Radiation-Hard Optical Link for SLHC

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1 Radiation-Hard Optical Link for SLHC W. Fernando, K.K. Gan, A. Law, H.P. Kagan, R.D. Kass, A. Rau, S. Smith The Ohio State University M.R.M. Lebbai, P.L. Skubic University of Oklahoma B. Abi, F. Rizatdinova Oklahoma State University September 4, 2007 K.K. Gan TWEPP2007 1

2 Outline Introduction Bandwidth of micro twisted-pair cables Radiation hardness of PIN/VCSEL arrays Results on MT-style optical packages based on BeO Summary K.K. Gan TWEPP2007 2

3 ATLAS Pixel Opto-Link Architecture ATLAS is a detector studying pp collisions of 14 TeV at CERN pixel detector is innermost tracker detector upgrade planned for Super-LHC in 2015 micro twisted pairs decouple pixel and opto module simplify both design/production 8 m of rad-hard/low-bandwidth SIMM fiber fusion spliced to 70 m rad-tolerant/medium-bandwidth GRIN fiber upgrade based on current pixel link architecture to take advantage of R&D effort and production experience? K.K. Gan TWEPP2007 3

4 R&D Issues for SLHC bandwidth of ~ 1 Gb/s is needed can micro twisted pair transmit at this speed? can fusion spliced SIMM/GRIN fiber transmit at this speed? measured bandwidth ~ 2 Gb/s (see LECC06 talk) can PIN/VCSEL arrays survive SLHC radiation dosage? K.K. Gan TWEPP2007 4

5 Bandwidth of Micro Twisted Pairs Rise Time (20% - 80%) (ps) !m, 7.5!m Ins, 2 turns/cm 127!m, 9!m Ins, 2 turns/cm 127!m, 9!m Ins, 4 turns/cm 100!m, 12.5!m Ins, 4 turns/cm 100!m, 25!m Ins, 2 turns/cm (current pixel cable) 100!m, 25!m Ins, 4 turns/cm 127!m, 25!m Ins, 2 turns/cm Length (cm) current pixel cable with thick insulation is quite optimum! K.K. Gan TWEPP2007 5

6 Eye Diagrams 127 µm cable 140 cm 100 µm current pixel cable 140 cm 60 cm 640 Mb/s 1280 Mb/s transmission at 640 Mb/s is adequate transmission at 1280 Mb/s may be acceptable 127 µm cable is slightly better K.K. Gan TWEPP2007 6

7 Radiation Level at SLHC Optical link of current pixel detector is mounted on patch panels: much reduced radiation level: Si SLHC (5,000 fb -1 ): 2.5 x MeV n eq /cm x p/cm 2 or 114 Mrad for 24 GeV protons GaAs SLHC: 14 x MeV n eq /cm x p/cm 2 or 59 Mrad for 24 GeV protons above estimates include 50% safety margin K.K. Gan TWEPP2007 7

8 PIN Responsivity 10 8 Pre-irrad Post-irrad 6 Count Responsivity (A/W) Si PIN responsivity decreases by 65% after SLHC dosage completed irradiation of GaAs PIN from 3 vendors: Optowell, AOC, ULM responsivities will be measured next month K.K. Gan TWEPP2007 8

9 VCSEL LIV Characteristics 4000 OSU V Optowell Power (!W) Optowell Voltage (V) Current (ma) OSU V005 - ULM 5 Gb/s Pre-irrad 4000 OSU V006 - ULM 10 Gb/s 2.5 Power (!W) Current (ma) ULM 5G Voltage (V) K.K. Gan TWEPP Power (!W) Current (ma) ULM requires higher voltage to operate all arrays have very good optical power ULM 10G Voltage (V)

10 VCSEL LIV Characteristics Pre-irrad both arrays have very good optical power K.K. Gan TWEPP

11 VCSEL Power vs Dosage 2006: Two arrays each (2 x 7 channels) Optowell & ULM (10 Gb/s) might survive to SLHC dosage more VCSELs might survive with lower intensity/more annealing K.K. Gan TWEPP

12 VCSEL Power vs Dosage 1st irradiation period 2007 preliminary Two arrays each (2 x 7 channels) 2nd irradiation period Optowell & ULM (10 Gb/s) might survive to SLHC dosage K.K. Gan TWEPP

13 VCSEL Power vs Dosage 1st irradiation period 2007 preliminary Two arrays each (2 x 7 channels) 2nd irradiation period AOC (5 & 10 Gb/s) might survive to SLHC dosage need further analysis after radiation cool down K.K. Gan TWEPP

14 Opto-Pack Development current pixel detector uses Taiwan optical packages VCSEL mounted on PCB with poor heat conduction micro soldering of 250 µm leads is difficult Ohio State develops new opto-pack for SLHC uses BeO base with 3D traces for efficient heat removal wire bond to driver/receiver chip OSU Taiwan K.K. Gan TWEPP

15 Results on Opto-Packs 35 VCSEL & 6 PIN opto-packs have been fabricated all VCSEL opto-packs except one have good coupled power principle of new opto-pack has been demonstrated 1 cm MT ferrule VCSEL array K.K. Gan Ceramic guide pin TWEPP

16 Summary micro twisted-pair cable of current ATLAS pixel detector can be used for transmission up to 1 Gb/s fusion spliced SIMM/GRIN fiber can transmit up to 2 Gb/s Si PIN responsivity decreases by 65% after SLHC dosage VCSEL from 3 vendors might survive to SLHC dosage current opto-link architecture satisfies SLHC requirements compact MT-style opto-pack based on BeO has been developed K.K. Gan TWEPP

STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN ARRAYS

STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN ARRAYS K.K. GAN, W. FERNANDO, H.P. KAGAN, R.D. KASS, A. LAW, A. RAU, D.S. SMITH Department of Physics, The Ohio State University, Columbus, OH 43210, USA