The field, temperature and strain dependence of the critical current density of a powder-in-tubeNb3Sn superconducting strand

Abstract

We present critical current density (JC) data as a function of magnetic field, temperature (4.2 K≤T≤14 K) and intrinsicstrain (εI) for a high performance powder-in-tube (PIT)Nb3Sn strand. Although the critical current density is very high, it isdemonstrated that there is no stronger strain sensitivity than forNb3Sn strands of other types and that the reversible strain window encompasses at least−0.60%<εI<0.25%. Then-value ofthe PIT Nb3Sn strand, derived from the electric field–current density (E–J) characteristics, is two or three times larger than those of strandsmade using other production processes. However, the normalizedn-index asa function of intrinsic strain still shows a similar behaviour to those for other strands. The relation betweenthe n-index and the critical current is described by the empirical power law of the formn = 1+rICs, wherer ands are approximately 3 and 0.5 respectively. We conclude that the increase inJC andthe n-value for PIT strands is achieved while maintaining good tolerance to strain.