Comparison of the Shielding Properties of Superconducting and Superconducting/Ferromagnetic Bi- and Multi-layer Systems

This paper compares the shielding properties of superconducting (SC) and superimposed superconducting/ferromagnetic (SC/FM) systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. Both bilayer structures, with the SC cup placed inside the FM one, and multilayer structures, made up of two SC and two FM alternating cups, have been considered. Induction magnetic field values have been calculated by means of a finite element model based on the vector potential formulation, simultaneously taking into account the non-linear properties of both the SC and FM materials. The analysis highlights that at low applied fields, the presence of a height difference between the edges of the SC/FM cups, as well as a suitable choice of the lateral gap between the cups, is a key factor in obtaining hybrid structures with a shielding potential comparable to, or even higher than, that of the single SC cup. In contrast, at high applied fields, all the hybrid arrangements investigated always provide much greater shielding factors than the SC cup alone. The computation results show that at both low and high applied fields, the multilayer solutions are the hybrid shields with the highest efficiency.