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

RE-Ba-Cu-O (REBCO, RE = rare earth) symmetric tape round (STAR((R))) 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((R)) 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((R)) 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((R)) wires can be substantially reduced using fewer tape strands of high-performance advanced MOCVD tapes and that the superior bend performance of STAR((R)) wires can be maintained, even using 12 strands of advanced MOCVD tapes with 4 mu m thick REBCO films.

Automated summary

By using advanced MOCVD tapes, REBCO symmetric tape round (STAR((R))) wires with 1.5-2.5 mm diameter and 4-12 strands have been successfully fabricated. It has been demonstrated that 1.5 mm diameter wires made with just 4 advanced MOCVD tape strands can achieve the same critical current (I-c) as 2.5 mm diameter wires made with 12 commercial-grade tape strands. These results indicate that the cost of STAR((R)) wires can be reduced by using fewer high-performance advanced MOCVD tapes while maintaining superior bend performance.