Superconducting critical current density of bronze processed pure and alloyed Nb3Sn at very high magnetic fields (up to 24 T)

Abstract

Superconducting critical current densities J_c of pure and alloyed Nb₃Sn layers of bronze processed monofilamentary wires were measured at 1.8 and 4.2 K in magnetic fields up to 24 T. The maximum in J_c at 20 T was found for Nb₃Sn layers which were fabricated using (Nb ∼3.3 at. % Ti) cores, and the values of J_c were ∼670 and ∼370 A/mm² at 1.8 and 4.2 K, respectively. These values are ∼5 and ∼25 times greater than those for ‘‘pure’’ Nb₃Sn wires at these same temperatures. The functional dependence of J_c on the Ti content was also identical to that for the measured values of H_c2 vs Ti content for these wires. The maximum value of H_c2 of the wires with the matrix in place was 26.3 T for the wire which was fabricated from the core containing 3.3 at. % Ti in Nb.