Plasma and Fusion Research

Volume 14, 3401081 (2019)

Regular Articles

Intermittent Magnetic Fluctuations Associated with High-Temperature Bubbles in an ECR Plasma
Shinji YOSHIMURA, Kenichiro TERASAKA1) and Masayoshi Y. TANAKA1)
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi, Toki 509-5292, Japan
1)
Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan
(Received 10 January 2019 / Accepted 15 March 2019 / Published 25 April 2019)

Abstract

Magnetic probe measurement has been performed in a cylindrical electron cyclotron resonance plasma in which localized high temperature electron region, i.e. high-temperature bubble, has been generated intermittently. It is found that the high-temperature bubble is accompanied by a pulsed magnetic fluctuation perpendicular to the external magnetic field. Polarities of the magnetic fluctuation suggest that it should be induced by a transient upstream electric current. This hypothesis has been validated by a simultaneous increase of electron flux in the downstream direction. No enhancement of electron flux in the upstream direction has been observed even under the existence of the bubbles. The result suggests that the electron velocity distribution function in the bubble should be an asymmetric one, which gives rise to an effective upstream electric current.

Keywords

intermittency, high-temperature bubble, magnetic fluctuation, electron cyclotron resonance plasma, HYPER-I device

DOI: 10.1585/pfr.14.3401081

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