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Direct Measurement of Ion Temperature and Poloidal Rotation Velocity with Doppler Spectroscopy during Bifurcation in Tohoku University Heliac

Toshihiro OKU, Sumio KITAJIMA, Keiichi ISHII, Yu SATO, Jo TACHIBANA, Satoshi KOIKE, Kosuke SHIMIZU, Atsushi OKAMOTO, Hiromi TAKAHASHI¹⁾, Masakazu TAKAYAMA²⁾ and Shigeru INAGAKI³⁾

1)

Department of Quantum Science and Energy Engineering, Tohoku University, Sendai 980-8579, Japan

2)

National Institute for Fusion Science, Toki 509-5292, Japan

3)

Akita Prefectural University, Honjyo 015-0055, Japan

4)

Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan

(Received 20 November 2013 / Accepted 4 March 2014 / Published 7 May 2014)

Abstract

Electrode biasing experiments were carried out in the Tohoku University Heliac (TU-Heliac) to investigate the role of ion viscosity maxima in the L-H transition. To investigate the relation between ion viscosity and poloidal Mach number, the driving force of the poloidal rotation and poloidal rotation velocity must be normalized by the ion temperature T_i and ion pressure P_i. Doppler spectroscopy was used to directly measure the ion temperature and the poloidal rotation velocity. Therefore, the dependence of the ion temperature and poloidal rotation velocity on the electrode current was obtained. The relation between the normalized driving force of the poloidal rotation and the poloidal Mach number M_p was non-linear. Bifurcation phenomena in the poloidal rotation appeared at M_p ∼ −3. These results qualitatively agreed with the neoclassical theory.

Copyright (c) 2014 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

plasma, heliac, electrode biasing, poloidal rotation, ion viscosity, L-H transition, bifurcation

DOI: 10.1585/pfr.9.3402051

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This paper may be cited as follows:

Toshihiro OKU, Sumio KITAJIMA, Keiichi ISHII, Yu SATO, Jo TACHIBANA, Satoshi KOIKE, Kosuke SHIMIZU, Atsushi OKAMOTO, Hiromi TAKAHASHI, Masakazu TAKAYAMA and Shigeru INAGAKI, Plasma Fusion Res. 9, 3402051 (2014).