Field dependence of the n-value and its relation with the critical current ofNb3Sn strands

Abstract

We find a simple expression for the field dependences of then-valuefor Nb3Sn strands which gives reasonable fits to empirical data. It is also found that a relationship between then-value and the critical current, which is obtained from an assumed reduction of theflux line lattice shearing pinning force due to thermal activation, can describethe field dependence of the critical current. Using the relation between then-value and the critical current, we propose a scaling law which we have called the Kramermodel including thermal activation. It is shown that the proposed scaling law can explainthe critical current data at 4.2 K, even at high field near the upper critical field. It is alsocompared with Ekin’s strain scaling law.