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Author(s):
B.J.Peterson, Y.Nakamura, K.Yamazaki, N.Noda, J.Rice, Y.Takeiri, M.Goto, K.Narihara, K.Tanaka, K.Sato, S.Masuzaki, S.Sakakibara, K.Ida, H.Funaba, M.Shoji, M.Osakabe, M.Sato, Yuhong Xu, T.Kobuchi, N.Ashikawa, P.deVries, M.Emoto, H.Idei, K.Ikeda, S.Inagaki, N.Inoue, M.Isobe, S.Kado, K.Khlopenkov, S.Kubo, R.Kumazawa, T.Minami, J.Miyazawa, T.Morisaki, S.Murakami, S.Muto, T.Mutoh, Y.Nagayama, H.Nakanishi, K.Nishimura, T.Notake, Y.Liang, S.Ohdachi, Y.Oka, T.Ozaki, R.O.Pavlichenko, A.Sagara, K.Saito, R.Sakamoto, H.Sasao, M.Sasao, T.Seki, T.Shimozuma, H.Suzuki, M.Takechi, N.Tamura, K.Toi, T.Tokuzawa, Y.Torii, K.Tsumori, I.Yamada, S.Yamaguchi, S.Yamamoto, M.Yokoyama, Y.Yoshimura, K.Y.Watanabe, T.Watari, K.Kawahata, O.Kaneko, N.Ohyabu, H.Yamada, A.Komori, S.Sudo, O.Motojima
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Title:
Impurity Transport Induced Oscillations in LHD
Date of publication:
Sep. 2000
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Key words:
IAEA, fusion energy conference, Sorrento
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Abstract:
In LHD during experiments using stainless steel divertor plates a slow (~ 1 second) cyclic oscillation in the plasma parameters known as 'breathing' plasma was observed during NBI-heated long pulse discharges. The core iron density, calculated from measured parameters using the cooling rate from a corona-equilibrium average-ion model, oscillates out of phase with the electron density. The correlation of the iron impurity concentration with the change in electron termperature and with the local power balance between radiation and beam deposition indicates that when radiation from the iron impurity dominates the local power balance the core plasma is cooled. The increase in the calculated iron density during the phase of the oscillation when the divertor electron temperature exceeds the sputtering threshold suggests that sputtering of the stainless steel divertor plate may be the source of the iron impurity. However the shortness of the delay time raises questions about the causality between these two signals and points to the need for a closer examination of the role of impurity transport in this oscillation.
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