Plasma and Fusion Research

Volume 10, 1402007 (2015)

Regular Articles

Simultaneous Measurement of Plasma Pressure Anisotropy with a Double-Pass Thomson Scattering Diagnostic System on the TST-2

Junichi HIRATSUKA, Akira EJIRI, Makoto HASEGAWA¹⁾, Yoshihiko NAGASHIMA¹⁾, Keishun NAKAMURA, Yuichi TAKASE, Hiro TOGASHI, Hiroshi TOJO²⁾, Takashi YAMAGUCHI and TST-2 group

: The University of Tokyo, Kashiwa 277-8561, Japan
1): Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan
2): Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-shi, Ibaraki 311-0193, Japan

(Received 28 March 2014 / Accepted 3 October 2014 / Published 27 February 2015)

Abstract

We have developed a double-pass Thomson scattering diagnostic system for the TST-2 spherical tokamak device. By measuring the first- and second-pass scattering signals simultaneously, we obtained the two directional pressures and we measured the pressure anisotropy (i.e., the ratio of the pressures) with an error of 5% - 10% for moderate density (≈ 2 × 10¹⁹ m⁻³) plasmas. We observed 30% and 100% anisotropy at the center and edge of the Ohmic-heated plasmas, respectively. We propose a three-temperature Maxwellian model, in which the fitting is better than in the shifted-Maxwellian model. The estimated plasma current density was close to the averaged current density. The results suggest that the contribution of thermal electrons to a plasma current is large in Ohmic-heated plasmas.

Keywords

Thomson scattering, double-pass configuration, pressure anisotropy, current density measurement, TST-2

DOI: 10.1585/pfr.10.1402007

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This paper may be cited as follows:

Junichi HIRATSUKA, Akira EJIRI, Makoto HASEGAWA, Yoshihiko NAGASHIMA, Keishun NAKAMURA, Yuichi TAKASE, Hiro TOGASHI, Hiroshi TOJO, Takashi YAMAGUCHI and TST-2 group, Plasma Fusion Res. 10, 1402007 (2015).