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

Abstract

We modelled 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 the so-called percolation depinning and flux creep models to describe the current density versus electric field in HTS tapes. We compared model results with experimental data obtained from a Bi-2223/Ag double pancake coil. The experimental residual magnetization due to Is in the Bi-2223/Ag coil can be effectively modelled assuming an equivalent loop length of approximately 9 mm for 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 I s. These results demonstrate the validity of our model for Is, which considers the effects of flux creep and smaller Is loops in the multi-filamentary Bi-2223/Ag tape.

Nature of the low magnetization decay on stacks of second generation superconducting tapes under crossed and rotating magnetic field experiments

“…Nevertheless, having in mind that the overall sum of profiles of current ( J i ) inside of a SC specimen of cross-section area Ω, is by definition equal to zero (in the absence of a transport current), two different scenarios can be envisaged for the stack of SC tapes, with only one being physically correct. On the one hand, coupling currents of the same order of magnitude than J c may appear through a conductive matrix 7 , 18 – 21 , then, the SC tapes or the filaments they are composed from behave as electrically interconnected elements satisfying the condition , where Ω stands for the overall cross-section area of the stack. Thus, under this ansatz, we have obtained that the stack of tapes acts as a single SC-bulk of relative dimensions h */ w (Fig.…”

Feasibility study for reduction of the screening current induced field in a 2G high temperature superconducting coil

“…In this paper, we present an effective solution for this problem for the current sweep cycle method using thermal energy input in a 2G HTS coil. It is known that the effect of the SCF is large at a small load factor, while it becomes smaller if the load factor is sufficiently high [12,13]. If the coil temperature is increased by the thermal energy input, the load factor on the same operating current will be increased, and the SCF can be reduced.…”