Fabrication technology and performance test for optical fiber encapsulated high temperature superconducting tapes

Abstract Realizing fast and accurate quench detection is a great challenge for the application of long high temperature superconducting (HTS) conductors. The combination of distributed temperature sensing (DTS) system and optical fiber encapsulated high temperature superconducting (OFE-HTS) tape may become a promising approach to solve this problem. As a recently proposed composite HTS tape, its properties have not been studied systematically yet. Therefore, in this study, the electromagnetic and thermal behaviors of the OFE-HTS and traditional HTS tapes are compared by the finite element simulation technology. The simulation results predict that the embedded optical fibers will hardly change the original electric, magnetic and thermal characteristics of the HTS tapes. Besides, the detailed fabrication method of the OFE-HTS tape is introduced, and the composite tape performances including structure integrity, critical current uniformity, anti-bending/tensile force and quench response are tested seriatim. According to the microscope and X-ray detection results, the optical fibers are fully embedded in the OFE-HTS tape through the presented fabrication process. The critical current uniformity test results show the average critical current of the prepared 76 m-long OFE-HTS tape is about 520 A, and the its uniformity variation is about ± 4%. The prepared OFE-HTS and traditional tapes have similar anti-bending/tensile properties. Finally, to check the effectiveness of the embedded optical fiber for quench detection, the fabricated OFE-HTS coil is tested. The quench detection results show that the temperatures in the same area measured by the optimized DTS system and a thermocouple are similar. Moreover, the temperature response ability of the optimized DTS system is better than that of the thermocouples, and the optimized DTS system is able to effectively avoid environmental electromagnetic field interference.