Optical fiber based sensors for low temperature and superconductors Antonella Chiuchiolo 4th EuCARD-2 Annual Meeting Glasgow 28 – 30 March 2017

Outline Fiber Optic Sensors for the TNA Fiber integration in the test facility SM18 FOS for cryogenic temperatures FOS for superconducting magnets Conclusions Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

Fiber Optic Sensors for TNA Fiber Optic Sensors FOR CRYogenic ApplicatiOns and Superconducting Magnets University of Sannio (IT) University of Napoli, Federico II (IT) University of Padova (IT) University of Debrecen (HU) Institute of Polymers, Composites and Biomedical materials (IT) 1st access granted 20th of November 2013 …to develop a non intrusive technology based on FOS for strain and temperature monitoring in the new generation of superconducting magnet and cryogenic devices… Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

Horizon 2020 Universities Industries Research Institutes Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

Fiber Optic Sensors for TNA no commercial available FOS for cryogenic applications and superconducting magnets Assessed Technology Small size and lightweight Immunity to electromagnetic interference Intrinsic electrical insulation Radiation hardness capability Wide operating temperature range Multiplexing Innovation Fiber Bragg grating (FBG) sensors Rayleigh scattering distributed sensors Wiring reduction in a complex environment Remote monitoring No heat-leak into the cryogenic bath Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

Fiber Bragg Grating sensor Cladding Core Broadband light FBG: longitudinal periodic variation of the refractive index in the optical fiber core DlB (T, e) lB: Bragg Wavelength neff : effective refractive index of the core Λ: grating period Strain and Temperature sensitive: : photo elastic coefficient : thermo-optic coefficient : thermal expansion coefficient Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

FBG for Cryogenic FBG temperature sensitivity: 8 - 12 pm/K @ room T < 0.1 pm/K below 50 K Bare FBG no suitable for cryogenic temperature! Bare FBG Coated FBG The thermal response of a bonded or embedded FBG is dominated by the thermal expansion/contraction of the host material [H. Zhang et al. IEEE Transactions oh applied superconductivity, VOL. 18, NO. 2, 2008] Commercial Polyimide 30 mm thickness 12 mm 2 mm 5 mm 25 mm Customized PMMA 5 mm thickness Customized Epoxy 2 mm thickness 30 mm Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

Fiber integration in the test facility SM18 Sensors Single Mode fiber Commercial sensors Customized sensors Data Acquisition System Optical Interrogators: sm125, sm130 and Hyperion modules 4 channels , 2 Hz - 1 KHz, 90 – 160 nm Connections Fusion Splice Machine for fiber reparation Optical connectors and feedthrough to equip the test facility Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

Fiber integration in the test facility SM18 Vertical cryostat for testing magnets down to 4.2 K and 1.9 K: Liquid and Superfluid Helium Horizontal cryostat for HTS cable of 20 to 60 meter length: Helium Gas cooling Horizontal benches RF test area Visitors Cryogenics Vertical cryostats SC - Link For magnet cold powering up to 30 kA Cluster D Fiber Lab Cryogen free cryostat for testing FOS with 4.2 K Pulse Tube Refrigerator Vertical cryostat for testing mechanical properties of large magnet structures down to 77 K: Liquid Nitrogen Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

FBG characterization in the cryo cooler Dedicated cryogen- free test station He gas cooling down to 4 K with Pulse Tube refrigerator Temperature control Material study Sensors Calibration FBG and reference sensors set-up Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

FBG characterization in the cryo cooler Material study Sensitivity improvement Design optimization Sensors calibration Non linearity Repeatability along the cycles ST below 40 K: 1 pm/K ST @ 30 K: 13 pm/K ST @ 30 K: 15 pm/K Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

FBG for cryostat temperature monitoring Integration in the Superconducting Link horizontal cryostat He gas cooling 20-m-long MgB2 cable characterization He gas temperature monitoring over 20 m with calibrated FBGs and distributed Rayleigh scattering based sensors Connection side Wiring reduction: 4 CCS: 16 wires 4 FBG: 2 wires Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

FBG for cryostat temperature monitoring He gas temperature monitoring over 20 m with calibrated FBGs and distributed Rayleigh scattering based sensors FBGs: agreement with CCS within 1 K at 30 K Rayleigh scattering: map over distance with spatial resolution of 5 cm Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

FBG for superconducting magnets Integration in the magnet structures and coils Nb3Sn racetrack short model coils and quadrupoles High Temperature Superconducting magnets (H.Bajas talk) Temperature monitoring Strain monitoring during magnet fabrication and operation Nb3Sn Racetrack coil Magnet assembly Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

FBG for superconducting magnets Temperature monitoring inside the coil Magnet cool down from 300 to 1.9 K Strain monitoring inside the coil Magnet powering to 15 kA @ 1.9 K FBG Coil Temperature Cernox cryostat temperature Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

Publications Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow

Conclusions The SM18 test facility is now fully equipped for FOS integration and tests at cryogenic temperature software integration in the facility needs further development FBG for cryogenic temperature monitoring have been developed material study is still needed to enhance the sensitivity at 4 K FBG and Rayleigh scattering based sensors can be integrated in the facility cryostats for temperature monitoring Sensors packaging solution needs further development FBG can monitor the magnet thermo-mechanical behaviour of the magnet from fabrication to operation Integration needs to be improved Distributed sensors solution needs to be implemented Antonella Chiuchiolo - 4th EuCARD-2 Annual Meeting - Glasgow