The development of bi‐based high‐temperature superconductor and coil

Ag-sheathed Bi-2223 superconducting oxide conductors with a critical current density of 66,000 A/cm2 at 77 K and coils that have generated magnetic fields of approximately 1.5 Tesla at 4.2 K have been successfully developed. The conductors consist of piled-up bundles of four to six sheets of element tapes with transport currents of approximately 200 Amps. The core size limit (CSL) prevented the production of single conductors that had the capacity to transport a current as high as 200 Amps at 4.2 K. Until now, it was difficult to develop a conductor having both high critical current density and the capability of transporting a large amount of current simultaneously. The role of CSL in large scale applications of high temperature superconducting oxides is discussed.