ACHIEVEMENT OF HIGH-CURRENT DENSITY IN NB-TI SUPERCONDUCTING MULTIFILAMENTARY WIRES BY INTRODUCING DESIGNED ARTIFICIAL PINS

It is shown theoretically that a further increase in the overall critical current density of Nb - Ti multifilamentary wire is possible by introducing artificial pinning centres into Nb - Ti filaments in a specified fashion. As the first step towards experimental confirmation of theoretical predictions of the summation of individual forces, Nb - Ti monofilamentary wires were fabricated, in each of which were embedded fine filamentary Nb rods with a given diameter and spacing, to act as artificial pinning centres. These wires show higher critical current densities than have been reported so far, at fields lower than almost-equal-to 2 T. Although the quantitative agreement between the theoretical and observed results is not yet very satisfactory, further investigation of the pinning characteristics using various artificial pins leads to a new stage where it is possible to design the wire parameters for obtaining the required characteristics of critical current density.