Transport Critical Current Densities and $n$ -Values of Multifilamentary $\hbox {MgB}_{2}$ Wires at

A series of high-performing continuous-tube-filling-forming-fabricated (CTFF) powder-in-tube-type (PIT) MgB₂ strands have been prepared, with critical current densities, J_cs, higher than 1.30×10⁵ A/cm² and n-values above 30 at 4.2 K, 5 T. The transport J_cs and corresponding n-values of a selected sample C1 were reported at temperatures, T, of 4.2-30 K and magnetic fields, B, of 0-12 T. The J_c - B data were fitted by Eisterer´s percolation model and the temperature dependences of the fitting parameters were analyzed. The n - J_c curves showed a power law relationship n∞J_c^m, also previously observed in state-of-the-art monocore MgB₂ wires. Further analysis revealed that, like monofilamentary wires, the n(B, T) of this multifilamentary strand can also be estimated for all B and T based on the results of transport voltage-current (V- I) measurements made at one arbitrarily chosen temperature.