Critical current of multifilamentary nb₃sn wire in high magnetic field

The critical current of copper-stabilized multifilamentary Nb₃Sn wire was measured in magnetic fields up to 18 T at 4.2 K, 2.85 K and 2.18 K. The conductor investigated in the experiment was fabricated by a “bronze” process. Its external diameter is 0.53 mm and it consists of 2886 filaments (5 μm dia.) in a bronze (13 wt%Sn). matrix. The measurements show that the conductor has excellent superconducting properties. For instance, J_c(N_b + bronze) of the sample heat treated for 100 hours at 700°C is as follows: at 4.2 K, 8 × 10⁴ A cm^-2 at 10 T, 6 × 10³ A cm^-2 at 18 T; at 2.18 K, 1×10⁵ A cm^-2 at 10 T and 1.5×10⁴ A cm^-2 at 18 T. The extrapolated values of Bc2, according to the scaling law for flux pinning, are 22 T and 23.8 T, at 4.2 K and 2.18 K respectively. Transition temperature results are also discussed.