Plasma and Fusion Research

Volume 18, 2405026 (2023)

Regular Articles

Investigation of the Magnetic Field Configuration for Magnetic Surface Measurements in the CFQS Quasi-Axisymmetric Stellarator
Mamoru SHOJI1,2), Akihiro SHIMIZU1,2), Shigeyoshi KINOSHITA1), Shoichi OKAMURA1), Yuhong XU3) and Haifeng LIU3)
1)
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki 509-5292, Japan
2)
The Graduate University for Advanced Studies (SOKENDAI), Shonan Village, Hayama 240-0913, Japan
3)
Institute for Fusion Science, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, China
(Received 8 January 2023 / Accepted 7 March 2023 / Published 5 April 2023)

Abstract

It has been found that magnetic surfaces in the CFQS quasi-axisymmetric stellarator in a standard magnetic configuration are robust against error fields caused by misalignments of the modular coils. While this property is advantageous for preserving the magnetic field line structures for the plasma confinement as designed, it prevents the detection of the misalignments of the coils by magnetic surface measurements. Thus, a magnetic configuration specialized in measuring magnetic surfaces to detect the error fields is proposed. Calculations by tracing magnetic field lines reveal that the magnetic surfaces in the specialized magnetic configuration are sensitive to the error fields compared to those in the standard magnetic configuration. Additionally, the calculations demonstrate that a weighted electric current on some modular coils can make the magnetic surfaces more sensitive to the error fields, which enables the magnetic surface measurements to detect smaller misalignments of the modular coils in the CFQS.

Keywords

magnetic surface, magnetic field line mapping, magnetic island, error field, CFQS

DOI: 10.1585/pfr.18.2405026

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