A Simple Measurement Technique for Critical Current Density by Using a Permanent Magnet

Plasma and Fusion Research

Itoh

et al. 2011

Possibility of the accuracy improvement in the permanent magnet method for measuring the critical current density of a high-temperature superconducting (HTS) thin film has been investigated numerically. To this end, a numerical code has been developed for analyzing the shielding current density in an HTS sample. By using the code, the permanent magnet method has been reproduced numerically. The results of computations show that, by using the magnet strength B F as large as possible, the high accuracy can be assured with little effort. Furthermore, in order to improve the measurement accuracy of the critical current density near the film edge, it is necessary to use the magnet with the smallest radius.

Section: Numerical Resultsmentioning

confidence: 99%

“…As a novel noncontact method for measuring j C , Ohshima et al proposed the permanent magnet method for measuring the critical current density j C in a HTS thin film [2,3]. While moving a permanent magnet placed above an HTS thin film, they measure an electromagnetic force acting on the film.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on Accuracy Improvement of Permanent Magnet Method for Measuring jC in High-Temperature Superconducting Film

Plasma and Fusion Research

Itoh

et al. 2011

“…In this section, we evaluate the performance of the virtual voltage method by means of the code. To this end, the numerical simulation of the permanent magnet (PM) method [8,9] is performed by means of the code.…”

Section: Numerical Experimentsmentioning

confidence: 99%

Numerical Method for Analyzing Shielding Current Density in HTS Film with Multiple-Layer/Multiply-Connected Structure

Plasma and Fusion Research

Ikuno

et al. 2013

The governing equations of the shielding current density j in a high-temperature superconducting film are formulated for the case where the film contains cracks or holes. Since the derived equations cannot be solved only with the boundary condition j · n = 0 on the film surface, additional conditions are also derived. A numerical method is proposed for solving the initial-boundary-value problem of the equations and its performance is evaluated by means of the numerical simulation of the permanent magnet method.

“…Ohshima et al proposed another contactless method for measuring j C [4,5]. In the method, while moving a permanent magnet above an HTS film, the electromagnetic force acting on the film is measured.…”

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

Saitoh

2016

JASSE

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.