Fabrication of 1 T Bi-2223 Superconducting Magnet with 92 mm Bore Diameter at 77 K

A Bi-2223 superconducting magnet for practical use in liquid nitrogen is designed and fabricated. Bi-2223 tapes prepared by ConTrolled Over Pressure (CT-OP) process are used for the winding, and the critical current at 77.3 K and self-field is in the range of 174–185 A. 28 double-pancake coils are resistively connected in series by copper terminals. High critical current tape is used for top and bottom double-pancake coils, since the magnetic field normal to the tape surface is highest at the top and bottom of the magnet. Two iron plates at top and bottom of the magnet are used for reduction of the normal component of magnetic field to the Bi-2223 tape, since the total performance of the magnet is determined by the minimum critical current at maximum normal magnetic field component to the tape. The inner bore diameter of the magnet is 92 mm. And the homogeneity of magnetic field of long-axis direction in 50 mmφ × 100 mm length is within 3%. The maximum magnetic field at the center of the bore is over 1.0 ...