ENHANCEMENT OF MAGNETIC-FIELDS GENERATED BY HIGH-T(C) SUPERCONDUCTING COILS

Abstract

High-T(c) superconducting pancake coils wound by Ag-sheathed Bi-based tapes have been placed in between ring-shaped mu metal sheets. The central magnetic field B0 of a single coil was found to be enhanced by 60 % at liquid nitrogen temperature 77 K, and increased approximately 26 % for a four-coil stacked magnet. Critical currents of these coils were decreased. B0 was also increased when the magnet was wrapt by a mu metal sheet. This indicates that the well-designed high permeability materials can significantly enhance the magnetic fields generated by high-T(c) superconducting magnets.