Plasma and Fusion Research

Volume 11, 2402111 (2016)

Regular Articles

Observation of Electron Density Fluctuations by Using the O-Mode Microwave Imaging Reflectometry (O-MIR) in LHD
Yoshio NAGAYAMA1,2), Soichiro YAMAGUCHI3), Zongbing SHI4), Hayato TSUCHIYA1), Shigehiro HASHIMOTO1), Naoki ITO5), Min JIANG3), Daisuke KUWAHARA6) and Shoji SUGITO7)
1)
National Institute for Fusion Science, Toki 509-5292, Japan
2)
The Graduate University for Advanced Studies, Toki 509-5292, Japan
3)
Kansai University, Suita 564-8680, Japan
4)
Southwestern Institute of Physics, Chengdu 610041, China
5)
National Institute of Technology, Ube College, Ube 755-8555, Japan
6)
Tokyo University of Agriculture and Technology, Koganei 184-8588, Japan
7)
The Institute for Molecular Science, Okazaki 444-8585, Japan
(Received 30 November 2015 / Accepted 16 June 2016 / Published 16 September 2016)

Abstract

The O-mode microwave imaging reflectometry (O-MIR) has been developed. The frequency is 26 - 34 GHz, which corresponds to the cutoff electron density of 0.8 - 1.5 × 1019 m−3. Since the local wave of the newly developed horn antenna millimeter wave imaging device (HMID) is fed by coaxial cable, the optical system of O-MIR is significantly simplified. By using O-MIR, the edge electron density fluctuation in an H-mode plasma is observed in LHD. The spectrum in the wave number and the frequency (k - ω) space is obtained by using the two-point correlation analysis. In the H-mode plasma the fluctuation amplitude is higher and the k - ω spectrum has the feature of the drift wave.

Keywords

microwave, imaging, reflectometry, diagnostics, plasma, LHD, helical, electron density, fluctuation

DOI: 10.1585/pfr.11.2402111

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