Plasma and Fusion Research

Volume 3, S1069 (2008)

Regular Articles

Particle Transport and Fluctuation Characteristics around the Neoclassically Optimized Configuration in LHD

Kenji TANAKA, Clive MICHAEL, Leonid N. VYACHESLAVOV¹⁾, Masayuki YOKOYAMA, Sadayoshi MURAKAMI²⁾, Arimitsu WAKASA³⁾, Hidenobu TAKENAGA⁴⁾, Katsunori MURAOKA⁵⁾, Kazuo KAWAHATA, Tokihiko TOKUZAWA, Tsuyoshi AKIYAMA, Katsumi IDA, Mikiro YOSHINUMA, Ichihiro YAMADA, Kazumichi NARIHARA, Hiroshi YAMADA and the LHD Experimental Group

National Institute for Fusion Science,322-6 Oroshi-cho, Toki 509-5292, Japan
1): Budker Institute of Nuclear Physics, 630090 Nobosibirsk, Russia
2): Department of Nuclear Engineering, Kyoto University, Kyoto 606-8501, Japan
3): Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
4): Japan Atomic Energy Agency, 801-1, Mukoyama, Naka 311-0193, Japan
5): School of Engineering, Chubu University, Kasugai 487-8501, Japan

(Received 9 December 2007 / Accepted 26 March 2008 / Published 1 August 2008)

Abstract

Density profiles in LHD were measured and particle transport coefficients were estimated from density modulation experiments in LHD. The dataset used in this article included a wide range of discharge conditions, e.g., for different heating powers, magnetic axes, and toroidal magnetic fields scanned to cover wide regions for neoclassical transport. The minimized neoclassical transport configuration in the dataset (R_ax = 3.5 m, B_t = 2.83 T) showed peaked density profiles, and its peaking factors increased gradually with decreasing collisionality. These results are similar to those observed in tokamaks. At some other configurations, peaking factors were reduced with decreasing collisionality and a larger contribution of neoclassical transport produced hollow density profiles. Comparison between neoclassically and experimentally estimated particle diffusivities showed different minimum conditions. This suggests that the condition for neoclassical optimization is not the same as that for anomalous optimization. A clear difference in spatial profiles of turbulence was observed between hollow and peaked density profiles. A major part of the fluctuations existed in the unstable region of the linear growth rate of the ion temperature gradient mode and trapped electron mode.

Keywords

density profile, peaking factor, density modulation experiment, neoclassical transport, anomalous transport, diffusion coefficient, convection velocity, phase contrast imaging, turbulence

DOI: 10.1585/pfr.3.S1069

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This paper may be cited as follows:

Kenji TANAKA, Clive MICHAEL, Leonid N. VYACHESLAVOV, Masayuki YOKOYAMA, Sadayoshi MURAKAMI, Arimitsu WAKASA, Hidenobu TAKENAGA, Katsunori MURAOKA, Kazuo KAWAHATA, Tokihiko TOKUZAWA, Tsuyoshi AKIYAMA, Katsumi IDA, Mikiro YOSHINUMA, Ichihiro YAMADA, Kazumichi NARIHARA, Hiroshi YAMADA and the LHD Experimental Group, Plasma Fusion Res. 3, S1069 (2008).