Persistent current distribution on the superconducting shield of the cioffi magnet

The superconducting magnet attributed to Cioffi1 employs a shield of sheet superconductor. In this paper the shielding effect is considered in detail as due to the induced persistent current distribution on the shield. The current distribution on shields of appropriate geometries is evaluated from the electromagnetic boundary conditions. Examination of Cioffi's original shielding geometry reveals several spots of singularly high current density. Critical phenomena at these spots may account for irreversible breakdown of the shielding action. A class of novel magnet geometries is proposed where the current density on the shield is uniform. Magnets of these geometries should function reversibly up to the critical field of the shielding superconductor. © 1969.