Magnetic shielding for improvement of superconductor performance

The concept of magnetic shielding for the enhancement of superconductor critical currents is discussed. Magnetic environment used for conditioning the magnetic self-field around current-carrying superconductors may drastically enhance the total critical currents of superconductor leads, resonators and electromagnets and reduce ac losses in them. Various configurations of shielding are considered and the current and field distributions are calculated to study the geometry-dependent enhancement effect. However, for successful implementation of appropriate magnet/superconductor heterostructures some special requirements on magnetic materials should be met which are discussed. (orig.)