Magnetic Shield Using a Bi-2223 High-Temperature Super- conductor

Katsumi Ohata* Junichi Sato* ABSTRACT: Magnetic shielding for strong magnets using a high-temperature superconductor that can be operated at liquid nitrogen temperature has been studied. Long and large-cross-section (9 mm wide and 0.5 mm thick) 54-filament Bi-2223/Ag tape was developed. Double pancake coils were wound using the tapes having sufficient bending strain tolerance for the react-and-wind process. An active shield with a clear bore of 524 mm, an outer diameter of 596 mm, and a height of 480 mm was assembled by stacking the double pancake coils. Calculation of leakage field revealed that effective shielding is possible by the axial distribution of operating current. Shielding properties were evaluated for the magnetic field leaked from a NbTi superconducting magnet system. The leakage field was 10 -2 T without shielding, and shielding reduced it to 5×10 T. These results show that the high-temperature superconducting magnetic shielding is promising.