22P111-P
Electron Temperature and Density Measurements by Using Thomson Scattering
System in GAMMA 10
GAMMA 10 における Thomson 散乱計測システムを用いた
電子温度・電子密度計測
Masato Morimoto 1, Masayuki Yshikawa1, Yoriko Shima1, Junko Kohagura1, Mizuki Sakamoto 1,
Yosuke Nakashima1, Makoto Ichimura1, Tsuyoshi Imai1, Kazuo Kawahata2, Ichihiro Yamada2,
Ryo Yasuhara2, Hisamichi Funaba2, Takashi Minami3, Yoshiaki Miyata4
森本真人１, 吉川正志 1, 嶋頼子 1, 小波蔵純子 1, 坂本瑞樹 1,中嶋洋輔 1, 市村真 1, 今井剛 1, 川端一男 2, 山田一博 2,安原亮 2, 舟場 久芳 2, 南貴司 3, 宮田良明 4
1Plasma Research center, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577, Japan
2
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-city, Gifu 509-5292, Japan
3
Institute of Advanced Energy, Kyoto University, Gokasho, Uji-city, Kyoto 611-0011, Japan
4
Japan Atomic Energy Agency, Naka Fusion Institute, 801-1 Mukouyama, Naka, Ibaraki, 311-0193, Japan１
筑波大学プラズマ研究センター 〒305-8577 茨城県つくば市天王台 1-1-1
２
核融合科学研究所 〒509-5292 岐阜県土岐市下石町 322-6
３京都大学エネルギー理工学研究所 〒611-0011 京都府宇治市五ケ庄
4
日本原子力開発機構 那珂核融合研究所 〒305-0193 那珂市向山 801-1
Electron temperature and density are important parameters to describe a state of plasma. In GAMMA 10, aYAG-Thomson scattering (YAG-TS) system was constructed in order to measure electron temperature
under National Institute for Fusion Science collaboration program. We can successfully measure theelectron temperatures shot-by-shot. We tried to estimate the electron density by comparing the results of TS
experiments and the Rayleigh scattering experiments. We can successfully obtain the electron temperatureand electron density by using the Thomson scattering system in GAMMA 10.

1. Introduction
Electron temperature and density are importantparameters to describe a state of plasma. TS
measurement is a highly reliable measurement ofelectron temperature and density in fusion devices
and in the GAMMA 10 device. GAMMA 10 is thetandem mirror device that confines plasmas withmagnetic mirrors and electrostatic potentials. In
GAMMA 10, plasma is produced and heated by ion
cyclotron radio frequency (ICRF) heating. In
addition the electron in the central cell is directly
heated by electron cyclotron resonance heating(ECRH).
In GAMMA 10, YAG-Thomson scattering(YAG-TS) system was introduced in 2009, and thefirst signal by the TS was obtained in 2010.
2. Thomson scattering
The TS is the elastic scattering phenomena by thefree electron when an electromagnetic wave isinjected. The incident electromagnetic wave isscattered and the wavelength of it is affected by
Doppler shift by the electron thermal motion. The
scattered spectrum has the Maxwell distribution andits half width of half maximum (HWHM) given byfollowing expression (1),(1)
Here, , c, ,,and
are the wavelengthof the incident electromagnetic wave, the velocityof light, the scattering angle, Boltzmann constant ,electron temperature, and the electron mass,respectively.
According to the equation (1), all quantities except
the electron temperature are given, and then theelectron temperature is estimated by measuring
HWHM of scattering spectrum.
In GAMMA10, we observed the scattering lightof 90 degrees. The side view of the TS system inGAMMA
10isshownin
Fig1.

system is accord with that obtained by microwave
interferometer. Then, we can successfully obtain theelectron temperature and density by using the TSsystem in GAMMA 10.
5. Summary
In GAMMA 10, we successfully measure theelectron temperature and density by using TSsystem. We obtained electron temperature about
50eV and electron density about
×1018m-3 during ICRF heating periods.

Fig. 1. The side view of the TS system in GAMMA

10.
3. Rayleigh scattering experiments
The Rayleigh scattering is the elastic scatteringwith atoms and molecules. In Rayleigh scatteringexperiment, we filled nitrogen gas in the GAMMA
10 vacuum vessel and reduced power of YAG-laser
is injected in. Then we measured the scattering light.
The Rayleigh scattering experiment is used for
adjusting the optical system and calibration of
optical sensitivity of total measuring system. It is
important for estimation of the plasma electron
density by the total measured photons in the TS
signals.
4. Electron temperature and density
measurement
In GAMMA 10, we can measure electron
temperature to 500 eV and the signal to noise ratio
is about 3 to 5. We can obtain electron temperature
about 50eV during ICRF heating periods. Withapplication of ECRH, electron temperature
increased to about 100eV.
The numbers of the photons in the scattering
phenomenon is given by the following equation (2),･ ・ ・ ・・(2)Here,, P, n, L, h, , ⊿ ,, andare thenumber of photons, the laser energy, the density, thescattering length, the Plank constant, the scatteringcross section, the solid angle, the transmission
efficiency, and the laser wavelength, respectively.
We obtained the electron density at the plasma
centerduring theICRF period. The electron density obtained by themicrowave interferometer is.
The electron density obtained by using the TS

References[1] M. Yoshikawa, et al., Plasma Fusion Res. 6, (2010)
1202095.
[2] K. Narihara, I. Yamada, H. Hayashi and K.
Yamaguchi, Rev. Sci. Instrum. 72, (2001) 1122.