Evaluation of the Critical Current Density of Multifilamentary ${rm Nb}_{3}{rm Sn}$ Wires From Magnetization Measurements

摘要

A simple model for evaluating the critical current density of multifilamentary ${rm Nb}_{3}{rm Sn}$ wires from magnetization measurements was examined. This model assumes that each sub-element is in good approximation a superconducting hollow cylinder, which limits its validity to powder-in-tube wires and wires whose filaments are completely merged within the sub-elements. The magnetic moment of short samples of four wire types was measured in a SQUID magnetometer at applied fields of up to 7 T in the temperature range from 4.2 to 15 K. The $J_{rm c}$ evaluation model discussed in this work was used to obtain critical current densities from the results of these measurements. The calculated $J_{rm c}$ values were compared to transport measurement results, and satisfactory agreement was found between the two data sets. Furthermore, it was shown by means of magnetization measurements of individual sub-elements that the coupling between the sub-elements in the wire samples has a negligible effect on such measurements.