Radiation tests on optical fibres for the lhc machine
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Radiation Tests on optical fibres for the LHC machine . T. Wijnands , D. Ricci CERN EN department Fraunhofer INT. First radiation test on optical fibres. December 2002 : First radiation test on SM and MM fibres ~400 Gy total dose (SPS target area) RIA : a few dB/km @ 400 Gy

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Radiation Tests on optical fibres for the LHC machine

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Radiation Tests on optical fibres for the LHC machine

T. Wijnands, D. Ricci

CERN EN department

Fraunhofer INT


First radiation test on optical fibres

December 2002 :

First radiation test on SM and MM fibres

  • ~400 Gy total dose (SPS target area)

  • RIA : a few dB/km @ 400 Gy

  • Conclusion was : RIA is not an issue !


Total dose test with 60Co source

March 2005 :

Verification of attenuation data with 60Co source:

  • 1310 nm and 1550 nm

  • Ge-P doped a-SiO2 fibres from Draka NK Cables Ltd

    manufactured using the MCVD (Modified Chemical Vapour Deposition) process

    _Ge-doped a-SiO2 fibres from DrakaFibre Technology BV

    manufactured using the PCVD (Plasma Chemical Vapour Deposition) process


Radiation Induced attenuation

Ge-doped fibres

Dose rate : 1 kGy per hour


Radiation Induced attenuation

Ge-doped fibres

After annealing at room temperature


LHC cleaning sections

2005 : Difficult situation in the LHC

  • Many SM optical fibres are passing through LHC cleaning sections

  • Dose rate is ~10 kGy/year

  • Maximum attenuation (BPM/BLM system) 7 dB/km

  • For Ge-doped fibres 7dB/km RIA corresponds to 600 Gy !

  • LHC operational in 2007 !

Start of search for SM radiation hard optical fibres


LHC cleaning sections

2005 : Difficult situation for fibres in the LHC !

  • Many SM optical fibres are passing through LHC cleaning sections

  • Dose rate is ~10 kGy/year

  • Maximum attenuation (BPM/BLM system) 7 dB/km

  • For Ge-doped fibres 7dB/km RIA corresponds to 600 Gy !

  • LHC operational in 2007 !

Start of search for SM radiation hard optical fibres for LHC


T. Wijnands et al. TWEPP 2007 Prague


Lessons learned

  • RIA is caused by TID

  • Test results in SPS (complex radiation field) near identical to 60Co.

  • Production process is very special

  • Small manufacturing changes may cause large variations in RIA

  • QA is crucial for the series production and includes sample testing

  • QA is crucial when you test on RIA (procedure, test setup , samples)


M&O and new applications

  • How to address QA for small batches of radhardfibres ?

  • What fibres can be used for applications > 100 kGy ?

  • What if T = 5 Kelvin ?

  • What coating ?

  • How to achieve compatibility with blowing technique ?

  • Can we also find radhard MM fibres?

  • Can we use light at 850 nm ?


Radiation test of SM Optical Fibres

25 January 2010 :

3 random samples from LHC series production :

  • RRSMFB 110A

  • RRSMFB 630A

  • RRSMFB 380A

    one sample from the 3 was selected for the test

    11 February 2010 :

    Start of irradiation test up to 5 MGy:

  • 1310 nm and 1550 nm

  • Room temperature

  • Light power 10 mW

  • Dose rate 220 Gy/min

    4 March 2010 :

    End of first irradiation test


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