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Author(s):
K. Saito, R. Kumazawa, T. Mutoh, T. Seki, T. Watari, T. Yamamoto, Y. Torii, N. Takeuchi C. Zhang, Y. Zhao, A. Fukuyama, F. Shimpo, G. Nomura, M. Yokota, A. Kato, M. Sasao, M. Isobe, A.V. Krasilnikov, T. Ozaki, M. Osakabe, K. Narihara, Y. Nagayama, S. Inagaki, K. Itoh, T. Ido, S. Morita, K. Ohkubo, M. Sato, S. Kubo, T. Shimozuma, H. Idei, Y. Yoshimura, T. Notake, O. Kaneko, Y. Takeiri, Y. Oka, K. Tsumori, K. Ikeda, A. Komori, H. Yamada, H. Funaba, K.Y. Watanabe, S. Sakakibara, R. Sakamoto, J. Miyazawa, K. Tanaka, B.J. Peterson, N. Ashikawa, S. Murakami, T. Minami, M. Shoji, S. Ohdachi, S. Yamamoto, H. Suzuki, K. Kawahata, M. Emoto, H. Nakanishi, N. Inoue, N. Ohyabu, Y. Nakamura, S. Masuzaki, S. Muto, K. Sato, T. Morisaki, M. Yokoyama, T. Watanabe, M. Goto, I. Yamada, K. Ida, T. Tokuzawa, N. Noda, K. Toi, S. Yamaguchi, K. Akaishi, A. Sagara, K. Nishimura, K. Yamazaki, S. Sudo, Y. Hamada, O. Motojima, M. Fujiwara
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Title:
A Study of High-Energy Ions Produced by ICRF Heating in LHD
Date of publication:
Sep. 2001
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Key words:
ICRF heating, high-energy ions, power modulation, anisotropy of distribution function, second harmonic heating, LHD
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Abstract:
This paper reports on the behavior of high-energy ions produced by Ion Cyclotron Range of Frequency (ICRF) heating on the Large Helical Device (LHD). In the 3rd experimental campaign conducted in1999, it was shown that minority heating has high heating efficiency, and high-energy particles were also observed. In the 4th campaign in 2000 the temporal behavior of high-energy ions was investigated in the minority heating regime using turn-off or modulation of ICRF power. The time evolution of the high-energy particle distribution was measured using a natural diamond detector (NDD) and a time-of-flight neutral particle analyzer (TOF-NPA). It was found that the count number of higher-energy particles declines faster than that of lower-energy particles after ICRF turn-off. In the modulation experiments, the phase difference of the flux of high-energy particles with respect to the ICRF power modulation increased with energy. These results were explained qualitatively by the Fokker-Planck equation with a simple model. The pitch-angle dependence of the distribution function was also measured in the experiment by changing the line of sight of the TOF-NPA and an anisotropy of the high-energy tail was found. This anisotropy was reproduced by solving the bounce-averaged Fokker-Planck equation. The second harmonic heating was conducted successfully for the first time during high beta plasma experiments in the LHD. High-energy particles were also detected in this heating regime.
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