Plasma and Fusion Research

Volume 21, 1405037 (2026)

Regular Articles

Engineering Perspective of the CFQS Quasi-Axisymmetric Stellarator and its Upgrade Status Toward the 1 Tesla Experiment

Hiroyuki TANOUE¹⁾, Sho NAKAGAWA¹⁾, Kazuki NAGAHARA¹⁾, Takanori MURASE¹⁾, Akihiro SHIMIZU^1,2), Hiroyuki YAMAGUCHI¹⁾, Kunihiro OGAWA^1,2), Hiromi TAKAHASHI^1,2), Mamoru SHOJI^1,2), Masaki OSAKABE^1,2), Shoichi OKAMURA¹⁾, Mitsutaka ISOBE^1,2,3), Yuhong XU⁴⁾, Haifeng LIU⁴⁾, Jun CHENG⁴⁾, Xiangqu WANG⁴⁾, Jie HUANG⁴⁾, Hai LIU⁴⁾, Xin ZHANG⁴⁾, Heng LAN⁴⁾, Dapeng YIN⁵⁾

1): National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
2): The Graduate University for Advanced Studies, SOKENDAI, Toki 509-5292, Japan
3): Department of Physics, Faculty of Science, Mahasarakham University, Mahasarakhum 44150, Thailand
4): Institute of Fusion Science, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, People’s Republic of China
5): Anhui Link Future Technology Co., LTD, Hefei 230000, People’s Republic of China

(Received 29 January 2026 / Accepted 22 April 2026 / Published 24 July 2026)

Abstract

The National Institute for Fusion Science in Japan and Southwest Jiatong University in China are proceeding with the CFQS quasi-axisymmetric stellarator project since 2017. CFQS principal physical properties are as follows: toroidal periodic number N_p = 2, aspect ratio A_p = 4, and major radius R₀ = 1 m. Sixteen modular coils are employed to produce the quasi-axisymmetric magnetic field configuration. Its upgrade from the 0.1 T operation as the CFQS-TEST, hereafter called CFQS-T to the 1 T operation as the CFQS is ongoing. In this report, the finalized engineering design, R&D, established essential component manufacturing, and assembly of the CFQS-T are described. Subsequently, the upgrade status toward the CFQS is given, focusing on the further improved design of a support structure that can withstand the complex and enormous electromagnetic forces acting on the modular coils at the 1 T operation. Iterative design and validation using the finite element method revealed a rational support structure with low-cost, good port accessibility, and manufacturability even under a packed configuration of the CFQS main body due to its low-aspect ratio. The engineering knowledge obtained through the CFQS project, particularly regarding the improved support structure design, would contribute to developing next-generation advanced stellarators.

Keywords

CFQS, CFQS-T, quasi-axisymmetric stellarator, modular coil, finite element method, engineering design

DOI: 10.1585/pfr.21.1405037

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