Nonlinear magnetic diffusion in a Bi2212 hollow cylinder: Measurements and numerical simulations

This paper compares numerical simulations and measurements of the nonlinear magnetic diffusion phenomenon in a Bi2212 high temperature superconducting (HTS) hollow cylinder. Although the measurements were done many years ago, it is only recently that computer power has become sufficient to reproduce the experiment by simulation on a personal computer in a reasonable time. Observations of flux density (magnitude and phase) both inside and outside the cylinder were carried out at different frequencies and magnitudes of a sinusoidal applied field. In addition, the computed current and flux density profiles inside the superconductor were obtained. The superconductor was modeled by E - J characteristics that depend on J(c) and a power law exponent n. Both parameters are isotropic functions of B. The paper shows that numerical methods are useful to extract model parameters and to predict the behavior of HTS elements entering in the conception of real applications, such as the inductive fault current limiters.