Superconducting Nb sub 3 Sn joints by chemical vapour deposition

Nb sub 3 Sn is an A15 superconductor with high critical current density in high magnetic fields. The A15 intermetallics are brittle and difficult to manufacture in defect-free lengths for large superconducting coils. A chemical vapor deposition (CVD) technique was used to deposit Nb sub 3 Sn on to prespliced Nb sub 3 Sn substrates to form a superconducting joint between two superconductive sections. The CVD-deposited material was found to have a very fine grain structure together with a T sub c of between 16.2 and 17.8K in zero field. A critical current density of greater than 500 000 A cm exp -2 was obtained at 5 T. The CVD layer bridged the gap between two spliced superconductors. A CVD coating of 3.5 mu m per side increased the current capacity at 5 T from a baseline capacity of 66 A mm exp -1 on the original material to above 80 A mm exp -1 .