Slide 1 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Radiation tolerant fibres for LHC controls and communications  Jochen Kuhnhenn  Fraunhofer INT Appelsgarten 2 D Euskirchen Germany

Slide 2 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Outline  Introduction  Project overview: "Radiation tolerant fibres for LHC"  Results  Conclusions

Slide 3 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Introduction  Introduction  Motivation  The Fraunhofer Institute at a glance  Radiation effects on optical fibres  Project overview  Results  Conclusions

Slide 4 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Motivation  More than km of optical cables needed for LHC  Control and communication  Beam instrumentation  Advantages of optical communication  Extreme noise immunity and ground potential independence  Lower attenuation (no repeater needed)  Higher flexibility (additional links on demand without tunnel access)  In LHC cleaning insertions IR3 and IR7 high radiation levels expected from day 1  First tests of installed fibres led to concerns if continuous transmission will be possible (Wijnands et al.: LHC Project Note 351, Presentation at 4 th LHC radiation workshop)

Slide 5 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT The Fraunhofer INT  Experience of more than 30 years on effects of nuclear radiation on electronics and opto-electronics  The institute operates several irradiation facilities (Co-60, 14 MeV neutrons, flash X-Rays, access to 35 MeV protons)  Offering irradiation services to governmental, scientific, and industrial customers including planning and interpretation  Full range of measurement equipment for characterisation and analysis of radiation effects in electronics and opto-electronics  One focus: Radiation effects on optical fibres  Tested several fibres of all types and manufacturers  Close contacts to fibre manufacturers and research institutions

Slide 6 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Radiation effects on optical fibres  Ionising radiation changes every property of an optical fibre  Refractive index  Bandwidth  Mechanical properties (e.g., tensile strength)  Additional: Generation of luminescence light  These effects show up typically only at relatively high doses or dose rates  Most obvious and disturbing effect is the increase of attenuation

Slide 7 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Parameter dependencies of RIA  Manufacturing influences  Fibre type (Single mode, graded index, step index)  Doping of core, doping of cladding (for SM fibres)  Preform manufacturer and used processes  Core material manufacturer  OH Content  Cladding core diameter ratio (CCDR)  Coating material  Drawing conditions  Operation conditions  Wavelength  Light power  Launch conditions  Environment  Total dose  Dose rate  Annealing periods  Temperature

Slide 8 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT "Radiation tolerant fibres for LHC": Project overview  Introduction  Project overview  Aims  Approach  Experimental details  Results  Conclusions

Slide 9 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Project aims  Verification of previous irradiation tests of currently installed optical fibres by Draka  Full characterisation of radiation effects in used Ge-doped Draka fibre  Identification of optical fibres with better radiation resistance  Modelling of radiation induced loss at different dose rates

Slide 10 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Project steps  Acquisition of possible alternative optical fibres  Screening test of all samples under identical conditions  Fixed dose, dose rate, temperature, light power, wavelength  Detailed testing of current Draka fibre and best two candidates  Variation of dose rate & dose, wavelength, light power  Accelerated simulation of LHC radiation environment

Slide 11 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Experimental details  Screening tests  Dose rate: 0.22 Gy/s  Dose: Gy  Room temperature  Wavelength: 1310 nm  Light power: ~ 10 µW  Detailed tests  Dose rate: Gy / s  3.7 Gy / s  Dose: up to Gy  Wavelengths: 1310 & 1550 nm  Light power: up to 300 µW

Slide 12 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Results  Introduction  Project overview  Results  Identification of alternative products  Screening tests of candidates  Detailed testing of now used fibre and best candidates  Modelling of dose rate dependence  Conclusions

Slide 13 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Identification of other products  Fraunhofer INT contacted 10 manufacturers known for radiation resistant optical fibres  Of those 6 provided samples Draka developed new fibre: "Draka New" Heraeus Fujikura Corning Manufacturer X Manufacturer Y  Additional sample of current Ge-doped fibre "Draka #445755"

Slide 14 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Results of candidate screening test  Logarithmic scale  Linear scale

Slide 15 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Detailed tests of Draka #445755: Wavelength dependence

Slide 16 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Detailed tests of Draka #445755: Dose rate dependence

Slide 17 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Comparison of dose rate dependence of new fibres  Draka New  Fujikura Draka New better Fujikura better

Slide 18 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Radiation induced loss of used and new fibres: Summary  Results for currently installed Ge-doped fibre by Draka  It is one of the best tested fibres of this type  1310 nm has advantages for doses higher than 6000 Gy  Increased light power does not improve radiation resistance (not shown in slides)  Two new candidates characterised with focus on dose rate dependence  Both candidates show better radiation tolerance for higher doses Draka New better at least by a factor of 2 for highest doses Fujikura better above 10 Gy with best performance (by a factor of 10) between 100 and 1000 Gy

Slide 19 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT LHC operation conditions assumed for loss modelling  LHC Project Note 375  One LHC year: 140 days of physics  Assumptions “Nominal” physics Fill length + Turn around: hours 2.3×10 16 total beam loss per year in IR7 Dose in fibres ~ Gy per protons (private communication: Wijnands, Kurochkin)  Expected radiation environment for optical fibres in IR7  Maximum averaged dose per year: ~ Gy  Maximum mean dose rate: 2 mGy/s  Peak dose rates expected to be much higher

Slide 20 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Extrapolated losses for maximum mean LHC dose rate

Slide 21 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Accelerated simulation of LHC conditions  Acceleration by factor 10 for operation:  Irradiation for 2 hours at ~ 20 mG/s  Annealing for 1 hour  Repeating 10 times  Same dose per cycle (~ 150 Gy) as expected for LHC  Simulates nearly two weeks of LHC operation  Comparison of cyclic irradiation with results of continuous irradiation at corresponding mean dose rate

Slide 22 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Cyclic irradiation compared with continuous irradiation

Slide 23 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Cyclic irradiation compared with continuous irradiation

Slide 24 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Conclusions  Introduction  Project overview  Results  Conclusions

Slide 25 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Conclusions  Currently installed Ge-doped Draka fibre can be operated for extended time (If average mean dose rate scaling is appropriate)  Both new candidates show better radiation tolerance (Extend depending on dose range)  Cyclic irradiations with annealing periods do not lead to a attenuation increase as the corresponding continuous irradiation  Better understanding of realistic conditions at LHC needs time- dependent dose rate data and further investigations

Slide 26 5th LHC RADIATION WORKSHOP, CERN, , Jochen Kuhnhenn, Fraunhofer INT Thank you very much for your attention  I’m looking forward to your questions … Contact: Dr. Jochen Kuhnhenn Fraunhofer INT Appelgarten 2 D Eurkichen Germany Tel.: +49(2251)18200 Fax: +49(2251)