The Influence of Various Strain Components on the Critical Parameters of Layer Shaped Nb₃Sn

Abstract

The critical current density inside various types of Nb₃Sn conductors is determined as a function of strain. For an axial strain this has led to the well-known “Scaling Law” proposed by Ekinl. The upper critical field is described as a function of the axial strain B _c2 (ε _a ). Then the critical current density as a function of the applied magnetic field J _c (B) gives the relation between current density and axial strain. It is concluded that the maximum in the upper critical field and the critical current density appears when the applied axial strain exactly cancels the thermally induced strain due to the shrinking of the matrix. The step from a single strain component to the complete strain tensor is made theoretically by using the symmetry of the Nb₃Sn lattice². This led to the conclusion that the distortional strain is the most important strain parameter to describe the strain dependence of the upper critical field.