Effects of stresses, induced by thermal contraction of a bronze matrix, on the superconducting properties of Nb3Sn wires

Abstract

The superconducting critical temperature Tc and high-magnetic-field critical-current densities Jc have been measured on bronze-processed Nb3Sn single-core wires prior to and after removing the bronze cladding. Both Tc and Jc, at high magnetic fields, are increased after removal of the cladding. Tc measurements on a series of wires with various core-to-matrix ratios R show that the depression in Tc increases as R decreases. The results are interpreted in terms of a stress imposed on the Nb3Sn layer by the thermal contraction of the outer bronze cladding. Results point to the possibility of a martensitic phase transformation occurring in the bronze-clad Nb3Sn wires.