Proofing tests of a fiber-reinforced type of niobium-tin superconductor by small coil experiments

We have been developing fiber-reinforced type of niobium-tin superconductor for a large-scale high field magnet. This conductor has a niobium-tin filament reinforced by a tantalum core of about 20-micrometer diameter. Tantalum is selected as a reinforcing material since it has good ductility with mechanical strength comparable to stainless steel. We have tested this conductor in the form of a small solenoid with the diameter of 50 mm under a backup magnetic field of 15 Tesla. Results of the test showed that it has a uniform superconducting property over a length of 250 meter. Furthermore, we developed another conductor with larger current carrying capacity and tested this conductor in the coil form. Strain measurement of the second coil revealed that the windings behave elastically within the range of operation.