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Observation of Sheet Structure During Coaxial Helicity Injection in the QUEST Spherical Tokamak

Yuya OTSUKA¹⁾, Takumi ONCHI¹⁾, Kengoh KURODA²⁾, Roger RAMAN³⁾, Ryuya IKEZOE¹⁾, Takuto MOTOKI¹⁾, Makoto HASEGAWA¹⁾, Toshiki KINOSHITA¹⁾, Hiroshi IDEI¹⁾, Takeshi IDO¹⁾, Kazuaki HANADA¹⁾

1)

Kyushu University, Kasuga 816-8580, Japan

2)

Japan Coast Guard Academy, Kure 737-8512, Japan

3)

University of Washington, Washington 98195, USA

(Received 22 April 2025 / Accepted 5 July 2025 / Published 10 September 2025)

Abstract

A sheet structure has been observed in a coaxial helicity injection experiment conducted on the spherical tokamak QUEST. After a bubble burst, a high-speed visible camera captured a formation of the sheet in the region between the main plasma and the ring electrode. Subsequently, the sheet faded out, resulting in the formation of closed flux surfaces.

Copyright (c) 2025 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

spherical tokamak, coaxial helicity injection, magnetic measurement, high-speed camera, magnetic reconnection, QUEST

DOI: 10.1585/pfr.20.1202045

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References

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