Experimental study of particle transport and density fluctuations in LHD

K. Tanaka, C. Michael, A. L. Sanin, L. N. Vyacheslavov, K. Kawahata, S. Murakami, A. Wakasa, S. Okajima, H. Yamada, M. Shoji, J. Miyazawa, S. Morita, T. Tokuzawa, T. Akiyama, M. Goto, K. Ida, M. Yoshinuma, I. Yamada, M. Yokoyama, S. MasuzakiT. Morisaki, R. Sakamoto, H. Funaba, S. Inagaki, M. Kobayashi, A. Komori

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Abstract

A variety of electron density (ne) profiles have been observed in the Large Helical Device (LHD). The density profiles change dramatically with heating power and toroidal magnetic field (Bt). The particle transport coefficients, i.e. diffusion coefficient (D) and convection velocity (V) are experimentally obtained in the standard configuration from density modulation experiments. The values of D and V are estimated separately in the core and edge. The diffusion coefficients are found to be a function of electron temperature (Te), and vary with Bt. Edge diffusion coefficients are proportional to. Non-zero V is observed, and it is found that the electron temperature gradient can drive particle convection, particularly in the core region. The convection velocity both in the core and edge reverses direction from inward to outward as the Te gradient increases. However, the toroidal magnetic field also significantly affects the value and direction of V. The density fluctuation profiles are measured by a two-dimensional phase contrast interferometer. It was found that fluctuations which are localized in the edge propagate towards the ion diamagnetic direction in the laboratory frame, while the phase velocity of fluctuations around mid-radius is close to the plasma poloidal Er × Bt rotation velocity. The fluctuation level becomes larger as particle flux becomes larger in the edge region.

Original languageEnglish
Pages (from-to)110-122
Number of pages13
JournalNuclear Fusion
Volume46
Issue number1
DOIs
Publication statusPublished - Jan 1 2006
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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    Tanaka, K., Michael, C., Sanin, A. L., Vyacheslavov, L. N., Kawahata, K., Murakami, S., Wakasa, A., Okajima, S., Yamada, H., Shoji, M., Miyazawa, J., Morita, S., Tokuzawa, T., Akiyama, T., Goto, M., Ida, K., Yoshinuma, M., Yamada, I., Yokoyama, M., ... Komori, A. (2006). Experimental study of particle transport and density fluctuations in LHD. Nuclear Fusion, 46(1), 110-122. https://doi.org/10.1088/0029-5515/46/1/013