Advances in Fiber Optic Sensors Technology Development for Temperature and Strain Measurements in Superconducting Magnets and Devices

Abstract

Abstract-The luminosity upgrade of the Large HadronCollider (HL-LHC) requires the development of a new generation of superconducting magnets based on Nb3S n technology. In order to monitor the magnet thermo-mechanical behaviour during its service life, from the coil fabrication to the magnet operation, reliable sensing systems need to be implemented. In the framework of the FP7 European project EUCARD, Nb3S n racetrack coils are developed as test beds for the fabrication validation, the cable characterization and the instrumentation development.Fiber optic sensors (FOS ) based on Fiber Bragg Grating (FBG) technology have been embedded in the coils of the S hort Model Coil (S MC) magnet. The FBG sensitivity to both temperature and strain required the development of a solution able to separate the mechanical and temperature effects. This work presents the feasibility study of the implementation of embedded FBG sensors for the temperature and strain monitoring of the 11 T type conductor. We aim to monitor and register these effects during the coil fabrication and cool down in a standalone configuration.  Index Terms-Fiber optic sensors, Fiber Bragg Grating, racetrack coil, Nb3Sn

Quench Detection and Protection for High-Temperature Superconductor Accelerator Magnets

“…All of them rely on detecting a change in the optical properties of the fiber, due to either a local thermal expansion (hence temperature sensing) or thermally induced variation of strain. Discreet sensors based on fiber Bragg gratings (FBGs) [47][48][49][50] have been found to perform well at cryogenic temperatures and detect variations of temperature and strain. Gratings are integrated along the length of the fiber path and interrogated optically in order to measure thermally induced local variations of their period.…”

Advancing Superconducting Magnet Diagnostics for Future Colliders

“…• Establish fiber-optic based diagnostic capabilities through the use of Fiber Bragg Grating (FBG) and Rayleigh scattering-based sensors to measure elastic deformations, localize hot spots (especially in HTS magnets) and probe mechanical disturbances in SC cables [17].…”

VIPER: an industrially scalable high-current high-temperature superconductor cable

“…Quenches in response to external heater pulses were almost exclusively observed at T < 20 K and Iop/Ic > 1.0. Temperature excursions on the Delta cable were monitored with two fiber optic quench detection technologies: an array of discrete fiber Bragg gratings (FBG) [44] and a distributed single ultra-long FBG (ULFBG) [48]. Each technique uses a variation of monitoring the temperature-dependent spectral response of fiber Bragg gratings inscribed into optical fibers.…”