Effect of magnetic configuration on particle transport and density fluctuation in LHD

Kenji Tanaka, Clive Michael, Masayuki Yokoyama, Osamu Yamagishi, Kazuo Kawahata, Tokihiko Tokuzawa, Mamoru Shohji, Hiroshi Yamada, Jyunichi Miyazawa, Shigeru Morita, Katsumi Ida, Mikiro Yoshinuma, Kazumichi Narihara, Ichihiro Yamada, Shigeru Inagaki, Leonid Vyacheslavov, Andrei Sanin, Sadayoshi Murakami, Arimitsu Wakasa

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

The characteristics of particle transport in three different magnetic configurations are studied from density modulation experiments in the Large Helical Device (LHD). These three configurations are represented as different magnetic axis positions (Rax) of the vacuumfield. Experiments were carried out in a range of different heating powers for each configuration with almost constant density. The experimental values of particle diffusion coefficients (D) and particle convection velocities (V) are compared with neoclassical estimates. The value of D is found to be anomalously large compared to neoclassical values in both the core and edge in all configurations. At low collisionality, this anomaly tends downward. The core convection velocities are comparable with neoclassical estimates. In more-outward-shifted configurations, particle transport is enhanced. The electron temperature and electron temperature gradient are the determinate parameters for D and V, respectively, in each configuration. The effective helical ripple is one of the important parameters for particle transport in the LHD; however, other hidden parameters exist. The role of fluctuations in particle transport is investigated from turbulence measurements using a two-dimensional phase contrast interferometer. Three kinds of fluctuation having different locations, propagation direction, and peak wave number are observed. One of these, which exists in the outermost edge region and propagates in the ion diamagnetic direction in the laboratory frame, plays a possible role in edge anomalous diffusion. The amplitudes of ion diamagnetic fluctuation components are compared with the linear growth rate of the ion temperature gradient mode.

Original languageEnglish
Pages (from-to)97-111
Number of pages15
JournalFusion Science and Technology
Volume51
Issue number1
DOIs
Publication statusPublished - Jan 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering
  • Materials Science(all)
  • Mechanical Engineering

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