The influence of an initial trapped field on the magnetic shielding performance of bulk high-temperature superconducting tubes

Abstract

peer reviewedType-II superconducting hollow cylinders can act as efficient passive magnetic shields. Unlike in ferromagnetic materials, the magnetic shielding mechanism in a superconductor occurs through persistent currents flowing on the macroscopic scale. When a superconducting tube is used to shield a sequence of magnetic fields with different orientations, magnetic shielding performance levels are likely to be degraded because of the superconducting currents that are trapped in the superconductor. In this chapter we study experimentally the magnetic shielding configurations where an external magnetic field is applied first along one direction and a second field is subsequently applied along another (perpendicular) direction. In particular, we focus on the effect of an axial trapped field on the transverse shielding performance and on the effect of a transverse trapped field on the axial or the transverse shielding performance. Finally, we show how the pristine state of the tube can be restored by an appropriate magnetic field sequence, i.e., without heating up the shield above its critical temperature Tc