Development of Co-Extrusion Technology to Produce Aluminum Stabilized Superconducting Wire.

Pure copper is widely used in industry as a stabilizing material in superconducting wires. Copper posseses excellent thermal and electrical properties. It is mechanically compatible with NbTi superconducting filaments relatively inexpensive and provides sufficient stabilization of a standard under normal operating conditions. Copper stabilizers can routinely provide RRR values (resistance measured at room temperature/resistance at 10 K) as high as 200 or even 300 in some cases. These values are suitable for most applications, however, magnets operating under exceptional conditions benefit significantly from higher RRR values in a stabilizing element. Supercon, Inc. proposes to investigate commercially viable techniques to clad a NbTi superconducting wire with high purity aluminum as the stabilizing element. Aluminum offers high RRR values (4000+ in commercially available aluminum), light weight and good thermal conductivity. These properties allow superconducting magnets to be conductively cooled using cryocoolers to eliminate the need for liquid helium. These developments will introduce the application of superconducting technology in remote locations where liquid helium may not be available. The Phase I program will investigate and evaluate two existing cladding techniques. The best process will be selected based on several criteria with tooling and machine modification designs completed in Phase I. The program objective is to develop the capacity to clad a wide range of wire sizes.