Tech Brief: Advanced silver sheathed 2212/Ag wire for high field magnets

First commercial High Temperature Superconductors (HTS) are all tape-shaped (widths > 10 times thickness) because achieving useful current densities required them to be processed into tape form, even though this also makes it more problematic to use them in many important coil types.

2212 (Bi₂Sr₂CaCu₂O₈) HTS oxide is the only option that can be processed such that useful current densities are attained in product wire forms similar to proven low temperature superconductors (LTS) while surpassing them in field generating and operating temperature capability. Required now are higher current density designs, and lower cost, longer length production to enable broad-based usage in many applications where HTS tape usage is problematic.

In Phase 1 we achieved a remarkable 1.8 – fold critical current density (Jc) increase by applying a simpler, more effective bundle process and high-quality precursor, to produce 2212/Ag wire with more uniform filaments, spacing, and webbing thickness.  The feasibility of further Jc increases by chemical means was also demonstrated, with samples combining both mechanisms exhibiting an ~2.3-fold higher Jc than standard 2212 wires. These results greatly improve commercial prospects for HTS and 2212 wire.

In Phase II, process technologies will be established for the low-cost, high volume production of 2212 round and rectangular wire with these novel multifilament architectures and chemistries, for a 2-fold advance in operating current density, while also enabling much lower cost, improved yield, long length manufacturability, and superior performance.

The development will be completed to establish optimal combinations of wire architecture, chemistry and reaction conditions, with current density, uniformity, and quality used as primary performance metrics. Production capability to complete each process step at the best mode conditions will then be developed and validated by producing and testing long wires. These advances will provide rapidly available, cost-effective 2212 wire product for applications that are not viable with today’s HTS conductor options.