Excess magnetization due to the presence of the matrix in a commercialized ultra fine multifilamentary NbTi composite with very fine filaments and Cu30%Ni matrix

We are studying the relation between the occurrence of the proximity effect coupling and the a.c. critical current degradation at low field in an ultra line multifilamentary NbTi superconducting composite for a.c. use. The occurrence of the proximity effect coupling between the ultra fine filaments across the Cu30%Ni matrix in commercialized a.c. wires was confirmed by comparing magnetization for two wires with and without matrix. Excess magnetization due to the proximity effect coupling was observed in both magnetization of the initial magnetization curves and the hysteresis loop for the clad wire at low field. Based on the results, the a.c. quench current degradation mechanism for these a.c. wires at low field is discussed.