Internal-Tin Nb/Sn strand with distributed barrier that will not leak Sn during heat treatment

Nb3Sn superconducting strands, used in magnets for high energy physics experiments, are heat treated at reduced temperatures and for reduced times, to enable a Relative Resistance Ratio (RRR) greater than 50 in the strand and stability at low fields. This practice reduces the non-copper Jc by 10-15%. This project will demonstrate a new approach that will prevent Sn leakage during heat treatment. This approach will enable the heat treatment to be applied for the maximum time and at the maximum temperature, as needed to produce and maintain a non-copper Jc in the 3000 A/mm2 range at 12T- 4.2K, and greater than 1500 A/mm2 at 15T-4.2K. Phase I will involve the fabrication of strands that will have 37, 61, and 91 subelements in the restack at 0.7 mm diameter. The strands will be characterized for current density, AC losses, and RRR. Commercial Applications and other Benefits as described by the awardee: The largest market for Nb3Sn is currently for accelerator and fusion magnets. For example, tons of strands are needed for the ITER project. Other commercial applications include high field MRI and NMR systems, proton radiation for cancer treatment, superconducting magnetic energy storage, and high field magnetic separation.