Optimizing Nb3Sn Conductors for High Field Applications

Flexibility of design means internal tin Nb3Sn strands can be tailored for particular applications. For particle accelerator applications, the development work is focused on reducing the effective filament diameter whilst maintaining high J(c) and RRR. We will present our latest results on new distributed barrier strand designs that modify Nb, Sn, and Cll ratios to enhance RRR and maintain J(c) in strands having subelement diameter of less than 45 mu m. For laboratory magnets, cryogen-free operation is becoming the norm. To that end, we are continuing to develop single barrier internal tin strands having minimal ac losses but high I-c values of critical current. For high field NMR magnets, where the highest J(c) in the highest magnetic field is critical, highest performance strand has average J(c) values over 1600 A/mm2 at 4.2 K, 15 T. We will also present summary of strand performance for the ITER TF coil and our latest results on RRP strand for cable-in-conduit applications.