Effect of transverse compressive stress on the critical current of cabled Nb3Sn conductor

A test apparatus has been designed and built for the investigation of cabled conductors subjected to transverse load. The apparatus permits measurement of compressive stress on a loaded multistage flat cable when a transport current is applied to one of its constituent subcables. With the apparatus, the critical-current behavior of a solder-filled Nb₃ Sn cable made by the external diffusion method exposed to transverse loads up to 165 MPa, was investigated. A field-dependent degradation of the critical current was found. The effect is completely reversible up to about 100 MPa. Solder-filled cables as used in large-current applications are less sensitive to transverse compressive stress than single wires. A 150 MPa compressive load on the SULTAN cable, for example, degrades the critical current by 31% at 11 T. This is still a high enough value in view of the large transverse compressive stress acting on conductors required for fusion magnets