Determination of Pinning Parameters in Flux Creep-Flow Model for E-J characteristics of High Temperature Superconductors by using Differential Evolution

The pinning parameters such as strength of pinning force, temperature dependence of pinning force and so on using in flux creep-flow model to explain electric field vs current density (E-J) characteristics were determined by Differential Evolution (DE). DE is one of the methods in Evolutionary Computation (EC) to find an optimization of a problem. First, a model data of E-J characteristics in which the pinning parameters were given was prepared, and it was confirmed that DE can find the given pinning parameters from the model data. Then, DE and mesh method were used to determine the pinning parameters in experimental E-J characteristics of GdBa₂CuO_7-δ high temperature superconductor. In mesh method, the all combinations of pinning parameters with constant interval for each parameter are calculated, and best set of pinning parameters is selected. It was found that DE shows better performance than mesh method in terms of calculation time and accuracy for determining pinning parameters.