Transport Properties up to 1000 A of ${\rm Nb}_{3}{\rm Sn}$ Wires Under Transverse Compressive Stress

The effect of transverse compressive stress on the superconducting transport currents of multifilamentary Nb ₃ Sn wires have been measured at 19 T using a newly developed probe allowing gauge lengths as long as 125 mm. Two different wire types have been studied: an experimental Bronze Route wire (from our laboratory) with 14'641 filaments of 4.5 mum diameter and a RRP internal Sn wire (from OST), with 60 filament bundles, each having a diameter of 70 mum. It was found that the RRP wire exhibits higher stress sensitivity. For the Bronze Route wire our data also comprise a comparison of the I _c behavior for rectangular and round cross sections. The problem of current transfer has been solved using a new type of Walters spring (one turn). The spring has been cut parallel to the wire sample into two parts so the measured sample length covers a whole turn. One part can be moved axially and forces up to 40 kN are applicable. The new device will be used for the investigation of various types of superconducting wires, comprising Nb ₃ Sn and Nb ₃ Al, in view of their application in systems with high transverse compressive forces, in particular high field dipoles (e.g. NED).