Diffusion model for the computation of current density distributions in composite superconductors

We propose a magnetic diffusion model for the computation of current density distributions in composite superconductors. The two-dimensional model is based on Maxwell's equations and a non-linear constitutive relation between the current density and the electric field. The resulting diffusion equation is solved using the finite element method. We present numerical results on the time evolution of the current density distribution and the surface electric field in monofilamentary superconducting tapes excited by slow current ramps. The results demonstrate that the diffusion model appropriately describes the critical state, the electric field due to the self-field effect, and current sharing in composite superconductors.