22P105-P
ECE Imaging diagnostics on LHD
LHDにおけるECEイメージング計測
Daisuke Kuwahara1, Shunji Tsuji-Iio1, Yoshio Nagayama2, Hayato Tsuchiya2, Tomokazu
Yoshinaga3, Soichiro Yamaguchi4, Yuichiro Kogi5 and Atsushi Mase6
桑原 大介1, 飯尾 俊二1，長山 好夫2，土屋 隼人2, 吉永 智一3,
山口 聡一朗4, 近木祐一郎5 , 間瀬 淳61) Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro 152-8550, Japan
2) National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
3) National Defense Academy of Japan, 1-10-20 Hashirimizu, Yokosuka-shi, Kanagawa, Japan
4) Kansai University, 3-3-35 Yamate-cho, Suita 564-8680, Japan
5) Fukuoka Institute of Technology, 3-30-1 Wajiro-Higashi, Fukuoka 811-0295, Japan
6) Kyushu University, 6-1 Kasuga Koen, Kasuga 816-8580, Japan
1) 東工大, 2) 核融合研, 3) 防衛大, 4) 関西大, 5) 福岡工大, 6) 九大Electron Cyclotron Emission Imaging (ECEI) has been developed to investigate 2-D/3-D structure oftemperature fluctuations in the Large Helical Device (LHD). ECEI is an advanced ECE diagnostic method.
Key devices are a detector array, optics, and a multi-frequency receiver array. The detector array consistsof a 1-D horn antenna array and a printed circuit board (PCB) with mixer diodes and MMICs. The ECE
images of the plasmas are obtained with a microwave optical system for the microwave imaging
reflectometry (MIR). A multi-frequency receiver array consists of a band-pass filter array made on a PCB.
At the presentation, the ECEI system and results will be reported.

1. Introduction
A combined system of MIR and the ECEI has
been developed in LHD [1-3]. Microwave imaging
diagnostics has potential to observe fluctuations ofthe electron density and the electron temperature
profiles in magnetically confined high temperatureplasmas. When the plasma density and temperatureare sufficiently high, the intensity of Electron
Cyclotron Emission (ECE) equals to a black bodyradiation in magnetically confined plasma. The
electron temperature profile can be determined bymeasuring intensity of each frequency of the ECE,
since the ECE frequency corresponds to the radialposition. By using a 1-D receiving antenna array,the 2-D ECE profile (radial and poloidal directions)can be obtained. The electron temperature isconsidered to be equal on the same magnetic flux
surface so that ECEI can be one of the mostpowerful diagnostics to investigate MHD
instabilities.
2. ECE Frequency
MIR and ECEI are equipped with the same
imaging optics and an imaging detector 1-D/2-D
detector array. MIR is an active imaging system,
whereas ECEI is a passive one. The frequencies ofMIR and ECEI are different. Examples of thefrequency profiles of MIR and ECEI are shown inFig. 1, in the LHD plasma with ne0=3×1019 m−3,

Fig.1 Profile of ECE and cutoff frequencies in theLHD plasma with ne0=3×1019 m-3 and Bax=2.75 T(Rax=3.6 m).

Bax=2.75 T and Rax=3.6 m. In this configuration, thesecond harmonic ECE of 96.5 – 104.5 GHz
corresponds to the observation range of 4.44 – 4.55
m of the major radius. Because ECE of which
frequency is higher than the X-mode cutoff isobservable, the ECE frequency should be higher
than the MIR frequency.
3. ECE Imaging System

Figure 2 shows a schematic diagram of ECEI
detection system. The ECE signals from plasma arefocused on Horn-antenna Mixer Array (HMA) withthe focusing optics. In HMA, each antenna element
receives both ECE signals and the local oscillation(LO) wave, and mixer unit generates IF signal. The
frequency spectrum of IF signal is detected by the
band-pass filter (BPF) bank detection system. The
frequencies of each BPF are separated by 1 GHz
between 2 GHz and 9 GHz. The designed
bandwidth of each BPF is 500 MHz. Fig.3 showsobservation area of this system, in the case of Bax =2.1 T, Rax = 3.6 m. Sights of poloidal directions are
determined by the imaging optics. On the otherhand, radial channels are determined byfrequencies.

Fig.2 ECEI Detection System. ECE signals are
down-converted in to 2 - 9 GHz IF signals by LO
wave and each HMA element. Frequency detector
measured spectrum of IF signals.

4. Result
A typical example of ECEI signals is shown in
Fig.4. Fig.4(a) indicates two ECE signals observedby different antenna channels, same frequency
channels. Fig.4 (b) shows ECE spectrum of the“pol_2ch, 104 GHz” signal. During 7.2 to 7.7
seconds, 2 kHz fluctuation is observed.
5. Summary
A system that combines the V-band (60 – 65GHz) MIR and the W-band (96.5 – 104.5 GHz)ECEI has been developed for the LHD. MIR andECEI employs common imaging optics. They also
adopt the HMA that has a wide frequency response
50 – 110 GHz. ECE with a frequency of more than
97 GHz is selected by using a 95 GHz local
oscillator and a 93 GHz high-pass plate. A 1.5–9.5
GHz eight-channel multi-frequency detector hasbeen developed for ECEI. The frequency of eachchannel is well separated. Initial results indicatethat this ECEI system appears to work.

Fig.3
Observing Area of ECE Imaging. Colorindicates field strength of Bax = 2.1 T, Rax = 3.6 m.
Observing area is determined by sight lines of eachantenna element and magnetic field.

Acknowledgments
The work is supported by Grant-in-Aid for
Scientific Research (Grant No.21246140), NIFS
(KEIN1111, ULPP008) and NINS Imaging Science
Project (KNSI001).
References[1]D. Kuwahara, et al.: Rev. Sci. Inst. 81 (2010) 10D919.
[2]T. Yoshinaga, et al. Plasma Fusion Res. 5 (2010) 030.
[3]Y. Nagayama, et al. J. Plasma Fusion Res. 87 (2011)
359 (in Japanese).
Fig.4
An example of ECE waveform and FFTanalysis. (a) Waveforms of same frequency anddifferent antenna channels (poloidal direction). (b)Spectrum of pol_2ch 104GHz.