The Magnetic Field, Temperature and Strain Dependence of the Critical Current of a ${\rm Nb}_{3}{\rm Sn}$ Strand Using a Six Free-Parameter Scaling Law

Abstract

We report comprehensive data for the magnetic field (B les 14 K) and uniaxial applied strain dependence (-1% < epsivA < 0.35%) of the critical current density (JC) of an advanced internal-tin Nb3Sn strand developed as part of the International Thermonuclear Experimental Reactor (ITER) program manufactured by Luvata PORI. A very short heat-treatment was used so that JC of the PORI Nb3Sn strand was ~ 40% lower than optimized values. Despite the low JC, we find that the normalized strain sensitivity of the critical current at 14 T and 4.2 K is similar to other advanced internal-tin Nb3Sn strands. By assuming that the strain dependence of the normalized effective upper critical field is similar to that specified for other advanced strands, the JC(B,T,epsiv) data of the PORI strand can be accurately parameterized using a scaling law with just 6 free parameters. Hence the results presented here on a low JC strand provide evidence that the 6 free parameter scaling law can be expected to accurately characterize a wide range of advanced internal-tin Nb3Sn strands. The index of transition or n value is described by a modified power law of the form n = 1 + rIC s, where r and s are approximately constant with values 3.15 and 0.36 respectively.