22P102-P
Fluctuations Observed by Microwave Imaging in LHD
LHDにおけるマイクロ波イメージングを用いた揺動観測
Yoshio Nagayama1, Daisuke Kuwahara2, Tomokazu Yoshinaga3, Yasuji Hamada1, Shunji Tsuji-Iio2,Yuichiro Kogi4, Atsushi Mase5, Hayato Tsuchiya1 and Soichiro Yamaguchi6
長山好夫1，桑原大介2，吉永智一3，濱田泰司1，飯尾俊二2，近木祐一郎4，間瀬 淳5，土屋隼人1，山口聡一朗61

National Institute for Fusion Science, 322-6, Oroshi, Toki 509-5292, JapanTokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-85502, Japan3
National Defense Academy of Japan, 1-10-20, Hashirimizu, Yokosuka 239-8686, Japan
4
Fukuoka Institute of Technology, 3-30-16, Wajirohigashi, Higashi-ku, Fukuoka 811-0295, Japan
5KASTEC, Kyushu University, 6-1, Kasugakoen, Kasuga 816-8580, Japan
6
Kansai University, 3-3-35 Yamate, Suita 564-8680, Japan2

1

核融合科学研究所 〒509-5292 土岐市下石町322-6
東京工業大学 原子炉工学研究所 〒152-8550 東京都目黒区大岡山2-12-1
3
防衛大学校応用科学群 〒239-8686 横須賀市走水1-10-20
4福岡工業大学工学部 〒811-0295 福岡市東区和白東3-30-15
九州大学産学連携センター 〒816-8580 春日市春日公園6-1
6
関西大学システム理工学部 〒564-8680 吹田市山手町3-3-35

2The Microwave Imaging Reflectometry (MIR) and the Electron Cyclotron Emission Imaging(ECEI) has been developed in order to observe the electron density fluctuations and theelectron temperature fluctuations, respectively. The edge harmonic oscillation (EHO) isobserved by using 2-D MIR. The 2-D microwave image of EHO is has a narrow structure along
the magnetic field line near the iota=1.5 surface.
While the magnetic plasma confinement ishighly affected by the turbulence andmicro-instabilities, diagnostics for turbulence
have not been well established. In this work, themicrowave imaging diagnostic systems (MIDS)

such as the Microwave Imaging Reflectometry(MIR) and the Electron Cyclotron Emission
Imaging (ECEI) has been developed in order toobserve the electron density and the electron
temperature fluctuations, respectively [1-4]. The

Fig.1 Microwave imaging diagnostic system (MIDS) in LHD.

measurement in the world.

plasma reflects the X-mode microwave of{() }1/ 21
ωR = ωce + ωce2 + 4ω 2pe2(1)where ωce and ωpe are the electron cyclotron
frequency and the plasma frequency, respectively.
As frequencies of illumination wave are fRF=60.4,61.8, 63, 64.6 GHz, the plasma image on 4 different
plasma layers can be detected by the 7×7
Horn-antenna Mixer Arrays (HMA) [1,2]. The
frequency of ECEI is between 97 and 105 GHz.
Fig. 1 shows a schematic view of MIDS in LHD.
The optics is designed by using a FDTD simulation as
the plane LO wave illuminates the HMA uniformly,
and each channel of the antenna array is focused to apoint of the object plasma [3]. MIR and ECEI use
almost the same components. Differences are thefrequency, the illumination wave and the phasedetector. MIDS uses many channels of imaging
detectors, frequency separators and IF amplifiers. InLHD, they are made of beam lead type electronics
parts (resistor, capacitor, inductor, diode, MMIC, etc.)
and thin Teflon printed circuit board (PCB) by using
the micro-strip-line technology.
In LHD, the edge harmonic oscillation (EHO) isoften observed. MIR and ECEI observe the EHO
simultaneously. EHO is a fluctuation in the edge
plasma, and it was observed in the VH mode
plasma in DIII-D when the ELM is absent. The
feature of EHO is the frequency spectrum ofequally separated higher harmonics. Fig.2 shows
the FFT spectrum of the amplitude of MIR, andECE of EHO in the case of standard LHD operation(Rax=3.6 m, Bax=2.75 T, ne0=2.5×1019 m-3). The
rainbow color code indicates the fluctuation
amplitude in the log scale. The fundamental
frequency is 3 kHz and 10 harmonics isobserved.
Figure 3 shows a typical example of 3-D MIR
image of EHO. RF1, RF2, RF3 and RF4 correspond
to R=4.56, 4.55, 4.54 and 4.525 m, respectively.
The EHO is localized near the iota=1.5 surface,where R=4.525 m. Since the channel separation is 2cm, the width of EHO may be 5 cm along the flux
surface. Looking at the time, the EHO begins in theouter region and proceeds to the inner region.
Thickness of EHO in the radial direction is 2 cm,
because it appears between RF1 and RF2. So, theEHO has a single narrow structure along a field line.
Moving narrow structure makes signal with manyharmonics.
In conclusion, the 3-D microwave imaging
diagnostic system has been developed in LHD.
The 2-D microwave image of EHO that is obtainedby MIR shows the EHO has a very narrow structure
along the field line. This is the first 3-D MIR

Fig.2

FFT spectrum of (a) the amplitude of MIR,and (b) ECE of the edge harmonic
oscillations (EHO) in LHD.

Fig.3

2 D MIR image of EHO shown in Fig.2.

Acknowledgments
The work is supported by KAKEN(No.21246140), NIFS (KEIN1111, ULPP008) andNINS Imaging Science Project (KNSI001).
References[1] T. Yoshinaga, et al., Rev. Sci. Instrum. 81 (2010)
10D915.
[2] D. Kuwahara, et al., J. Plasma Fusion Res. SERIES
8 (2009) 649.
[3] T. Yoshinaga, et al., Plasma Fusion Res. 5 (2010)030.
[4] Y. Nagayama, et al., J. Plasma Fusion Res. 87(2011) 359 (in Japanese).