Effect of High Ion Temperature on the Polytropic Coefficient in the End Region of GAMMA 10/PDX

Kunpei NOJIRI; Mizuki SAKAMOTO; Naomichi EZUMI; Satoshi TOGO; Takaaki IIJIMA; Seowon JANG; Akihiro TERAKADO; Yosuke KINOSHITA; Toshiki HARA; Tomonori TAKIZUKA; Yuichi OGAWA; Yousuke NAKASHIMA

doi:10.1585/pfr.14.2401086

Regular Articles

Effect of High Ion Temperature on the Polytropic Coefficient in the End Region of GAMMA 10/PDX

Kunpei NOJIRI, Mizuki SAKAMOTO, Naomichi EZUMI, Satoshi TOGO, Takaaki IIJIMA, Seowon JANG, Akihiro TERAKADO, Yosuke KINOSHITA, Toshiki HARA, Tomonori TAKIZUKA, Yuichi OGAWA, Yousuke NAKASHIMA

Author information

Kunpei NOJIRI
Plasma Research Center, University of Tsukuba
Mizuki SAKAMOTO
Plasma Research Center, University of Tsukuba
Naomichi EZUMI
Plasma Research Center, University of Tsukuba
Satoshi TOGO
Plasma Research Center, University of Tsukuba
Takaaki IIJIMA
Plasma Research Center, University of Tsukuba
Seowon JANG
Plasma Research Center, University of Tsukuba
Akihiro TERAKADO
Plasma Research Center, University of Tsukuba
Yosuke KINOSHITA
Plasma Research Center, University of Tsukuba
Toshiki HARA
Plasma Research Center, University of Tsukuba
Tomonori TAKIZUKA
Graduate School of Engineering, Osaka University
Yuichi OGAWA
Graduate School of Frontier Sciences, University of Tokyo
Yousuke NAKASHIMA
Plasma Research Center, University of Tsukuba

Keywords: ion temperature, ion polytropic coefficient, sound speed, Langmuir probe, ion energy analyzer

JOURNAL FREE ACCESS

2019 Volume 14 Pages 2401086

DOI https://doi.org/10.1585/pfr.14.2401086

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Abstract

The effect of high ion temperature on the ion polytropic coefficient (γ) was experimentally investigated in the end region of the GAMMA 10/PDX tandem mirror. The ion temperature parallel to the magnetic field (T_i||) was varied using the ion cyclotron range of frequencies (ICRF) waves, which heat the plasma in the central cell, and by applying an additional gas puff in the central cell. Assuming the ion sound speed, γT_i||was evaluated by a Langmuir probe, and T_i||was evaluated in an ion energy analyzer. These parameters were combined to evaluate γ. The time evolutions of γT_i||obtained from the probe and T_i||obtained from the energy analyzer were similar. The plasma in the end region can be regarded as collisionless, but γ was lower with ICRF heating than without the heating. A high T_i||component was identified in the heated case. As mentioned in a previous numerical study [B. Lin et al., Phys. Plasmas 23, 083508 (2016)], it is experimentally suggested that γ can be reduced by the high T_i||component resulting from the ICRF heating.

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