Plasma and Fusion Research

Volume 7, 2405017 (2012)

Regular Articles

Numerical Investigation on Accuracy and Resolution of Contactless Methods for Measuring jC in High-Temperature Superconducting Film: Inductive Method and Permanent Magnet Method
Teruou TAKAYAMA, Atsushi KAMITANI, Ayumu SAITOH1) and Hiroaki NAKAMURA2)
Yamagata University, 4-3-16 Johnan, Yonezawa, Yamagata 992-8510, Japan
1)
Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280, Japan
2)
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
(Received 2 December 2011 / Accepted 2 February 2012 / Published 1 March 2012)

Abstract

The accuracy and the resolution of two types of the contactless methods for measuring the critical current density in a high-temperature superconducting (HTS) film have been investigated numerically. To this end, a numerical code has been developed for analyzing the shielding current density in the film with a crack. The results of computations show that the accuracy of two contactless methods is degraded remarkably due to the crack. Specifically, in the permanent magnet method, the maximum repulsive force acting on the film decreases when the magnet approaches near the crack. It is found that, even if the crack size is small, the maximum repulsive force decreases. This means that the crack can be detected. In the inductive method, although the threshold current decreases because of the crack, its value does not necessarily decrease for the case with a small crack size. In fact, the accuracy is not degraded when the inner radius of the coil contains the crack of the film. For this reason, we conclude that the smallest possible inner radius is preferable to detect the crack.

Keywords

contactless method, critical current density, crack detection, high-temperature superconductor, numerical simulation

DOI: 10.1585/pfr.7.2405017

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This paper may be cited as follows:

Teruou TAKAYAMA, Atsushi KAMITANI, Ayumu SAITOH and Hiroaki NAKAMURA, Plasma Fusion Res. 7, 2405017 (2012).