NIFS-657

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Author(s):

M. Sasao, S. Murakami, M. Isobe, A.V. Krasilnikov, S. Iiduka, K. Itoh, N. Nakajima, M. Osakabe, K.Saito,T. Seki, Y.Takeiri, T. Watari, N.Ashikawa , P.deVaries, M.Emoto, H.Funaba, M.Goto, K.Ida, H.Idei, K.Ikeda, S.Inagaki, N.Inoue, S.Kado, O.Kaneko, K.Kawahata, K.Khlopenkov, T.Kobuchi , A.Komori, S.Kubo, R.Kumazawa, S.Masuzaki, T.Minami, J.Miyazawa, T.Morisaki, S.Morita, S.Muto, T.Mutoh, Y.Nagayama, Y.Nakamura, H.Nakanishi, K.Narihara, K.Nishimura, N.Noda, T.Notake, Y.Liang , S.Ohdachi, N.Ohyabu, Y.Oka, T.Ozaki, R.O.Pavlichenko, B.J.Peterson, A.Sagara, S.Sakakibara, R.Sakamoto, H.Sasao, K.Sato, M.Sato, T.Shimozuma, M.Shoji, H.Suzuki, M.Takechi, N.Tamura, K.Tanaka, K.Toi, T.Tokuzawa, Y.Torii, K.Tsumori, H.Yamada, I.Yamada, S.Yamaguchi, S.Yamamoto, M.Yokoyama, Y.Yoshimura, K.Y.Watanabe and O. Motojima

Title:

Study of Energetic Ion Transport in the Large Helical Device

Date of publication:

Sep. 2000

Key words:

IAEA, fusion energy conference, Sorrento

Abstract:

The confinement property of high energy ions and the role of ripple induced transport have been studied in the Large Helical Device (LHD). Tangential beam particles are injected at 90 - 150 kV by negative-ion-based neutral beam injectors, and perpendicular high energy particles are generated by lon Cyclotron Range of Frequency (ICRF) heating. Energy distributions of high energy ions have been measured by fast neutral particle analyzers based on natural diamond detectors, specially developed for this experiment. Time evolution of perpendicular tail temperature in decaying phase after the ICRF termination indicates that the fast particles deeply trapped in helical repples are well confined longer than the collisional relazation time, when n_e > 10^19 m^-3 in the inward shifted configuration (R_ax = 3.6 m). In lower density plasma, however, faster decay than the classical prediction is observed. The tangential energy spectra in a low density steady state plasma of the standard configuration (R_ax=3.75m) also show the deviation from 2D Fokker-Pland simulation. The global 5-D transport simulation code including the ripple induced transport in shows good agreement with measured spectra, and this suggests an important role of ripple induced transport in the standard configuration of LHD.

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