Magnetic diffusion and dissipation in high-Tc superconductors subjected to sinusoidal applied fields

Solution of the linear magnetic diffusion equation of a superconductor slab with a sinusoidal applied field is used to explain recently reported experimental results on the transient response of a high-T-c superconductor tube. The developed linear model can qualitatively explain very well the experimentally observed delay between the applied field and the penetrated field, and other salient features of the experiments. The analysis shows that the linear magnetic-flux-density profile of Bean's critical-state model is not approached, even under quasi-steady-state conditions. A direct consequence of magnetic diffusion is that, under AC steady-state condition, dissipation is always associated with rhoJ(2), in addition to the hysterestic loss. The results of the analysis can also be used to explain qualitatively the characteristics of a superconductor-shielded core reactor. The effects of nonlinear magnetic diffusion and heating are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.