Numerical Investigation on Accuracy of Defect Detection in HTS Film by Inductive Method

AbstractThe inductive method for measuring the critical current density in a high-temperature superconducting (HTS) film has been reproduced numerically. To this end, a numerical code has been developed for analyzing the time evolution of a shielding current density in the HTS film containing a crack. The results of computations show that the accuracy of the inductive method is degraded due to the crack or the film edge. This result means that the inductive method can be applied to the crack detection. However, the crack located near the film edge cannot be detected because the crack is treated the same as the film edge

Equivalent-Circuit Model for Axisymmetric High-Temperature Superconducting Film: Application to Contactless jC Measurement System and Pellet Injection System

A high-temperature superconducting (HTS) film is used for numerous engineering devices. The analysis of the shielding current density in the HTS is essential to develop the HTS devices. By using the equivalent-circuit model (ECM) [1] , the analysis of the shielding current density becomes equivalent to solving the initial-value problem of the 1st-order ordinary differential system

Current Distribution Optimization by Using Genetic-Algorithm Based On-Off Method: Application to Pellet Injection System

The current distribution in the electromagnet is optimized by using the genetic-algorithm based on-off method so as to maximize the acceleration performance of the Superconducting Linear Acceleration (SLA) system. In the SLA system, a pellet container is accelerated by the interaction between a shielding current density and an applied magnetic field. By using the equivalent-circuit model, the distribution of the shielding current density is approximated as a set of the multiple current loops. In contrast, the current distribution in the electromagnet is represented by means of the on-off method. As the method for optimizing the current distribution in the electromagnet, two types of genetic algorithms are adopted. The results of computations show that the pellet velocity for the optimized current distribution is 1.3 times as fast as that for the homogeneous current distribution

Numerical Investigation on Contactless Methods for Identifying Defects in High-Temperature Superconducting Film

A numerical method has been developed for analyzing the shielding current density in a high-temperature superconducting (HTS) film containing multiple cracks. By using the method, the inductive method and the scanning permanent magnet method for contactlessly measuring the critical current density has been successfully reproduced, and the identifiability of the multiple cracks in the HTS film has been investigated. The results of computations show that, when the cracks are separated from each other, the multiple cracks can be detected individually in the two types of the contactless method. On the other hand, if the crack is pretty close to the interface, the multiple cracks is considered as a single crack. However, the crack position can be detected collectively. Therefore, the contactless methods is useful method for detecting the multiple cracks in an HTS film

Numerical Investigations on Detectability of Crack by Contactless jC-Measurement Method

The inductive method for measuring the critical current density jC and detecting the crack 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 the inductive method is degraded remarkably due to the crack. Specifically, it is found that, if the orthographic projection of the coil overlaps with the crack, the value of measured jC decreases. This is mainly because the spatial distribution of the shielding current density becomes asymmetry. In conclusion, the crack size and position can be accurately detected by measuring the jC-distribution in the HTS film