Multi-Purpose Fiber Optic Sensors for HTS Magnets

Magnets using new high temperature superconductor (HTS) materials are showing great promise for high magnetic field and/or radiation environment applications such as particle accelerators. However, the development and operation of these magnets is limited because appropriate sensors and diagnostic systems are not yet available for monitoring the manufacturing and operational processes. In this project, optical fibers will be imbedded within HTS magnets to monitor strain, temperature, and irradiation, and to detect quenches. In the case of Bi2212 superconductor, the fiber will be used as a heat treatment process monitor to ensure that the entire magnet has reached thermal equilibrium. In Phase I, the optical fibers were shown to be compatible with HTS magnets by processing them in contact with Bi2212 wire in an oxygen environment up to 890oC. Techniques were investigated for imbedding the fibers in coil packages for process monitoring, local strain and temperature monitoring, irradiation accumulation, and quench detection. In Phase II, other coating materials will be deposited onto optical fibers and tested for compatibility with HTS materials and processing methods, and for improved temperature and strain sensitivity at low temperature. Commercial Applications and other Benefits as described by the awardee: The sensitive diagnostics for monitor strain and temperature should benefit the development and operation of magnets constructed from HTS, thereby facilitating the use of HTS magnets for many scientific (including plasma-confinement systems for fusion reactors), medical (including NMR), military, and power applications.