Distributed Optical Fibre Radiation and Temperature Sensor (DOFRS) Iacopo Toccafondo, EN-EA

Outline Introduction & Motivations Distributed Optical Fiber Radiation Sensor (DOFRS) based on RIA Distributed radiation measurements at CHARM PSB Installation & Further Work

Introduction Concerns High radiation levels Ensuring reliability and safety of the accelerator complex Equipment groups rely on accurate dosimetry for lifetime prediction Currently Monitoring systems Designing and installing radiation resistant components Regular maintenance, replacement/relocalization Limitations Monitoring systems are discrete/punctual, only partially online Frequent maintenance due to conservative life estimation approach

Motivation Provide accurate online distributed dosimetry Increasing safety Cost-effective implementation Future collider projects => Necessity of a cost-efficient, implementable and performant solution!

Concept - Distributed measurements Conventional (discrete) Optical Fibre Based (distributed) Online monitoring < 1m spatial resolution

Radiation effects on Silica-based optical fibers Radiation Induced Attenuation (RIA): increase in the glass linear attenuation through an increase of the linear absorption due to radiation-induced defects. Impact on RIA: The fiber composition an structure: Co-dopants such as germanium (Ge), phosphorus (P), aluminum (Al), fluorine (F) = > different radiation response Single or multi-mode Radiative environment characteristics: Dose dependency Dose rate dependency Temperature dependency Application parameters: Launched optical power wavelength E. Regnier et al., “Low-Dose Radiation-Induced Attenuation at InfraRed Wavelengths for P-Doped, Ge-Doped and Pure-Silica-Core Optical Fibres”, IEEE Transactions on Nuclear Science, Vol. 54., NO 4, August 2007

Distributed Optical Fiber Radiation Sensor (DOFRS) based on RIA Optical Time Domain Reflectometry OTDR based Control Unit Optical Fibre Backscattered light Distance (km) Light Intensity (dB)

Distributed Optical Fiber Radiation Sensor (DOFRS) based on RIA Optical fibre based radiation sensing Ionizing radiation OTDR based Control Unit Conventional Distance (km) Light Intensity (dB) Distance (km) Dose (Gy)

Distributed OTDR radiation sensing at CHARM 24 GeV/c, p 130 m long fibre path Two heights around the shielding: 95 cm & 280 cm above ground Wide range of dose rates Target Optical Fibre Adapted from the CHARM facility webpage Equipment: EXFO FTB500 with two high dynamic range OTDR modules SMF (850 nm & 1300 nm) & MMF (1310 nm & 1550 nm) Available pulse duration: 5 ns up to 20 µs Measurement time: 30 s up to 180 s

Distributed OTDR radiation sensing at CHARM J-fiber MMF, pulse width: 10 ns, acquisition time: 30 s, Al-h target Correct detection and localization of the four major dose peaks Detecting dose variations down to 10-15 Gy

Distributed OTDR radiation sensing at CHARM J-fiber MMF, pulse width: 10 ns, acquisition time: 180 s, Cu target After 10 h 37 min

Distributed OTDR radiation sensing at CHARM J-fiber MMF, pulse width: 10 ns, acquisition time: 180 s, Cu target After 16 h 37 min

Distributed OTDR radiation sensing at CHARM J-fiber MMF, pulse width: 10 ns, acquisition time: 180 s, Cu target After 25 h 57 min

Test installation in the PSB First in-field deployment at CERN: installation in the Proton Synchrotron Booster (PSB) Targeting full coverage (~157 m) Dose range from few tens Gy/y up to 100 kGy/y Up to a factor 10 reduction J.P. Saraiva and M.Brugger, “CERN-ACC-NOTE-2015-0042”, 2015 Post LS2, LINAC4 => reaching 2 GeV!

Test installation in the PSB - Status Approved Engineering Change Request (ECR) Installation of a metallic structure to support control RACK during week 37 Installation of RACK and fibre infrastructure during the EYETS 2016-2017 Installation and testing of equipment, end of EYETS 2016-2017

Further Work – Fibre Selection Characterizing commercial optical fibres At CC60 and CHARM facilities (CERN) Outside: Fraunhofer INT, others Purchasing from Fibrecore (P-doped cladding) and LEONI, any other? Corning doesn’t have any radiation sensitive fibre Draka (Italy) neither... OFS has a does rate dependency Characterizing optical fibres from ixBlue Fibres co-designed by LHCurien St-Etienne => highly promising PCe fibres – starting 14/09/2016 at CHARM P-doped => testing at CHARM? HACC => testing at CHARM? Designing optical fibres with ixBlue and LHCurien

Development of customized control unit - Status Meeting with Scuola Superiore Sant’Anna and INFIBRA Technologies held in Pisa on the 27/05/2016 => discussed two possible approaches Control unit: necessary hardware and software developed and configure to control two commercially available sensors => OTDR + Raman DTS => Market survey being carried out to assess if commercially OTDR boards are available and at what cost - ongoing Hybrid solution: adapting an existing highly performant Raman DTS developed by INFIBRA to be also used as OTDR => photobleaching effects due to coding need to be assessed – to be started

Development of customized control unit - Status Acquisition, data processing and results visualization interface, currently being developed in Python - ongoing EN/STI-ECE will take over the LabView implementation of the above and TIMBER logging => useful both for PSB and possibly for the custom control unit

Open Questions For a chosen fibre, would it be worth studying the possible impact of radiation type? Protons, neutrons, gamma etc... Systematic study of photobleaching on a P-doped fibre For a given launched optical wavelength do we only bleach the associated/corresponding color center or also others? Influence of coding (train of pulses) on photobleaching effects?

Many thanks for your attention! iacopo.toccafondo@cern.ch