Effects of Reaction Temperature and Alloying on Performance of Restack-Rod-Process Nb3Sn

Final reactions of 48 or 50 hours were given in a range of temperature from 635 ^oC to 695 ^oC to high-J_c Ta- and Ti-alloyed Restack-Rod-Process Nb₃Sn strands to investigate the changes in critical current density and the superconducting properties. J_c is the current density in the non-copper region of the wire. Measurements of J_c were made at 4.2 K temperature and from 8 to 11.5 T field at BNL and from 12 to 16 T at OST, and these data were fitted to the Summers expression for J_c to extrapolate the scaling field . B_c2 ^*ldr All three(Nb, Ta)₃Sn strand designs investigated displayed peak J_c values of ~3000 A/mm² at 12 T and ~at 1500 A/mm² at 15 T for 665 and 680 ^oC reactions. B_c2 ^* increased monotonically with increasing reaction temperature, a (Nb, Ti)₃, By comparison, at each reaction temperature, a strand under development had a B_c2 ^* higher than any of the Ta-alloyed strands. This suggests that Ti-alloyed strands could improve high-field performance if further development can bring their J_c values closer to those of the Ta-alloyed strands. Other implications are also discussed.