INTERNAL TIN Nb3Sn CONDUCTORS FOR PARTICLE ACCELERATOR AND FUSION APPLICATIONS

The past several years have seen a significant improvement in the maximum critical current density (Jc) in Nb3Sn strand. However for many applications, parameters besides high Jc values are paramount. For fusion applications such as ITER, we have developed single‐barrier internal tin strands having non‐Cu Jc values over 1000 A/mm2 (12 T, 4.2 K) with hysteresis losses less than 1000 mJ/cm3. Our most recent results are presented, with the goal of maintaining the high Jc but further reducing the losses. For high field magnet applications, higher Jc values are obtained using a distributed barrier approach. Results will be presented on a new high Jc Nb3Sn strand that is made with (Nb,Ti)3Sn instead of (Nb,Ta)3Sn. This (Nb,Ti)3Sn strand has a Jc value of 3000 A/mm2 (12 T, 4.2 K), but has improved higher field performance compared with our standard (Nb,Ta)3Sn material, reaching 1700 A/mm2 at 15 T, with further optimizations perhaps still possible. To reduce the effective filament diameter in these high Jc strand...