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
2017

•
PSB Installation to be
completed during
EYETS
2018
•
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?
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
2019
2020
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 limitations...
... on the fibre
Some promising results!
 Identification/localisation of dose
deposition events in a mixedradiation environment
 Dose resolution: ~ 10 Gy -15
Gy
 Spatial resolution: 1 m
•
Early saturation of tested fibre ~ 15 kGy
• Small dose rate dependency
Probably Ge+P => need P-doped!
Current Status – Distributed Radiation
Measurements
Some limitations...
... on the OTDR
Some promising results!
http://www.exfo.com/fr/produits/tests-terrain/bu6-ecosysteme-ftb/plateformes/ftb-500
 Identification/localisation of dose
deposition events in a mixedradiation environment
 Dose resolution: ~ 10 Gy -15
Gy
 Spatial resolution: 1 m
•
Limited dynamic range
•
Limited choice of wavelengths
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 Gedoped, + 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
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!
[email protected]