Characterization of $\hbox {Nb}_{3}\hbox {Sn}$ Strands for a 40-T Hybrid Magnetic Model Coil

A 40-T hybrid magnet under construction at the High Magnetic Field Laboratory of the Chinese Academy of Sciences will use cable-in-conduit conductors for its superconducting outsert. The design necessitates the use of high current density (J_c) Nb₃Sn strands (J_c ≥ 2100 A/mm² at 12 T/4.2 K). The high J_c restacked-rod-processed Nb₃Sn strand from Oxford Instruments Superconductor Technology was selected as one of the candidate strands. A series of tests was carried out to qualify the strand performance. Tests mainly included magnetization and critical current measurements as a function of axial strain, magnetic fields, and temperature. The test results are presented and discussed.