22P114-P
Present status of the Nd:YAG Thomson scattering system development for timeevolution measurement of plasma profile on Heliotron J (3)Heliotron Jプラズマの分布時間発展計測のためのNd:YAG トムソン散乱計測装置開発の現状 (3)YASHIRO Hiroaki1, MINAMI Takashi2, ARAI Shohei1, KENMOCHI Naoki1, MIZUUCHI Tohru2,
TAKAHASHI Chihiro3, NAGASAKI Kazunobu2, SANO Fumimichi2, OKADA Hiroyuki2,
KOBAYASHI Shinji2, YAMAMOTO Satoshi2, NAKAMURA Yuji2, HANATANI Kiyoshi2,
OHSHIMA Shinsuke4, MUKAI Kiyofumi1, LEE Hyunyong1, ZANG Linge,1 KAGAWA Tasuku1,MIZUNO Koji1, MINAMI Takayuki1, WATADA Hiroto1, WADA Yoshinobu1,KONOSHIMA Shigeru2, KASAJIMA Keijun5, HARADA Tomotaka5, HISADA Akifumi5
八代浩彰1, 南貴司2, 荒井翔平1, 釼持尚輝1, 水内亨2, 高橋千尋3, 長崎百伸2,佐野史道2, 岡田浩之2, 小林進二2, 山本聡2, 中村祐司2, 花谷清2, 大島慎介4,向井清史1, H.Y.Lee1, L.Zang1, 香川輔1, 水野浩志1, 南貴之1, 和多田泰士1,和田善信1, 木島滋2, 笠嶋慶純5, 原田伴誉5, 久田祥史5
1

The Graduate School of Energy Science, Kyoto University, Gokasho, Uji-shi, Kyoto, 611-0011, Japan
京都大学大学院エネルギー科学研究科 〒611-0011 京都府宇治市五ヶ庄
2Institute of Advanced Energy, Kyoto University, Gokasho, Uji-shi, Kyoto, 611-0011, Japan京都大学エネルギー理工学研究所 〒611-0011 京都府宇治市五ヶ庄
3National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu, 509-5292, Japan
核融合科学研究所 〒509-5292 岐阜県土岐市下石町322-6
4Pioneering Research Unit for Next Generation, Kyoto University, Gokasho, Uji-shi, Kyoto, 611-0011, Japan
京都大学次世代開拓研究ユニット 〒611-0011 京都府宇治市五ヶ庄
5Kyoto University Faculty of Enginnering, Undergraduate School of Electrical and Electronic Engineering,Yoshidahonmachi, Sakyou-ku, Kyoto 606-8501
京都大学工学部電気電子工学科 〒606-8501 京都市左京区吉田本町

We are developing polychromators for a new high repetition rate Nd:YAG Thomson scattering
measurement system for Heliotron J. This Nd:YAG Thomson scattering system enables to measure time
evolution of electron temperature and electron density simultaneously at 25 spatial points by 25
polychromators. Polychromators, containing five interferrence filters and five avalanche photo diodes, areused as spectral analyzers of scattered light. In this study, we make the optimized design of thepolychromators, and make performance check of the polychromators.

1. Introduction
Measurement of electron temperature anddensity profiles of plasma is one of the important
issues in magnetically confined plasma research.
The popular methods of the multipoint Thomson
scattering measurements are TV Thomson method,
LIDAR Thomson method, and Nd:YAG Thomson
method. Among them, Nd:YAG Thomson method
is especially suitable for high-repetition operation.
Nd:YAG laser beams are injected into plasmaand scattered by collision with electrons. Scattered
lights show spectral broadening, from which theelectron temperature is estimated. Total amount ofscattered lights is a function of electron density.
In Heliotron J, plasma width along the laser

beam is 25 cm, discharge pulse length is 200 ms.
The Nd:YAG Thomson scattering system isdesigned to measure at 25 spatial points in the 10ms cycle. Expected electron temperature is 10 eV 10 keV, and density is greater than 0.5×1019 m-3.
To make reliable measurement, spectral analysisof the scattered lights is an important factor. The
purpose of this study is to design and constructspectral analyzer system that is optimized for theNd:YAG Thomson scattering system, and to makeperformance check of the analyzer. In this study,
polychromators are selected as a spectral analyzer.
2. Polychromator Design
One polychromator has five wavelengthchannels and one Reileigh calibration channel
with interference filters and avalanche photo
diodes (APDs). The basic idea of thepolychromator is shown in Fig.1. Interference
filter is an optical filter that transmits
particular spectral bands and reflects others.
By these filters, the scattered lights are divided
into five wavelength ranges. Then, the lightsignals are transformed into electric signals byAPDs and transmitted to data-analyzingsystem.

Filter1
APDFilter2
APD

Filter3
APD
Filter4

APD

Filter5
APD
Calibration channel

Fig.1 Basic idea of the polychromator
The combination of the transmission
wavelength range for the five interference
filters is optimized by a performance
simulation code, so that the errors intemperature and density evaluation become
minimal. The result is listed in Table 1.

Table 1. List of filter wavelength
Filter.1
700 - 845nm
Filter.2
845 - 960nm
Filter.3
960 - 1025nm
Filter.4
1025 - 1050nm
Filter.5
1050 - 1060nm

interference filter as a function of the electron
temperature is shown in Fig.2 a). The electron
density is assumed to be 3×1019 m-3, which is atypical value for Heliotron J plasma. At least twochannels have enough count number to measure theaccurate plasma profile between 10 eV and 10 keV.
The expected errors, caused by bremsstrahlung, forthe temperature and density are shown in Fig.2 b).
Both errors are below 3%.
3. Performance Test for Polychromator
In this section, the method to make performancecheck of the polychromator is described. The
equipment for this test consists of a light source, amonochromator, a light chopper, and a laser power
meter. The light source, Apex Illuminator, and themonochromator are manufactured by Newport Co.
Ltd. A test light of selected narrow bandwavelength is produced by them. Then, the light istransformed into a pulse signal by the chopper, andgoes into the polychromator. Changing thewavelength band of the monochromator, theintensity of the light is measured at the entrance ofthe polychromator and each interference filter
channel. The transmission curves obtained from thistest are used for the derivation of the electron
temperature and density from the scattered lightsignal.
4. Summary
The design of the polychromator for the Nd:YAG
Thomson scattering system in Heliotron J isreported. As a result of performance simulation, theoptimized design of the polychromator is decided.
To check the polychromator performance, test
equipment has been prepared. We will accomplish
performance test of polychromators soon, and theresult will be discussed in the presentation.
Acknowledgments
The authors are grateful to the Heliotron J team fortheir excellent arrangement of the experiments. This
work is supported by the Collaboration Program of
the Laboratory for Complex Energy Processes, IAE,
Kyoto University and the NIFS Collaborative
Research Program (NIFS10KUHL030,NIFS09KUHL028, NIFS10KUHL033).

Fig.2 a)Photon counts for each channelb) Fractional errors in the estimation of electron
temperature and density
Estimation of scattered photon count for eachReferences[1] H. Rohr et al.: Periodic multichannel Thomson
scattering in ASDEX (1987).
[2] I. Yamada et al.: J. Plasma Fusion Res. Vol.79 No.9(2000).
[3] T. Minami et al.: Rev. Sci. Instrum. Vol.81 issue 10(2010).