Investigation on I/sub c/(B, T), H/sub c2/(T), and microstructure of internal-tin Nb/sub 3/Sn wires

The magnetic field (in range 5-12 T) and temperature dependencies (in range 4.2-12 K) of the transport current density J/sub c/(B, T) and temperature dependence of upper critical field B/sub c2/(T) in internal-tin multifilamentary wires are presented. The Summers relations have been applied for evaluation of the experimental J/sub c/(T) and B/sub c2/(T) data. The fitting parameters C, T/sub cm/(0), and B/sub c2m/(0) has been defined as giving the best fit to the experimental data. The microstructure of Nb/sub 3/Sn filaments has been investigated by SEM. The particular features of the diffusion processes in internal tin wires lead to formation of the specific Nb/sub 3/Sn filaments microstructure associated with high critical current density which have been analyzed.