Development of long length Bi-based/Ag tapes and experimental magnets

Abstract

Long lengths of multifilamentary superconducting (BiPb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ (Bi-2223)/Ag tapes up to 250 m made with "powder-in-tube" (PIT) process have been successfully prepared on a laboratory scale. Reproducible critical current density of between 12,000-18,000 A/cm/sup 2/ in the long length tapes have been achieved using the optimal reduction in flat-rolling procedure and standard flat-rolling method as the intermediate deformation between sintering periods. Several coils have been fabricated from sections of the long length tape, using the co-wound react-and-wind (R&W) procedure for double pancake-shaped coils and wind-and-react (W&R) procedure for solenoidal pancake shaped coils. Each coil was fabricated by co-wounding three tapes on 30 mm-diameter mandrel. An experimental magnet was designed and constructed by stacking together coils. Dimensions and parameters of this magnet are as follows: height, 105 mm; winding ID, 32 mm; OD, 120 mm; total number of turns, 1068. Total conductor length in the magnet was /spl sim/870 m. The coils were connected in series and then tested at 77 K. The field constant at mid-plane of the magnet, determined by introducing a Hall probe in the bore of the magnet, was /spl sim/105 Gs/A and it generated 0.24 T magnetic field at 77 K. A detailed investigation of the J/sub c/-B properties and J/sub c/-strain characteristic of the Bi-2223 tapes as designing parameters and properties of the test magnet have been carried out.