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Author(s):
Y. Nakamura, Y. Takeiri, R. Kumazawa, M. Osakabe, T. Seki, B. J. Peterson, K. Ida, N. Tamura, A. Komori, S. Morita, K. Narihara, Y. Nagayama, K. Sato, T. Tokuzawa, N. Noda, T. Mutoh, T. Shimozuma, K. Kawahata, H. Funaba, M. Goto, K. Ikeda, S. Inagaki, S. Masuzaki, J. Miyazawa, T. Morisaki, S. Muto, Y. Oka, S. Sakakibara, H. Suzuki, K. Tanaka, T. Watari, H. Yamada, M. Yokoyama, Y. Yoshimura, N. Ohyabu, S. Sudo, K. Matsuoka, O. Motojima and LHD Experimental Group
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Title:
Plasma Performance and Impurity Behavior in Long Pulse Discharges on LHD
Date of publication:
Oct. 2002
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Key words:
IAEA, fusion energy conference, Lyon
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Abstract:
The superconducting machine LHD has conducted long pulse experiments for four years to achieve long-duration plasmas with high performance. The operational regime was largely extended in the discharge duration and the plasma density. In this paper, the plasma characteristics, in particular, plasma performance and impurity behavior in long pulse discharges are described. Confnement studies show that global energy confinement times are compared with those in short-pulse discharges. Long sustainment of high performance plasma, which is equivalent to the previous achievement in other devices, was demonstrated. Long pulse discharges enabled us to investigate impurity behavior in a long time-scale. Intrinsic metallic impurity accumulation was observed in a narrow density window (2~3 x 10^19 m^-3) only for hydrogen discharges. Finally, impurity accumulation control with an externally induced magnetic island at the plasma edge was demonstrated.
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