Turbulence Response in the High Ti Discharge of the LHD

A high ion temperature (Ti) was achieved using a combination of perpendicular and parallel injected neutral beams in the Large Helical Device (LHD). Microturbulence spatial profiles in a high-Ti discharge were measured by two-dimensional phase contrast imaging (2D-PCI) through almost the entire vert...

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Bibliographic Details
Published in:Plasma and Fusion Research 2010/12/10, Vol.5, pp.S2053-S2053
Main Authors: TANAKA, Kenji, MICHAEL, Clive, VYACHESLAVOV, Leonid, FUNABA, Hisamichi, YOKOYAMA, Masayuki, IDA, Katsumi, YOSHINUMA, Mikiro, NAGAOKA, Kenichi, MURAKAMI, Sadayoshi, WAKASA, Arimitsu, IDO, Takeshi, SHIMIZU, Akihiro, NISHIURA, Masaki, TAKEIRI, Yasuhiko, KANEKO, Osamu, TSUMORI, Katsuyoshi, IKEDA, Katsunori, OSAKABE, Masaki, KAWAHATA, Kazuo, Group, LHD Experiment
Format: Article
Language:English
Subjects:
ion temperature gradient mode
LHD
neoclassical transport
phase contrast imaging
turbulence
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Summary:A high ion temperature (Ti) was achieved using a combination of perpendicular and parallel injected neutral beams in the Large Helical Device (LHD). Microturbulence spatial profiles in a high-Ti discharge were measured by two-dimensional phase contrast imaging (2D-PCI) through almost the entire vertical central chord. The 2D-PCI microturbulence spectral ranges covered wavenumbers (k) of 0.1-1 mm−1 and frequencies (f) of 20-500 kHz. The ion thermal conductivity (χi) increased in the entire region with increasing Ti. However, the difference between the experimental and neoclassical values of χi became smaller at ρ < 0.5, where ρ is the normalized position, in the high-Ti phase. Increasing fluctuation was not observed at this location, suggesting improved ion energy transport in this region. On the other hand, at ρ > 0.5, χi deviated from the neoclassical value due to enhancement of the experimental χi and reduction in the neoclassical χi by a positive radial electric field. Increasing turbulence was observed at ρ = 0.6-0.8, with fluctuations likely propagated to the ion diamagnetic direction in the plasma frame, suggesting that the observed turbulence degrades the ion energy transport at this location in the high-Ti phase.
ISSN:1880-6821
1880-6821
DOI:10.1585/pfr.5.S2053