Application of flux trapping in hard superconductors to magnetic shielding and magnetic levitation

A thermally switched magnetic shield which can both shield against and trap magnetic fields is described. The shield, consisting of a Nb-Ti sheet, can tap stably fields of up to 0.3T, and shield against fields of up to 0.35 +- 0.05T, when in the superconducting state. It provides large attenuation of alternating magnetic fields in the presence of a steady trapped field. It is shown to significantly reduce the eddy current damping of the mechanical vibration of a superconducting sample in a magnetic field, by shielding nearby normal metal surfaces. A specific application to magnetic levitation of gravitational radiation antennae is discussed. (author)