Detection of smaller Jc region and damage in YBCO coated conductors by using permanent magnet method

Hattori, Kenichi; Saito, Atsushi; Takano, Y.; Suzuki, T.; Yamada, H.; Takayama, T.; Kamitani, Atsushi; Ohshima, Shigetoshi

doi:10.1016/j.physc.2011.05.117

Cited by 23 publications

(14 citation statements)

References 7 publications

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“…Recently, Hattori et al have proposed a contactless and a high-speed measuring methods of j C in an HTS film [8]. In the following, this is called a scanning permanent magnet method.…”

Section: Introductionmentioning

confidence: 99%

High-speed method for analyzing shielding current density in HTS with cracks: implementation of <i>H</i>-matrix method to GMRES

Takayama

Kamitani

Saitoh

2016

JASSE

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Abstract. A high-speed analysis of a shielding current density in a high-temperature superconducting film containing cracks has been proposed. To this end, a numerical code has been developed for analyzing the shielding current density in an HTS film. In the code, the GMRES(k) with the H-matrix method has been implemented to solve a linear-system obtained by discretizing an initial-boundary-value problem of a nonlinear integro-differential equation with respect to time and space. The results of the computations show that, if the Jacobi scaling is not applied to the linear-system, the Newton method does not converge at a certain time step. Therefore, the Jacobi scaling is an necessary tool for analyzing the shielding current density. Furthermore, by using the GMRES(k) method with the H-matrix method as a linear-system solver, the time evolution of the shielding current can be analyzed with high speed. In conclusion, the speed of the GMRES(k) with H-matrix method is about 221.3 times as fast as that of the LU decomposition.

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“…Recently, Hattori et al have proposed a contactless and a high-speed measuring methods of j C in an HTS film [8]. In the following, this is called a scanning permanent magnet method.…”

Section: Introductionmentioning

confidence: 99%

High-speed method for analyzing shielding current density in HTS with cracks: implementation of <i>H</i>-matrix method to GMRES

Takayama

Kamitani

Saitoh

2016

JASSE

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“…Since physical properties of HTS films are remarkably degraded by cracks, crack detection is essential in a production process of largesized HTS films. For this reason, two types of contactless and nondestructive methods have been applied to crack detection: permanent-magnet method [1]- [3] and inductive method [4]- [6]. Although both of them are originally powerful methods for measuring the critical current density j C in HTS films, they are extremely time-consuming.…”

Section: Introductionmentioning

confidence: 99%

“…Hattori et al [3] improved the permanent-magnet method to drastically shorten the measurement time. In the improved method, while a permanent magnet is moved along a film surface, an electromagnetic force acting on the film is measured.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Permanent Magnet Method: Applicability to Crack Detection in High-Temperature Superconducting Film

2015

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Applicability of the scanning permanent-magnet (SPM) method to crack detection in a high-temperature superconducting film is assessed by means of the numerical simulation. As a measure of crack detection, a defect parameter is defined by using the electromagnetic force acting on the film. After the defect parameter is calculated along various scanning lines, the sensitivity and the resolution are determined numerically. The results of computations show that both the sensitivity and the resolution are hardly affected by the scanning speed. On the other hand, the resolution of the SPM method is much inferior to that of the inductive method. In this sense, the SPM method is a high-speed but low-resolution method for detecting cracks.

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“…This is mainly because F M must be determined at each measurement point. For the purpose of resolving this problem, Hattori et al [5] improved the permanent-magnet method. In the improved method, the magnet is moved along the film surface and, simultaneously, the electromagnetic force F z acting on the film is measured.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigations on Crack Identification in High-Temperature Superconducting Film

Kamitani

Takayama

Ikuno

et al. 2014

Plasma and Fusion Research

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The applicability of the scanning permanent-magnet method (SPM) to the crack identification in a hightemperature superconducting (HTS) film is investigated numerically. To this end, a defect parameter is defined for characterizing a crack position and it is calculated along various scanning lines. The results of computations show that a crack position can be roughly identified by scanning an HTS film in two opposite directions. Hence, the SPM must be combined with the inductive method to develop a fast high-resolution method for identifying a crack.

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Detection of smaller Jc region and damage in YBCO coated conductors by using permanent magnet method

Cited by 23 publications

References 7 publications

High-speed method for analyzing shielding current density in HTS with cracks: implementation of <i>H</i>-matrix method to GMRES

High-speed method for analyzing shielding current density in HTS with cracks: implementation of <i>H</i>-matrix method to GMRES

Numerical Simulation of Permanent Magnet Method: Applicability to Crack Detection in High-Temperature Superconducting Film

Numerical Investigations on Crack Identification in High-Temperature Superconducting Film

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