Distributed Optical Fiber Radiation and Temperature Sensing at High Energy Accelerators and Experiments Iacopo Toccafondo, EN-EA

Outline Introduction & Motivations Milestones & Goals for 2017-> LS2 Current Status Distributed radiation and temperature measurements PSB installation Urgent Matters Control unit/ Interrogator Fibres Conclusions & To-do List

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!

Milestones & Goals for 2017 -> LS2 Ultimate performance requirements, for machine monitoring: Total Ionizing Dose: from a few tens of Gy up to 100 kGy Dose resolution: 10% of the TID. Dose rate: from a few mGy/s up to a few Gy/s Spatial resolution: ≤ 1 m Temperature range: 15 °C – 35 °C, hot spots: 200 °C Temperature resolution: 1°C

Milestones & Goals for 2017 -> LS2 2018 2019 2020 PSB Installation to be completed during EYETS PSB measurement campaign Based on results and CHARM/CC60 characterizations => select fibre Control unit to be selected PS deployment to be approved and started YETS PS deployment to be finished during YETS PS measurement campaign Based on results further optimization of fibre/control unit SPS deployment to be approved and started at the beginning of LS2 => maybe earlier but when? LS2 Based on the results from the injectors measurement campaigns, deployment in LHC => needs however to be approved before LS2!!! LHC measurement campaigns From: https://lhc-commissioning.web.cern.ch/lhc-commissioning/schedule/LHC-long-term.htm

Current Status – Distributed Radiation Measurements Some promising results! Some limitations... ... on the fibre Early saturation of tested fibre ~ 15 kGy Identification/localisation of dose deposition events in a mixed-radiation environment Small dose rate dependency Dose resolution: ~ 10 Gy -15 Gy Probably Ge+P => need P-doped! Spatial resolution: 1 m

Current Status – Distributed Radiation Measurements Some promising results! Some limitations... ... on the OTDR http://www.exfo.com/fr/produits/tests-terrain/bu6-ecosysteme-ftb/plateformes/ftb-500 Limited dynamic range Identification/localisation of dose deposition events in a mixed-radiation environment Limited choice of wavelengths Dose resolution: ~ 10 Gy -15 Gy Spatial resolution: 1 m Need for optimization/customization

Current Status – Distributed Temperature Measurements Successful and accurate temperature measurement in mixed-radiation environment Temperature resolution: 1°C Spatial resolution: 1 m Measurement carried out with INFIBRA DTS @ 1064 nm in double-end configuration on radiation tolerant fibre

Current Status – PSB Installation First in-field deployment at CERN targeting an 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!

Current Status – PSB Installation Engineering Change Request (ECR) approved Metalic structure to support RACK - installed RACK and fibre structure – scheduled during EYETS Fibre cables (x2) to be blown – scheduled during EYETS Equipment – available/ready LabView acquistion/control/processing/logging on TIMBER interface – being developed Additional cables with new fibres – not yet scheduled

Urgent Matters – Control Unit / Interrogator Short Term Need to buy an additional OTDR for either PSB or facilities: EXFO? JDSU? VIAVI? ... ? LabView interface currently developed ad-hoc for EXFO device To be considered are performances, cost and delivery time.

Urgent Matters – Control Unit / Interrogator Long Term – Customization/Optimization Requirements Need to improve dynamic range of the control unit Injecting higher power levels? => P-doped fibres shouldn’t suffer from photobleaching at some specific wavelength, hence no limitation on this side. Implementation of advance coding techniques More freedom in the wavelength choice Pulse width and acquisition duration already satisfying on the EXFO FTB500

Urgent Matters – Control Unit / Interrogator Long Term/Large Scale Solution Commercial Device – OTDR for Radiation Sensing EXFO Performances of tested unit might not be sufficient for longer machines Depending on the modules one can improve performances => by how much? Should be assessed Integrated switches for multi-fibre interrogation Cost for large scale deployment is acceptable (~15 – 20 kCHF) Other companies such as JDSU, Tektronix, Fujikura Offering probably similar performances and prices A market survey could be carried out

Urgent Matters – Control Unit / Interrogator Long Term/Large Scale Solution Commercial Device – Raman DTS for Temperature Sensing Companies with which our collaboration ensures customization possibilities of the device: INFIBRA Technologies (Pisa) VIAVI

Urgent Matters – Control Unit / Interrogator Long Term/Large Scale Solution Commercial Device – Raman DTS for Temperature Sensing Other leading companies: APSensing advanced photonic (Böblingen, Germany) Lios Technology Gmbh, OFDR-based, (Cologne, Germany) ...

Urgent Matters – Control Unit / Interrogator Long Term/Large Scale Solution Customized/optimized solutions for both radiation and temperature sensing Hybrid scheme from Scuola Superiore Sant’Anna Adapting high performance long-range Raman DTS to interrogate two fibres: one for radiation sensing, the other for temperature sensing (double-end) The high peak power of the laser source together with the high sensitivity and low noise of the APDs can ensure a high dynamic range Single laser cuts costs => however we need more wavelegnths, so probably more sources indeed! Cost to be defined

Urgent Matters – Control Unit / Interrogator Long Term/Large Scale Solution Customized/optimized solutions for both radiation and temperature sensing Hybrid scheme from VIAVI Dual source/wavelengths on a single optical fibre for both radiation and temperature sensing Possibly longer sensing range for temperature as it is single end Highly complex to find a single fibre to be suitable for both applications! Cost to be defined

Optical Fibres Characterized fibres 3 MMF P-co-doped => 2 of them relatively suitable for radiation sensing (tested at CHARM) => early saturation + slight dose rate dependency 2 SMF P-co-doped => 1 of them discontinued, the second must still be analyzed Available cables Cable 1: containing the 3 above mentioned MMF + 1 SMF Ge- doped, + the above mentioned P-co-doped SMF Cable 2: radiation tolerant (MM) and resistant fibres (SM) We need more promising fibre candidates to be characterized! => P-doped?

Optical Fibres Fibres from ixBlue/Saint-Etienne What should be purchase? Fibres from leading manufacturers, e.g. Draka, Fujikura, OFS, Leoni, Corning… Not all of them have radiation sensitive fibres Fibres not explicitly designed for our application Composition often unknown A collaboration with one of these manufacturers could be beneficial in order to develop a suitable fibre together at a reasonable cost Fibres from ixBlue/Saint-Etienne Fibres composition and design focused on our application Known composition Possibility of customization High cost => quotation obtained: 5 EUR/m for P-doped and 12 EUR/m for PCe !!!

Conclusions & To-do List Equipment and fibres are ready for the PSB deployment at the end of EYETS and for starting the 1° measurement campaign in 2017 An additional cable with new/different fibres needs to be ordered Selecting the fibres is becoming urgent! Some have already been identified Fibres do not need to be characterized to be inserted in a cable => can be done at posteriori Control unit Urgent to buy a additional unit Decide the long term strategy

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