Speaker
Description
High-temperature superconductors (e.g., REBCO) are key to developing high-field magnets for next-generation high-energy circular colliders and compact fusion reactors. The U.S. Magnet Development Program, in collaboration with industry, is advancing REBCO magnet technology through multi-tape CORC® wires. Conventional sensors (strain gauges and voltage taps) are becoming insufficient to provide the full strain distribution or precise localization of resistive transitions, limiting insights into the magnet performance. This work implements single-mode optical fibers for distributed fiber optic sensing (DFOS), enabling continuous strain measurements along a six-layer, 40-turn canted cosθ dipole magnet using high-temperature superconducting CORC® wires. Tests conducted at 77 K and 4.2 K, on both individual layers and the assembled coil, revealed coil deformation under mechanical and thermal loads, along with potential resistive transition locations. The optical fiber layout and installation were optimized to cover sensing distances of up to 45 m at cryogenic temperatures. The result demonstrates the feasibility of DFOS for detecting strain distributions along the coil during operation. The result also shows hysteresis behaviors and a linear correlation between Lorentz force and strain, allowing identification of resistive transition sites. This approach offers a practical method for monitoring larger magnet systems and may facilitate early detection of thermal runaway in high-temperature superconducting magnets.
