Observation of an impurity hole in a plasma with an ion internal transport barrier in the Large Helical Device

K. Ida, M. Yoshinuma, M. Osakabe, K. Nagaoka, M. Yokoyama, H. Funaba, C. Suzuki, T. Ido, A. Shimizu, I. Murakami, N. Tamura, H. Kasahara, Y. Takeiri, K. Ikeda, K. Tsumori, O. Kaneko, S. Morita, M. Goto, K. Tanaka, K. NariharaT. Minami, I. Yamada

研究成果: ジャーナルへの寄稿記事

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Extremely hollow profiles of impurities (denoted as "impurity hole") are observed in the plasma with a steep gradient of the ion temperature after the formation of an internal transport barrier (ITB) in the ion temperature transport in the Large Helical Device [A. Iiyoshi, Nucl. Fusion 39, 1245 (1999)]. The radial profile of carbon becomes hollow during the ITB phase and the central carbon density keeps dropping and reaches 0.1%-0.3% of plasma density at the end of the ion ITB phase. The diffusion coefficient and the convective velocity of impurities are evaluated from the time evolution of carbon profiles assuming the diffusion and the convection velocity are constant in time after the formation of the ITB. The transport analysis gives a low diffusion of 0.1-0.2 m2 /s and the outward convection velocity of ∼1 m/s at half of the minor radius, which is in contrast to the tendency in tokamak plasmas for the impurity density to increase due to an inward convection and low diffusion in the ITB region. The outward convection is considered to be driven by turbulence because the sign of the convection velocity contradicts the neoclassical theory where a negative electric field and an inward convection are predicted.

元の言語英語
記事番号056111
ジャーナルPhysics of Plasmas
16
発行部数5
DOI
出版物ステータス出版済み - 6 10 2009

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

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    Ida, K., Yoshinuma, M., Osakabe, M., Nagaoka, K., Yokoyama, M., Funaba, H., Suzuki, C., Ido, T., Shimizu, A., Murakami, I., Tamura, N., Kasahara, H., Takeiri, Y., Ikeda, K., Tsumori, K., Kaneko, O., Morita, S., Goto, M., Tanaka, K., ... Yamada, I. (2009). Observation of an impurity hole in a plasma with an ion internal transport barrier in the Large Helical Device. Physics of Plasmas, 16(5), [056111]. https://doi.org/10.1063/1.3111097