Critical current improvement and resistance evaluation of superconducting joint between Bi2223 tapes

We improved the critical current (I c) of the superconducting joint between the Bi2223 tapes by introducing the two-step sintering process. The in-field transport I c of ~ 300 A at 4.2 K and 1 T under a 10−9 Ω criterion was successfully demonstrated. The I c improvement can probably be attributed to the enhancement of the intergrain critical current density for a Bi2223 intermediate layer. Ultra-low in-field joint resistance below 10−14 Ω at 4.2 K and 1 T was also demonstrated using current decay measurement. To our best knowledge, this study is the first to demonstrate a practical level of in-field transport I c and ultra-low in-field joint resistance for the superconducting joint between Bi2223 tapes. We believe that this superconducting joint technology will facilitate development of persistent current mode Bi2223 superconducting magnets.