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(EX/P2-16) Radial Electric Field and Transport near the Rational Surface and the Magnetic Island in LHD

K. Ida¹⁾, S. Inagaki¹⁾, N. Tamura¹⁾, T. Morisaki¹⁾, N. Ohyabu¹⁾, K. Khlopenkov¹⁾, S. Sudo¹⁾, K. Watanabe¹⁾, M. Yokoyama¹⁾, T. Shimozuma¹⁾, Y. Takeiri¹⁾, K. Itoh¹⁾, M. Yoshinuma¹⁾, Y. Liang¹⁾, K. Narihara¹⁾, K. Tanaka¹⁾, Y. Nagayama¹⁾, T. Tokuzawa¹⁾, K. Kawahata¹⁾, H. Suzuki¹⁾, A. Komori¹⁾, T. Akiyama²⁾, N. Ashikawa¹⁾, M. Emoto¹⁾, H. Funaba¹⁾, P. Goncharov³⁾, M. Goto¹⁾, H. Idei¹⁾, K. Ikeda¹⁾, M. Isobe¹⁾, O. Kaneko¹⁾, H. Kawazome⁴⁾, T. Kobuchi¹⁾, A. Kostrioukov¹⁾, S. Kubo¹⁾, R. Kumazawa¹⁾, S. Masuzaki¹⁾, T. Minami¹⁾, J. Miyazawa¹⁾, S. Morita¹⁾, S. Murakami¹⁾, S. Muto¹⁾, T. Mutoh¹⁾, Y. Nakamura¹⁾, H. Nakanishi¹⁾, Y. Narushima¹⁾, K. Nishimura¹⁾, N. Noda¹⁾, T. Notake⁵⁾, H. Nozato⁶⁾, S. Ohdachi¹⁾, Y. Oka¹⁾, M. Osakabe¹⁾, T. Ozaki¹⁾, B.J. Peterson¹⁾, A. Sagara¹⁾, T. Saida³⁾, K. Saito¹⁾, S. Sakakibara¹⁾, R. Sakamoto¹⁾, M. Sasao¹⁾, K. Sato¹⁾, M. Sato¹⁾, T. Seki¹⁾, M. Shoji¹⁾, N. Takeuchi⁵⁾, K. Toi¹⁾, Y. Torii⁵⁾, K. Tsumori¹⁾, T. Watari¹⁾, Y. Xu¹⁾, H. Yamada¹⁾, I. Yamada¹⁾, S. Yamamoto⁵⁾, T. Yamamoto⁵⁾, Y. Yoshimura¹⁾, I. Ohtake¹⁾, K. Ohkubo¹⁾, T. Mito¹⁾, T. Satow¹⁾, T. Uda¹⁾, K. Yamazaki¹⁾, K. Matsuoka¹⁾, O. Motojima¹⁾, M. Fujiwara^1)
 
1) National Institute for Fusion Science, Toki, Japan
²⁾ Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo, Japan
³⁾ Department of Fusion Science, School of Mathematical and Physical Science, Graduate University for Advanced Studies, Hayama, Japan
⁴⁾ Graduate School of Energy Science, Kyoto University, Uji, Japan
⁵⁾ Department of Energy Engineering and Science, Nagoya University, Japan
⁶⁾ Graduate School of Frontier Sciences, The University of Tokyo, Japan

Abstract.  The structures of radial electric field and transport at the magnetic island are investigated using n/m=1/1 external perturbation coils in the Large Helical Device (LHD). The radial profiles of plasma potential, as well as the electron temperature and density, shows flattening inside the magnetic island and the large shear of the radial electric field is observed at the boundary of the magnetic island. When the current of n/m=1/1 external perturbation coils becomes large enough, the finite radial electric field appears inside the magnetic island. The abrupt appearance of plasma flow inside the magnetic island suggests the non-linearity of the viscous force at the boundary of the magnetic island. The thermal diffusivity perpendicular to the magnetic filed inside the magnetic island is estimated with the cold pulse propagation, which is produced by a tracer-encapsulated solid pellet (TESPEL). The time delay and amplitude of the electron temperature of the cold pulse show much lower thermal diffusivity inside the magnetic island ( 0.3m²/s) than that outside the magnetic island ( 6m²/s), which is a clear evidence for the significant reduction of heat transport inside the magnetic island.

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