Cryogenic Fiber Optic Sensors for Superconducting Magnets and Power Transmission Lines in High Energy Physics Applications

by Antonella Chiuchiolo (CERN)

Tuesday 1 Mar 2016, 14:00 → 15:00 Europe/Zurich

30/7-010 (CERN)

In the framework of the Luminosity upgrade of the Large Hadron Collider (HL - LHC), the development of the new generation of Nb3Sn-based accelerator magnets on and MgB2-based superconducting power transmission lines will require technology innovation also for instrumentation. Fiber optic sensors (FOS) are proposed, for strain and temperature monitoring, for their well-known advantages like the small size, the intrinsic electrical insulation, immunity to electromagnetic interferences and multiplexing. The development of polymer coated FBG sensors has required advances in the material selection, fabrication process and test facility implementation. Their temperature characterization (in the range 300 - 4.2 K) has been performed using a dedicated cryo-cooler. The FBG sensors, combined to the Rayleigh-based distributed sensors, were then used in a 20-m-long MgB2 power transmission line for monitoring the temperature of the helium gas down to 30 K. FBG sensors in bonded and embedded configuration have been also integrated in sub-scale Nb3Sn dipole magnets for monitoring the main stages of the magnet service life. Experimental results have been reported during magnet assembly and thermal cycle down to 1.9 K, during energization up to 15.5 kA and quench monitoring under high magnetic fields (up to 13.5 T). The presentation will give an overview of the recent advances in the FOS development for cryogenic applications, with an introduction to the dedicated fiber laboratory that has been set up at SM18 for FOS characterization. The results of the sensors integration in the Superconducting Link and in the Nb3Sn magnets built at CERN will be discussed as well.