Studies on structure and properties of in-situ V3Ga superconducting composite tapes

Recent scaling-up development of the in-situ processed V
3
Ga composite superconductor at NRIM is reported. Cu-V binary ingots were prepared by consumable arc-melting, and cold-worked into tapes of 100-300m in length. Inspection of the uniformity was carried out for the in-situ Cu-V tapes by measuring the electrical resistivity change at room temperature along the tape length, and the results were compared with the critical current density J
c
distribution of the final in-situ V
3
Ga tapes. The structure of the in-situ tapes, obtained by continuous Ga-dipping and diffusion heat treatment, were studied. The reacted layer is divided into two layers with different V
3
Ga morphology. The outer layer composed of globular V
3
Ga has a T
c
of 15.2K, while the inner layer composed of ribbon-like filamentary V
3
Ga has somewhat lower T
c
of 15-13.5K. Therefore, the observed J
c
characteristic is a combined contribution from both layers having a different magnetic field dependence of J
c
. The ribbon-like morphology in the inner layer is responsible for the J
c
anisotropy of the tapes. The J
c
-H characteristics of the in-situ V
3
Ga tape revealed by the present study are advantageous in constructing 15-17 Tesla class superconducting magnet.