Numerical Investigations on Crack Identification in High-Temperature Superconducting Film

Abstract

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.

High-Speed Algorithm for Shielding Current Analysis in HTS Film with Cracks

“…where j C and E C denote the critical current density and the critical electric field, respectively, and N is a positive constant. Under the thin-plate approximation, there exists a scalar function T (x, t) such that j = (2/b)∇ × (T e z ) and its time evolution is governed by the following integrodifferential equation [1][2][3][4]:…”

“…After discretized with the implicit scheme and the finite element method (FEM), an initial-boundary-value problem of the shielding current density is transformed to a problem in which nonlinear algebraic equations have to be solved at each time step. Although this method can be also applied to the shielding current analysis in an HTS film containing cracks [3,4], it is extremely time-consuming. Such time consumption is caused by a linear term with a dense matrix in the nonlinear equations.…”