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

We report comprehensive data for the magnetic field (B < 14.5 T), temperature (4.2 K les T > les 14 K) and uniaxial applied strain dependence (-1% < epsiv
_A
< 0.35%) of the critical current density (J
_C
) of an advanced internal-tin Nb
₃
Sn 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 J
_C
of the PORI Nb
₃
Sn strand was ~ 40% lower than optimized values. Despite the low J
_C
, 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 Nb
₃
Sn strands. By assuming that the strain dependence of the normalized effective upper critical field is similar to that specified for other advanced strands, the J
_C
(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 J
_C
strand provide evidence that the 6 free parameter scaling law can be expected to accurately characterize a wide range of advanced internal-tin Nb
₃
Sn strands. The index of transition or n value is described by a modified power law of the form n = 1 + rI
_C

^s
, where r and s are approximately constant with values 3.15 and 0.36 respectively.