Characterization of High $J_{c}$ ${\rm Nb}_{3}{\rm Sn}$ Strands for the Series-Connected Hybrid

The series-connected hybrid magnet under construction at the National High Magnetic Field Laboratory uses cable-in-conduit-conductor with high Jc Nb₃Sn strands. One of the candidate Nb₃Sn strands is made by the restacked-rod process with a nominal Jc of ~ 2400A/mm2. We characterized the J_c as a function of axial and transverse strain, magnetic field and temperature. The Jc-strain measurements have been carried out by a straight pull device and two different Walters spring probes. In addition, we have investigated the effect of the Nb₃Sn reaction heat treatment temperature on the irreversible strain. We found that the irreversible strain increases with the heat treatment temperature. Our results indicate that, in addition to its high J _c, this type of strand has moderate strain sensitivity, therefore is suitable for the application of the series-connected hybrid magnet.