AC susceptibility and filament coupling of multifilamentary superconducting wires

The authors have studied proximity effect coupling on multifilamentary wires by measuring AC susceptibility. AC susceptibilities were measured on three kinds of samples. One was a Nb-multifilamentary wire with a Cu matrix, and the others were NbTi wires differing in the matrix, Cu or CuNi. A peak of the proximity effect coupling loss was seen as a function of temperature. It was foud that the peak temperature depends strongly on the measuring field and filament spacing. It decreased consistently with an increase in the applied field and the filament spacing. The coupling depends on the matrix, and no coupling peak was observed for the CuNi matrix wire at temperatures above 4.2 K.>