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 400 Gy – Conclusion was : RIA is not an issue !

Total dose test with 60 Co source March 2005 : Verification of attenuation data with 60 Co 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 Draka Fibre Technology BV manufactured using the PCVD (Plasma Chemical Vapour Deposition) process

Radiation Induced attenuation Dose rate : 1 kGy per hour Ge-doped fibres

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 60 Co. – 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)

How to address QA for small batches of radhard fibres ? 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 ? M&O and new applications

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  W – Dose rate 220 Gy/min 4 March 2010 : End of first irradiation test