Development of a Novel Method to Efficiently Measure Critical Bending Diameter of 2G HTS Tapes

High critical current density is desired for cables adopted in fusion or accelerator applications. The bending diameter of REBCO tapes is very important for the preparation of such cables. The bending diameter of REBCO tape is related to many factors. It is necessary to identify the most important factors determining the bending diameter by experiments. In this article, a new measurement method for bending diameter is developed. Short samples are taken from individual tapes in a large batch and connected in series into one long piece for bending diameter measurement. This way, a large batch of tapes can be efficiently assessed in one go. The samples prepared by Shanghai Superconducting Technology Co., Ltd. (SST) have been tested. It is concluded that the critical bending diameter of the tapes, which we define that the critical current attenuation is less than 10%, is closely related to its thickness, stiffness, superconducting layer thickness, and copper plating thickness. The composition of the superconducting layer has little effect on it. By testing the tapes prepared by SST in large quantity, it is found that when the REBCO faces inward during bending, tapes plated with 5 and 10
μ
m copper on one side only have smaller critical bending diameter than tapes plated with copper on both sides. The current has no attenuation when the bending diameter is 2.6 mm. When REBCO faces outward, copper plating has little effect on the critical bending diameter, which varies between 6 and 14 mm.