Effect of strain on the critical current of Nb-Hf/Cu-Sn-Ga multifilamentary superconductors

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Abstract
The critical current of multifilamentary Nb‐Hf/Cu‐Sn‐Ga has been determined as a function of both field and strain at fields from 4 to 19 T. The strain dependence of the critical current is significantly reduced compared with that of commercial multifilamentary Nb3Sn superconductors. This reduced strain sensitivity, coupled with an enhanced critical‐current density above 12 T, make this a candidate material for economic high‐field magnet construction. An analysis of the data in terms of the strain scaling law indicates that the Hf and Ga additives do not produce this improvement through a decrease in the strain sensitivity of the bulk upper critical field B*c2. Rather, they reduce the strain sensitivity of the critical current through a changed shape of the flux pinning curve and an enhancement in the strain‐free maximum value of B*c2 (B*c2m = 25 T for Nb‐Hf/Cu‐Sn‐Ga versus 21 T for Nb3Sn).