Flexural properties of a MgB2 thin-film wire

Aiming to understand the bending characteristics of a MgB2 thin-film wire and utilize the wire in the design of superconducting magnets, we examined the degradation of critical current density J (c) due to bending. Six short MgB2 thin-film wires with a thickness of 1 mu m were prepared under the same deposition conditions. They were bent in different radii, and their J (c) were compared. The allowable bending radius at which J (c) does not degrade was 25.0 mm. As for MgB2 thin-film wires, thickening the film effectively increases the engineering critical current density J (e). On the basis of material mechanics, the allowable bending radius was estimated to be 25.5 mm when the film thickness increased to 10 mu m. The allowable bending radius of the MgB2 thin-film wire is sufficiently smaller than the radius of a typical superconducting coil, so it is not considered to be a barrier to fabricating a coil with the wire.