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

We modelled the screening currents (I_s) 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 I_sin the Bi-2223/Ag coil can be effectively modelled, assuming an equivalent loop length of approximately 9 mm for the I_sin 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 I_s. These results demonstrate the validity of our model for the I_s, which considers the effects of flux creep and smaller I_sloops in the multi-filamentary Bi-2223/Ag tape.