Experimental and numerical investigation of screening currents induced in a Bi-2223/Ag double pancake coil for space applications

Abstract

We modelled the screening currents (Is) induced in high-temperature superconducting (HTS) coils to develop a method for the characterization and design of HTS magnets for space applications. The analysis made use of so-called percolation depinning and flux creep models to describe the current density versus the electric field in HTS tapes. We compared the model results with the experimental data obtained from a Bi-2223/Ag double pancake coil. The experimental residual magnetization due to the Is in the Bi-2223/Ag coil can be effectively modelled, assuming an equivalent loop length of approximately 9 mm for the Is in the coil. The values calculated from the method quantitatively agreed with the results for various experimental conditions. We also successfully modelled the hysteresis of the magnetization due to the Is. These results demonstrate the validity of our model for the Is, which considers the effects of flux creep and smaller Is loops in the multi-filamentary Bi-2223/Ag tape.