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(EXP5/27) Impurity Transport Induced Oscillations in LHD

B. J. Peterson¹⁾, Y. Nakamura¹⁾, K. Yamazaki¹⁾, N. Noda¹⁾, J. Rice²⁾, Y. Takeiri¹⁾, M. Goto¹⁾, K. Narihara¹⁾, K. Tanaka¹⁾, K. Sato¹⁾, S. Masuzaki¹⁾, S. Sakakibara¹⁾, K. Ida¹⁾, H. Funaba¹⁾, M. Shoji¹⁾, M. Osakabe¹⁾, M. Sato¹⁾, Y. Xu¹⁾, T. Kobuchi³⁾, N. Ashikawa³⁾, P. de Vries¹⁾, M. Emoto¹⁾, H. Idei¹⁾, K. Ikeda¹⁾, S. Inagaki¹⁾, N. Inoue¹⁾, M. Isobe¹⁾, S. Kado¹⁾, K. Khlopenkov¹⁾, S. Kubo¹⁾, R. Kumazawa¹⁾, T. Minami¹⁾, J. Miyazawa¹⁾, T. Morisaki¹⁾, S. Murakami¹⁾, S. Muto¹⁾, T. Mutoh¹⁾, Y. Nagayama¹⁾, H. Nakanishi¹⁾, K. Nishimura¹⁾, T. Notake⁴⁾, Y. Liang³⁾, S. Ohdachi¹⁾, Y. Oka¹⁾, T. Ozaki¹⁾, R. O. Pavlichenko¹⁾, A. Sagara¹⁾, K. Saito⁴⁾, R. Sakamoto¹⁾, H. Sasao³⁾, M. Sasao¹⁾, T. Seki¹⁾, T. Shimozuma¹⁾, H. Suzuki¹⁾, M. Takechi¹⁾, N. Tamura³⁾, K. Toi¹⁾, T. Tokuzawa¹⁾, Y. Torii⁴⁾, K. Tsumori¹⁾, I. Yamada¹⁾, S. Yamaguchi¹⁾, S. Yamamoto⁴⁾, M. Yokoyama¹⁾, Y. Yoshimura¹⁾, K. Y. Watanabe¹⁾, T. Watari¹⁾, K. Kawahata¹⁾, O. Kaneko¹⁾, N. Ohyabu¹⁾, H. Yamada¹⁾, A. Komori¹⁾, S. Sudo¹⁾, O. Motojima^1)
 
1) National Institute for Fusion Science, Toki-shi 509-5292, JAPAN
²⁾ Plasma Science & Fusion Center, Mass. Inst. of Tech., Cambridge, MA 02139 , USA
³⁾ Dept. of Fusion Science, School of Math. and Phys. Science, Grad. Univ. for Adv. Studies, Hayama 240-0193, Japan
⁴⁾ Dept.of Energy Engineering and Science, Nagoya Univ., Nagoya 464-8603, Japan

Abstract.  In LHD during experiments using stainless steel divertor plates a slow ($\sim$ 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 temperature 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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