Unifying the strain and temperature scaling laws for the pinning force density in superconducting niobium-tin multifilamentary wires

Abstract

Systematic variable temperature measurements of the transport critical current density (Jc) tolerance to strain (ε), performed on a bronze processed niobium-tin multifilamentary wire in high magnetic fields up to 15 T, are reported. The results show that Bc2*(T,ε), the field at which the pinning force density (Fp) extrapolates to zero, can be written as Bc2*(0,ε)g[T/Tc*(ε)], where g is a function of the reduced temperature T/Tc*(ε) and Tc*(ε) is the temperature at which Bc2* extrapolates to zero. We propose a magnetic field, temperature, and strain scaling law for Fp which unifies Ekin’s strain scaling law and the Fietz–Webb variable temperature scaling law. It is of the form Fp=Jc×B=A(ε)[Bc2*(T,ε)]nbp(1-b)q, where n, p, and q are constants, A(ε) is a function of strain alone, and b is the reduced field B/Bc2*.