Static stress effects in superconducting composites Part I. Effect of uniaxial tensile stress on resistive critical field of Cu-Nb composites

摘要

Multifilamentary Cu-Nb in situ composite wires were subjected to tensile tests in liquid helium environment to study influence of the stress #sigma# on resistive critical field H_r of the composites. External magnetic field H was parallel to wire axis and 4-probe scheme for resistive measurements was applied. The wires had various diameters, that is they differed in their overall manufacturing deformation. Our experiments evidence that values of both the critical fields H_(r0) of the initial composites and stress sensitivity of the fields dH_r/d#sigma# are noticeably higher than those referenced for niobium. We conclude that it is the dislocation structure of Nb filaments and its effect on Ginsburg-Landau parameter and thermodynamic critical field H_c of the filaments that determine the observed dependences.