Continuous Wire Extrusion Enables Improved Performance of Nb3Sn Superconductor

Improvements to the superconducting magnets used in high energy physics experiments will depend on increasing the critical current density and stability of Nb3Sn superconductor wire. Major improvements in the performance of Nb3Sn wire can be achieved by reducing the effective filament size, deff, in order to reduce flux jumping and magnet instability. The deff can be reduced by increasing the number of sub-elements in the Nb-Sn composite precursor wire. However, the barrier to producing a higher sub-element count is wire breakage during drawing, caused by the presence of an unfavorable stress pattern within the copper-clad, Nb-Sn composite wire. This project involves the further development of a method for applying an axial compressive stress to the wire, thereby eliminating the damaging stress pattern before the wire enters the reduction die. Phase I will demonstrate that this method can be applied to a credible length of fine-filament-size Nb-Sn composite wire without breakage. In Phase II, the process will be scaled up to produce kilometer lengths of Nb3Sn wire for test magnet winding. Commercial Applications and other Benefits as described by the awardee: This project should result in a continuous wire extrusion apparatus that enables the production of multi-filament Nb3Sn superconductor wire with increased numbers of sub-elements. It would be an enabling technology for substantially improved magnet performance. The development will support the engineering goal for next-generation High Energy Particle Colliders to operate with high critical-current at 15 to 20 Tesla or more. Enhanced performance of superconductor wire also should have widespread commercial applications.