Superconducting joint between multi-filamentary Bi2Sr2Ca2Cu3O10+δ tapes based on incongruent melting for NMR and MRI applications

Abstract

Recently, we proposed a method of forming superconducting joints between high-temperature superconducting wires based on the incongruent melting of an intermedium, called crystalline joint by melted bulk. Using this technique with GdBa2Cu3O7−δ-coated conductors, a superconducting joint with a critical current of 7 A at 77 K was obtained. In the present study, a joint between multi-filamentary Bi2Sr2Ca2Cu3O10+δ (Bi2223) tapes was prepared without an intermedium, employing incongruent melting of Bi2223 filaments in the tapes. A superconducting joint was successfully fabricated, with critical currents of 12.2 A and 177 A at 77 K and 4.2 K, respectively. A Bi2223 coil terminated with the present joint method was operated in persistent current mode and showed an ultra-low field decay rate with a characteristic resistance of 10−12 Ω at 77 and 4.2 K.