Strain Scaling Law and the Prediction of Uniaxial and Bending Strain Effects in Multifilamentary Superconductors

Abstract

Recently it was shown¹ that at 4.2 K the critical pinning-force density F in a wide range of practical conductors obeys a scaling law of the form:

$$F = {[B_{c2}^*(\varepsilon )]^n}\,f(b)$$

((1))

where $B_{c2}^*$ is the bulk upper-critical field at 4.2 K and f(b) is a function only of the reduced magnetic field $b \equiv B/B_{c2}^*.$ For Nb₃Sn conductors, n = 1 ± 0.3. This relation was found to hold for both compressive and tensile intrinsic strain, and is expected to be limited in validity only by the irreversible strain point² where filament breakage becomes significant (typically at intrinsic tensile strains greater than 0.4 – 0.7% for most highly-reacted Nb₃Sn conductors²).