[Table of Contents]

Plasma and Fusion Research

Volume 10, 1402091 (2015)

Regular Articles

Development of a New Far Infrared Laser Interferometer in Heliotron J and First Results
Yoshiaki OHTANI, Shinsuke OHSHIMA1), Nuttasart ASAVATHAVORNVANIT, Tsuyoshi AKIYAMA2), Takashi MINAMI1), Kenji TANAKA2), Kazunobu NAGASAKI1), Nan SHI3), Tohru MIZUUCHI1), Nikolai. B. MARUSHCHENKO4), Shinji KOBAYASHI1), Hiroyuki OKADA1), Shinnichiro KADO1), Satoshi YAMAMOTO1), Linge ZANG1), Gavin M. WEIR1), Naoki KENMOCHI, Shigeru KONOSHIMA1), Yuji NAKAMURA, Yuriy TURKIN4) and Fumimichi SANO1)
Graduate School of Energy Science, Kyoto University, Gokasho, Uji 611-0011, Japan
1)
Institute of Advanced Energy, Kyoto University, Gokasho, Uji 611-0011, Japan
2)
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
3)
Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031, P.R. China
4)
Max-Planck-Institute for Plasma Physics, Wendelsteinstraße 117491 Greifswald, German
(Received 9 February 2015 / Accepted 1 September 2015 / Published 28 December 2015)

Abstract

A new far infrared (FIR) laser interferometer with high time resolution has been developed in Heliotron J for measuring high performance plasmas. The FIR laser interferometer is a heterodyne-type Michelson interferometer with a 1 MHz intermediate frequency. The interferometer uses a super rotating grating and the viewing chord passes through an off-axis position. Refraction in high density plasma is estimated using the TRAVIS ray-tracing code. The results suggest that it is possible to extend the range of the interferometer up to 1.5×1020 m−3. The first line-averaged plasma density measurements using the FIR laser interferometer have been made in ECH and NBI heated plasmas. The relative change in the density profile shape is evaluated from the ratio of the line-averaged density obtained by the FIR laser and microwave interferometer with a different viewing chord. The difference in the measurements suggests that a more peaked density profile is formed in NBI plasma than in ECH + NBI plasma, which is in agreement with Nd:YAG Thomson scattering measurements.

Keywords

FIR interferometer, plasma diagnostics, electron density, helical device, Heliotron

DOI: 10.1585/pfr.10.1402091

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This paper may be cited as follows:

Yoshiaki OHTANI, Shinsuke OHSHIMA, Nuttasart ASAVATHAVORNVANIT, Tsuyoshi AKIYAMA, Takashi MINAMI, Kenji TANAKA, Kazunobu NAGASAKI, Nan SHI, Tohru MIZUUCHI, Nikolai. B. MARUSHCHENKO, Shinji KOBAYASHI, Hiroyuki OKADA, Shinnichiro KADO, Satoshi YAMAMOTO, Linge ZANG, Gavin M. WEIR, Naoki KENMOCHI, Shigeru KONOSHIMA, Yuji NAKAMURA, Yuriy TURKIN and Fumimichi SANO, Plasma Fusion Res. 10, 1402091 (2015).