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Author(s):
S. Kobayashi, T. Mizuuchi, K. Nagasaki, H. Okada, K. Kondo, S. Yamamoto, S. Murakami, D. Katayama, Y. Suzuki, T. Minami, K. Nagaoka, Y. Takeiri, K. Murai, Y. Nakamura, M. Yokoyama, K. Hanatani, G. Motojima, K. Hosaka, K. Toushi, F. Sano
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Title:
Effect of Bumpy Magnetic Field on Energy Confinement in NBI Plasmas of Heliotron J
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Date of publication:
Oct. 2008
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Key words:
21 IAEA Fusion Energy Conference, EX/P5-13
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Abstract:
The energy confinement in the NBI plasmas has been investigated in the helical-axis heliotron device, Heliotron J. The configuration control experiments for bumpiness (epsilon_b), being one of the side-bands of the helical component, show that the plasma performance in NBI plasmas depends on not only the effective helical ripple (epsilon_eff) but also the bumpiness. The preferable enhancement factor of the experimental energy confinement time to the international stellarator scaling law ISS95 has been obtained in the high- epsilon_b configuration and in the low- epsilon _eff (i.e. medium- epsilon_b ) condition. The improvement in the ion and electron temperature contributes to the enhancement of the plasma performance in the high- epsilon_b configurations since the fast ion confinement is found to be better in this configuration. The control of bumpiness is effective not only in the energetic particle transport but also in the global energy confinement in NBI plasmas of Heliotron J.
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