MgB₂ cylindrical superconducting shielding for cryogenic measurement applications: a case study on DC current transformers

A method for designing cylindrical hollow superconducting shields for cryogenic measurement devices operating in background fields of 1 T is proposed. The shield design is based on MgB₂ composite, manufactured by the reactive Mg liquid infiltration process [1]. The MgB₂ composite allows low-cost shields with good mechanical resistance to be realized easily. The geometrical design is benchmarked by the experimental characterization at 4.2 K. A design case study for the shield of a cryogenic DC current transformer is reported. Design results show a shielding efficiency of 70% for both the axial and radial components, with prospective measurement accuracy up to 10 ppm on 100 kA