Configuration flexibility and extended regimes in Large Helical Device

H. Yamada, A. Komori, N. Ohyabu, O. Kaneko, K. Kawahata, K. Y. Watanabe, S. Sakakibara, S. Murakami, K. Ida, R. Sakamoto, Y. Liang, J. Miyazawa, K. Tanaka, Y. Narushima, S. Morita, S. Masuzaki, T. Morisaki, N. Ashikawa, L. R. Baylor, W. A. CooperM. Emoto, P. W. Fisher, H. Funaba, M. Goto, H. Idei, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, K. Khlopenkov, T. Kobuchi, A. Kostrioukov, S. Kubo, T. Kuroda, R. Kumazawa, T. Minami, S. Muto, T. Mutoh, Y. Nagayama, N. Nakajima, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Notake, S. Ohdachi, Y. Oka, M. Osakabe, T. Ozaki, B. J. Peterson, G. Rewoldt, A. Sagara, K. Saito, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, H. Sugama, T. Shimozuma, M. Shoji, H. Suzuki, Y. Takeiri, N. Tamura, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, T. Watanabe, I. Yamada, S. Yamamoto, M. Yokoyama, Y. Yoshimura, T. Watari, Y. Xu, K. Itoh, K. Matsuoka, K. Ohkubo, T. Satow, S. Sudo, T. Uda, K. Yamazaki, O. Motojima, M. Fujiwara

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97 Citations (Scopus)


Recent experimental results in the Large Helical Device have indicated that a large pressure gradient can be formed beyond the stability criterion for the Mercier (high-n) mode. While the stability against an interchange mode is violated in the inward-shifted configuration due to an enhancement of the magnetic hill, the neoclassical transport and confinement of high-energy particle are, in contrast, improved by this inward shift. Mitigation of the unfavourable effects of MHD instability has led to a significant extension of the operational regime. Achievements of the stored energy of 1 MJ and the volume-averaged beta of 3% are representative results from this finding. A confinement enhancement factor above the international stellarator scaling ISS95 is also maintained around 1.5 towards a volume-averaged beta, 〈β〉, of 3%. Configuration studies on confinement and MHD characteristics emphasize the superiority of the inward-shifted geometry to other geometries. The emergence of coherent modes appears to be consistent with the linear ideal MHD theory; however, the inward-shifted configuration has reduced heat transport in spite of a larger amplitude of magnetic fluctuation than the outward-shifted configuration. While neoclassical helical ripple transport becomes visible for the outward-shifted configuration in the collisionless regime, the inward-shifted configuration does not show any degradation of confinement deep in the collisionless regime (v* < 0.1). The distinguished characteristics observed in the inward-shifted configuration help in creating a new perspective of MHD stability and related transport in net current-free plasmas. The first result of the pellet launching at different locations is also reported.

Original languageEnglish
Pages (from-to)A55-A71
JournalPlasma Physics and Controlled Fusion
Issue number12A
Publication statusPublished - 2001
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics


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