The critical current density of filamentary Nb3Sn as a function of temperature and magnetic field

We have built and developed an apparatus which permits the reliable evaluation of Jc(B,T) for helically wound samples of superconductor. This apparatus is used in conjunction with The Oxford Hybrid Magnet which achieves a maximum field of 15.5T. The temperature range over which measurements can be made is 2 to 30K. Results on filamentary NbTi have already been published. We present here results of a highly detailed characterisation of an Nb3Sn filamentary conductor produced by the post-winding, high-temperature reaction of a Cu-Sn bronze - Nb composite which contains high purity copper florets and was developed at A.E.R.E. at Harwell. Jchas been measured as a function of temperature, in 0.5K increments, from 2K to 18K, at field levels ranging from 0T to 15T in 0.5T increments. We present also an empirical fit to the data. This was made possible by the near linear behaviour of the function over much of the range of practical interest. We believe these results could be of great interest to the designers of superconducting machines and devices.