELMs) and edge turbulence in tokamak plasma has been investigated. Two-dimensional images measured by a millimeter-wave camera on the KSTAR tokamak revealed that the coherent filamentary modes (i.e., ELMs) are still present in the edge region when the usual large scale collapse of the edge confinement, i.e., the ELM crash, is completely suppressed by n=1 RMP. Cross-correlation analyses on the 2D images show that (1) the RMP enhances turbulent fluctuations in the edge toward the ELM-crash-suppression phase, (2) the induced turbulence has a clear dispersion relation for wide ranges of wave number and frequency, and (3) the turbulence involves a net radially outward energy transport. Nonlinear interactions of the turbulent eddies with the coexisting ELMs are clearly observed by bispectral analysis, which implies that the exchange of energy between them may be the key to the prevention of large scale crashes.
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Affiliation(s)
- Jaehyun Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Gunsu S Yun
- Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Minjun J Choi
- National Fusion Research Institute, Daejeon 34133, Republic of Korea
| | - Jae-Min Kwon
- National Fusion Research Institute, Daejeon 34133, Republic of Korea
| | - Young-Mu Jeon
- National Fusion Research Institute, Daejeon 34133, Republic of Korea
| | - Woochang Lee
- Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | | | - Hyeon K Park
- Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
- National Fusion Research Institute, Daejeon 34133, Republic of Korea
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Yun GS, Lee W, Choi MJ, Lee J, Kim M, Leem J, Nam Y, Choe GH, Park HK, Park H, Woo DS, Kim KW, Domier CW, Luhmann NC, Ito N, Mase A, Lee SG. Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:11D820. [PMID: 25430233 DOI: 10.1063/1.4890401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A second electron cyclotron emission imaging (ECEI) system has been installed on the KSTAR tokamak, toroidally separated by 1/16th of the torus from the first ECEI system. For the first time, the dynamical evolutions of MHD instabilities from the plasma core to the edge have been visualized in quasi-3D for a wide range of the KSTAR operation (B0 = 1.7∼3.5 T). This flexible diagnostic capability has been realized by substantial improvements in large-aperture quasi-optical microwave components including the development of broad-band polarization rotators for imaging of the fundamental ordinary ECE as well as the usual 2nd harmonic extraordinary ECE.
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Affiliation(s)
- G S Yun
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - W Lee
- Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea
| | - M J Choi
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - J Lee
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - M Kim
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - J Leem
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Y Nam
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - G H Choe
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - H K Park
- Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea
| | - H Park
- School of Electrical Engineering, Kyungpook National University, Daegu 702-701, Korea
| | - D S Woo
- School of Electrical Engineering, Kyungpook National University, Daegu 702-701, Korea
| | - K W Kim
- School of Electrical Engineering, Kyungpook National University, Daegu 702-701, Korea
| | - C W Domier
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - N C Luhmann
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, USA
| | - N Ito
- KASTEC, Kyushu University, Kasuga-shi, Fukuoka 812-8581, Japan
| | - A Mase
- Ube National College of Technology, Ube-shi, Yamaguchi 755-8555, Japan
| | - S G Lee
- National Fusion Research Institute, Daejeon 305-333, Korea
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