Direct measurements of internal structures of born-locked modes and the key role in triggering tokamak disruptions

X. D. Du; M. W. Shafer; Q. M. Hu; T. E. Evans; E. J. Strait; S. Ohdachi; Y. Suzuki

doi:10.1063/1.5085329

Direct measurements of internal structures of born-locked modes and the key role in triggering tokamak disruptions

X. D. Du, M. W. Shafer, Q. M. Hu, T. E. Evans, E. J. Strait, S. Ohdachi, Y. Suzuki

Advanced Tokamak Physics

Research output: Contribution to journal › Article › peer-review

15 Scopus citations

Abstract

The evolution of the magnetic topology between the outer separatrix of a large m = 2/n = 1 island (m and n: poloidal and toroidal numbers) and the last closed flux surface after mode locking is, for the first time, directly measured. Edge locked island chains with multiple helicity and very narrow widths are discovered to be destabilized and govern the cooling process in the plasma peripheral region. These edge small nonrotating islands are initially well separated from the 2/1 island, leading to a long quasistationary phase, but later trigger thermal quench immediately after they start to overlap with the 2/1 island, producing a broad stochastic layer deep into the plasma midradius.

Original language	English
Article number	042505
Journal	Physics of Plasmas
Volume	26
Issue number	4
DOIs	https://doi.org/10.1063/1.5085329
State	Published - Apr 1 2019

Funding

The author (X. D. Du) would like to thank W. W. Heidbrink, R. J. La Haye, H. Q. Wang, C. Paz-Soldan, and M. A. Van Zeeland for fruitful discussions and encouragement. This work was supported by the U.S. DOE under DE-AC05-00OR22725, DE-FC02-04ER54698, DE-AC02-09CH11466, and DE-SC0015878, JSPS KAKENHI Grant No. JP26249144, and Japan/U.S. Cooperation in Fusion Research and Development. This report was prepared as an account of the work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express, or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DIII-D data shown in this paper can be obtained in digital format by following the links at https://fusion.gat.com/global/D3D_DMP.

Funders	Funder number
U.S. Department of Energy	DE-AC05-00OR22725, DE-SC0015878, DE-AC02-09CH11466, DE-FC02-04ER54698
Japan Society for the Promotion of Science

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abstract = "The evolution of the magnetic topology between the outer separatrix of a large m = 2/n = 1 island (m and n: poloidal and toroidal numbers) and the last closed flux surface after mode locking is, for the first time, directly measured. Edge locked island chains with multiple helicity and very narrow widths are discovered to be destabilized and govern the cooling process in the plasma peripheral region. These edge small nonrotating islands are initially well separated from the 2/1 island, leading to a long quasistationary phase, but later trigger thermal quench immediately after they start to overlap with the 2/1 island, producing a broad stochastic layer deep into the plasma midradius.",

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AU - Du, X. D.

AU - Shafer, M. W.

AU - Hu, Q. M.

AU - Evans, T. E.

AU - Strait, E. J.

AU - Ohdachi, S.

AU - Suzuki, Y.

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AB - The evolution of the magnetic topology between the outer separatrix of a large m = 2/n = 1 island (m and n: poloidal and toroidal numbers) and the last closed flux surface after mode locking is, for the first time, directly measured. Edge locked island chains with multiple helicity and very narrow widths are discovered to be destabilized and govern the cooling process in the plasma peripheral region. These edge small nonrotating islands are initially well separated from the 2/1 island, leading to a long quasistationary phase, but later trigger thermal quench immediately after they start to overlap with the 2/1 island, producing a broad stochastic layer deep into the plasma midradius.

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Direct measurements of internal structures of born-locked modes and the key role in triggering tokamak disruptions

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