Zero-quantum superconducting magnetic shielding apparatus and method

The design of a new superconducting magnetic shield is described, together with a method for achieving a final state in which no magnetic flux quanta are trapped in the shield's central region. The magnetic shield consists basically of a specially designed superconducting cylindrical tube, equipped with electrical and magnetic devices to remove flux quanta trapped during cooldown. An electrical current is applied along the length of the tube to cause mutual annihilation of trapped vortices and antivortices in the tube's central region and thus to remove flux quanta transverse to the cylinder axis. A parallel applied magnetic field then moves an appropriate number of vortices and antivortices from tube-end reservoirs to opposite ends until no longitudinal flux quanta thread the tube. Typical dimensions, various materials requirements, and conditions for successful operation of the magnetic shielding apparatus are discussed.