Effects of Reaction Temperature and Alloying on Performance of Restack-Rod-Process ${\rm Nb}_{3}{\rm Sn}$

Final reactions of 48 or 50 hours were given in a range of temperature from 635
^o
C to 695
^o
C to high-J
_c
Ta- and Ti-alloyed Restack-Rod-Process Nb
₃
Sn 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)
₃
Sn strand designs investigated displayed peak J
_c
values of ~3000 A/mm
²
at 12 T and ~at 1500 A/mm
²
at 15 T for 665 and 680
^o
C 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.