High critical current STAR^® wires with REBCO tapes by advanced MOCVD

Abstract RE–Ba–Cu–O (REBCO, RE = rare earth) symmetric tape round (STAR®) wires of 1.5–2.5 mm diameter have been fabricated with 4–12 strands of symmetric REBCO tape made by advanced metal organic chemical vapor deposition (MOCVD). 1.5 mm diameter STAR® wires made with just four advanced MOCVD tape strands are able to sustain nearly the same critical current (I c) as 2.5 mm diameter wires made with 12 commercial-grade tape strands. An I c of 1070 A, corresponding to an engineering current density (J e) of 597 A mm−2, has been demonstrated at 4.2 K, 30 T in 1.5 mm diameter, four-strand wire at a bend radius of 15 mm. This I c value exactly matches the I c expected from the lift factor of the tape strands used in the wire. The 2.5 mm diameter STAR® wires made with 12 advanced MOCVD tape strands exhibit an I c of 1075 A at 77 K, self-field and sustained currents of 2500–2750 A at 4.2 K, 30 T before burnout, corresponding to a J e greater than 500 A mm−2. These results show that the cost of STAR® wires can be substantially reduced using fewer tape strands of high-performance advanced MOCVD tapes and that the superior bend performance of STAR® wires can be maintained, even using 12 strands of advanced MOCVD tapes with 4 μm thick REBCO films.