Describing and understanding the influence of the inhomogeneity of the applied field on the behaviour of an HTS magnetic screen

In this communication, we explore experimentally and numerically how the behaviour of a high-temperature superconducting (HTS) magnetic screen is influenced by the inhomogeneity of the applied field to which it is subjected. This HTS screen is either a 30 mm-diameter disc-shaped bulk or a combination of this bulk with closed-loop coated conductors. Two methods are followed to vary the inhomogeneity of the DC
applied field. First, a unique source coil is employed, with a variable distance between the screen and the coil. Such a study is performed (i) experimentally using a bespoke 3-axis cryogenic Hall probe at 77 K and (ii) numerically with a 2D axisymmetric finite element model solved with the H-ф formulation. Second, the magnetic screening properties obtained for different geometries of the source coil are compared numerically. Both methods lead to similar conclusions: HTS magnetic screens are more effective for strongly inhomogeneous fields, as they take advantage of the natural curvature of the flux lines.