Optimization of the high field critical current density in MF Nb3Sn for magnet use

We here report new high field critical current measurements on FM Nb3Sn conductors together with some bend test data on a conductor to be used for a 15 tesla magnet system. The results show that zero stress Jcvalues of 280 A/mm²(measured over the bronze+Nb cross section) at 15 tesla are obtained. These high values have now been obtained for 3 different composites from 3 different sources, suggesting that it should now be possible to specify high Jcfrom filamentary Nb3Sn with some confidence. We have also made measurements of Jcunder tensile stress in the field range 13-16 tesla, obtaining values of over 500 A/mm²at 15 tesla, approximately twice as large as those obtained in zero stress measurements. We also report on some room temperature bend test measurements for which no degradation in Jcwas observed until outer filament strains of at least 0.5% were reached.