A New Approach to Measure Magnetic Field of High-Temperature Superconducting Coil Based on Magneto-Optical Faraday Effect

Magnetic field monitoring devices are essential for studying and operating high-temperature superconducting (HTS) magnets. Apart fromconventional Hall sensor, passive optical fiber sensor is also an option formagnetic field monitoring. In this article, we proposed a novel access based on yttrium iron garnet magnetooptic (YM) sensor, which is one kind of optical fiber sensors, to measuremagnetic fields generated by an HTS double pancake coil. Moreover, we used a magnetic field bypass tube made of silicon steel material to expand themeasurement range of YMsensor. The test results of YM sensor in liquid nitrogen demonstrated that the YM sensor was benchmarked against Hall probe up to 24.7 mT at 77 K. Using a silicon steel tube to shield magnetic field could extend the fieldmeasurement range to 37.6 mT. YMsensor could be one of the promisingmethods formonitoring HTS magnet magnetic field.