Plasma and Fusion Research

Volume 13, 1402039 (2018)

Regular Articles

Determining the Closed Flux Surface in a Helical Plasma in TOKASTAR-2 with an Electrostatic Probe
Hiromasa ITOU, Takaaki FUJITA, Hideki ARIMOTO, Atsushi OKAMOTO, Kenji MURAOKA, Ryoichi SUGIOKA, Kohei YASUDA, Ryoma YOKOYAMA, Masato MINOURA and Takahiro YAMAUCHI
Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
(Received 20 September 2017 / Accepted 7 March 2018 / Published 22 May 2018)

Abstract

The electron temperature and density were measured with an electrostatic probe in a helical plasma in the TOKASTAR-2 device in order to determine the location and the shape of the last closed flux surface (LCFS). The electron density inside the calculated LCFS was found to be higher in a helical plasma than in a plasma without a helical field when the electron-cyclotron-resonance layer was located inside the LCFS. Although errors in the manufacturing and installation of coils have been a concern, this result indicates that the LCFS formed in this device does not differ greatly from the calculated LCFS.

Keywords

TOKASTAR, stellarator, flux surface, field-line tracing, electron orbit, triple-probe measurement

DOI: 10.1585/pfr.13.1402039

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