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

2. 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

3. 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

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

5. 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

6. 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:

7. 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

8. Current Status – Distributed Radiation Measurements
Some promising results!
Some limitations...
... on the OTDR
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

9. 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 1064 nm in double-end configuration on radiation tolerant fibre

10. 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
Post LS2, LINAC4 => reaching 2 GeV!

11. 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

12. 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.

13. 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

14. 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

15. 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

16. 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)
...

17. 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

18. 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

19. 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?

20. 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 !!!

21. 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

22. Many thanks for your attention!