30D17P
PANTA における分光による揺動スペクトル観測
Observation of turbulent fluctuation of light emissions in PANTA
大坪聡 1, 藤澤彰英 2,3, 永島芳彦 2,3, 柿川伸介 1, 稲垣滋 2,3,小林達哉 1, 山下哲生 1, 山田宗太郎 1, 藤野博充 1, 大野翔 1, 糟谷直宏 2,3, 佐々木真 2,3, 伊藤早苗 2,3 , 伊藤公孝 3,4Satoru Ohtsubo1, Akihide Fujisawa2,3, Yoshihiko Nagashima2,3, Shinsuke Kakigawa1, Shigeru
Inagaki2,3, Tatsuya Kobayashi1, Tetsuo Yamashita1, Soutaro Yamada1, Hiromitsu Fujino1, Syou Ohno1,Naohiro Kasuya2,3, Makoto Sasaki2,3, Sanae-I. Itoh2,3 and Kimitaka Itoh3,4
1 九州大学総合理工学府 2 九州大学応用力学研究所
3 伊藤極限プラズマ研究連携センター 4 核融合科学研究所
1 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University
2 Research Institute for Applied Mechanics, Kyushu University
3 Itoh Research Center for Plasma Turbulence, Kyushu University
4 National Institute for Fusion Science
Turbulence plays an important role on
structure formation of magnetically confinedplasmas. Thus the understanding of plasma
turbulence is strongly required for realizationof fusion reactors. In PANTA in Kyushu
University [1], a spectroscopic system is being
made to aim at two-dimensional measurementof turbulence, and the system will be extended
for tomographic reconstruction of turbulence
images. This poster presents initial results froma test of the system on spectral analysis of theline-integrated light emission, and future
experimental plans.
PANTA is a cylindrical linear plasma device
with the diameter of ~0.1 m and axial length of
4 m. Plasma is generated by helicon wave (7MHz, 3 kW). The magnetic field is fixed at
0.09 T in the present experiment.
The spectroscopic system consists of 132 (33rows x 4 columns) channels and can measuredifferent lights in wavelength using four kindsof optical filters ; infrared (900±20 nm), red(696.5±30 nm), blue (476.5±30 nm), and UV(294±20 nm). The 33 channels in a set arealigned in the vertical direction with theintervals of 5 mm. The filtered light signals,
integrated along the horizontal line-of-sightacross the plasma, are transferred tophoto-diode detectors through optical fibers.
The present measurement is performed forselected 16 channels for obtaining radial
profiles of fluctuations. The significant
fluctuation signals in blue light are obtained forargon plasmas, and for red light in a neon
plasma. Fast Fourier Transform (FFT) wasapplied to the observed signals to obtain

fluctuation spectra with the frequency
resolution of ~50 Hz. Figure 1 (a) and (b)shows an examples of power spectra ofemission intensity fluctuations along the central
chord (including r = 0 mm) and deviated chordfrom the center (including r = 20 mm) in theblue light (ArII) in an argon plasma,
respectively. As is shown in Fig. 1, we can findseveral spectral peaks in low frequencies, forexample at ~5 kHz, significantly above thenoise level, suggesting a possibility to infer theradial position where such coherent modes arelocated.

Fig.1. Bold lines of (a) and (b) indicate power spectra ofemission intensity (blue) along the central line-of-sight(including r = 0 mm) and deviated line from the center(including r = 20 mm) in argon plasma, respectively.
Thin lines indicates noise level.

This work is supported by a grant-in-aid forscientific research from JSPS(23246162,21224014, 23360414, 23360409) and by thecollaboration
programsofNIFS(NIFS10KOAP023) and of the RIAM ofKyushu University.
References[1] H Arakawa et al Plasma Phys. Control.
Fusion 53 115009(2011)