@techreport{oai:nifs-repository.repo.nii.ac.jp:00009570, author = {"Fukuda, T. and Tamura, N. and Ida, K. and Michael, C. and Tanaka, K. and Vyacheslavov, L. N. and Yoshinuma, M. and Kobuchi, T. and Watanabe, K. Y. and Funaba, H. and Igami, H. and Itoh, K. and Ido, T. and Inagaki, S. and Oishi, T. and Kato, T. and Kado, S. and Kubo, S. and Goto, M. and Sakamoto, R. and Satake, S. and Shimizu, A. and Shimozuma, T. and Suzuki, C. and Sudo, S. and Takeiri, Y. and Toi, K. and Tokuzawa, T. and Nakano, H. and Narihara, K. and Nishimura, S. and Notake, T. and Minami, T. and Muto, S. and Morita, S. and Liu, Y. and Pavlichenco, R. and Yamada, H. and Yamada, I. and Yokoyama, M. and Kawahata, K. and Komori, A. and the, LHD experimental group"}, month = {Oct}, note = {"For the comprehensive understandings of transport phenomena in toroidal confinement systems and improvement of the predictive capability of burning plasmas in ITER, the impact of magnetic shear has been extensively investigated in the Large Helical Device (LHD) for comparison with tokamaks. Consequently, it was heuristically documented that the pronounced effect of magnetic shear, which has been hitherto considered to be ubiquitous and strongly impacts the core transport in the tokamak experiments, is not quite obvious. Namely, the kinetic profiles respond little under extensive modification of the magnetic shear in the core, although the local transport analysis indicates the sign of improvement in confinement transiently when the magnetic shear is reduced. It was thereby concluded that the magnetic shear in the core strongly influences the MHD activity, but it may only be one of the necessary conditions for the transport reduction, and some other crucial knobs, such as the density gradient or T_e/T_i ratio, would have to be simultaneously controlled. The low wavenumber turbulence seems to be suppressed under the weak shear, and the turbulent fluctuation intensity behaves in a consistent manner as a whole, following the conventional paradigm accumulated in the negative shear experiments in tokamaks. However, vigorous dynamics of turbulent fluctuations have occasionally been observed under the magnetic shear modification, which respond in much faster time scale than the characteristic time scale for either the magnetic diffusion or the profile evolution."}, title = {Impact of Magnetic Shear Modification on Confinement and Turbulent Fluctuations in LHD Plasmas}, year = {2008} }