Recent issues in fabrication of high-Tc magnets and long-length multifilament conductors

Abstract

Abstract After fabricating long lengths (30–100 m) of Ag-clad Bi-2223 tapes by the powder-in-tube process, we co-wound them into pancake-shaped coils by the “wind-and-react” approach. Test magnets were then fabricated by stacking and connecting the coils in series. We then characterized the magnets at the temperatures of liquid helium (4.2 K), liquid neon (27 K), pumped liquid nitrogen (64 K.), and liquid nitrogen (77 K) and in background fields of up to 12 T. A test magnet containing 10 pancake coils generated magnetic fields as high as 2.6 T at 4.2 K. Multifilament conductors of BSCCO-2212 and BSCCO-2223 have also been fabricated in this study. A BSCCO-2212 multifilament conductor was fabricated with both pure silver and dispersion-strengthened silver (Ag-Al 2 O 3 ) as the sheath materials. After final heat treatment, the yield strength of the Ag-Al 2 O 3 matrix was twice that of the pure Ag matrix. At 4.2 K, critical current density of the Ag-Al 2 O 3 multifilament conductor approached 5 × 10 4 A/cm 2 at zero applied field and >2 × 10 4 A/cm 2 at 12 T. This paper addresses certain issues concerning high- T c magnets and long-length multifilament conductors.