Bi-2212 is the only cuprate superconductor that can be made in round wire with high critical current density Jc; however, to date, its use in superconducting magnets is restricted because gas bubbles form during heat treatment, causing wire expansion, leakage and superconducting filament dedensification that greatly reduces Jc in coil length
This year we have developed over pressure (OP) processing and have shown that the critical current for wires processed at 25 bar is more than five times higher than samples processed at 1 bar with closed ends, a geometry that mimics a coil-length wire. Our results demonstrate a wire-fabrication process for Bi-2212 round wire that avoids the long-length loss of Jc. This process has raised Jc to ~500 A/mm2 at 20 T, very attractive values for high field magnets, and about 5 times higher than Nb3Sn at 20 T.
The chart is from other work that shows the potential of Bi-2212
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