RIOF Quench Detection in Low-frequency HTS magnets subject to vibrations

nd deployed by the Department of Defense (DoD), are necessary to maintain and advance the U.S. naval defense and warfighting capability. The implementation of HTS SCMs into systems has been impeded by the inability to reliably detect and protect the SCMs against fault conditions that lead to a magnet quench. This is especially true for HTS SCMs operated in AC, where the base-line voltage resulting from AC operation is orders of magnitude greater than the voltage signal related to an incipient quench, rendering voltage-based methods virtually useless for quench detection. An alternative technology for quench detection is based on Rayleigh-backscattering Interrogated Optical Fibers (RIOF). In this approach, the optical fiber is a distributed sensor that is embedded in the SCM and offers the capability for rapid and accurate detection of changes in temperature and strain as a function of location within the SCM. Because of its immunity to EM noise, the high spatial resolution and the high temperature and strain sensitivity, RIOF quench detection provides a capability that voltage-based measurements cannot provide.Although the proposing teams prior work has successfully advanced the RIOF quench detection technique for HTS SCM in DC operation, basic research is needed to study the effects of AC operation on the optical fiber signal at a fundamental level. Additionally, for the technique to be relevant to SCMs developed by the DoD, the sensing system needs to be able to operate in a vibration field and be capable to interrogate several kilometers of optical fiber.The proposed research project aims at addressing the fundamental challenges associated with extending the effectiveness of an optical fiber quench detection system to HTS magnets that are relevant to the Navy. Specific Objectives include understanding and advancing RIOF quench detection to low-frequency AC-operated HTS coils, analyzing the effects of vibrations on the signal measured by optical fibers, developing solutions to mitigate potential undesired effects of AC current and vibrations on fault detection performance, and advance alternative interrogation techniques to allow for a single-fiber sensing length of several kilometers.The technical approach to achieve the proposed objectives generally revolves around experimentally subjecting HTS coils with integrated optical fibers to AC operation and vibrations and analyzing the effects on the optical fiber signal. Experiments are designed to distinguish effects and indicate the underlying mechanisms that connect the stimulus to the effect on the detection signal.Successful completion ofthe proposed project will create knowledge on the behavior and effectiveness of the RIOF quench detection technique when HTS coils are operated in AC and subject to vibrations. Furthermore, a successful completion of the proposed researchensing lengths of over a kilometer closer to fruition. The results will indicate whether the effectiveness that has been previouslydemonstrated in DC translates to AC operation, will determine and quantify the effects of vibrations, will propose and carry out preliminary test of potential solutions, and will produce insight on future development & implementation research that is needed to transform the technique into a system. Ultimately, the application of the fundamental knowledge created by this project will lead to providing the DoD with a failure protection and prevention system that will enable deployment of capabilities based on HTS SCMs.It isimportant to note that the need for quench protection in HTS SCMs is ubiquitous, and thus the proposed research will impact many of