Numerical simulation of inductive method for measuring critical current density: Dependence of accuracy on shape and configuration of coil

The inductive method for measuring the critical current density j(C) in a high-temperature superconductor (HTS) has been investigated numerically. In the method, a HTS sample is exposed to the inhomogeneous ac magnetic field which is generated by a small coil placed just above the sample. While applying an ac Current I(t) = I(0) sin 2 pi ft in the coil, the third-harmonic voltage V(3) sin(6 pi ft + theta(3)) induced in the coil is measured. In order to simulate the inductive method, I(0)-V(3) curves are numerically determined and j(C) is estimated from their characteristics. The results of computations show that, for a HTS bulk, the accuracy of the inductive method is not at all influenced by the cross-sectional shape of the coil. In addition, it is found that, for double-sided HTS films on an MgO substrate, the accuracy of the inductive method is strongly affected by the thickness of the substrate. (C) 2009 Elsevier B.V. All rights reserved.