High Fluence Irradiation Tests of Optical Link Components for Upgraded CMS at SLHC

1. First High Fluence Irradiation Tests of Optical Link Components for Upgraded CMS at SLHC M.Axer, S.Dris, K.Gill, R.Grabit, E.Noah, R.Macias-Jareno, J.Troska, and F.Vasey11th Workshop on Electronics for LHC and Future Experiments 13 September 2005  Heidelberg

2. Outline • Introduction Current Optical Links for the CMS Tracker Experimental Objectives • High Fluence Neutron Irradiation Test Devices Under Test Irradiation Facility Measured Parameters • Test Results Radiation Damage Thermal Behavior Streamlined Method • Summary & Conclusions Markus Axer

3. Optical Links for the CMS Tracker • During the first 10 years of LHC operation: • Worst case: operation at a distance of 22cm from the beam-axis in the forward region of the tracker • Expect ionizing radiation doses of up to 100kGy • Expect fluences of up to 2x1014 particles/cm2(dominated by ~200MeV pions) • Radiation damage on optical link components has been studied thoroughly using fluences in excess of 1014 particles/cm2 • Suitability for the CMS Tracker application in terms of radiation resistance and reliability has been validated Markus Axer

4. Experimental Objectives • In view of an upgraded LHC machine (‘Super-LHC’) with an increased luminosity of 1035cm-2s-1: • Expect a 10 times higher radiation level • CMS Tracker components will be exposed to ~2x1015p/cm2 (Ep~200MeV) in the worst-case  Accomplish a first high fluence irradiation test of some active optical link components in order to • Explore their suitability under much higher fluences than intended • Assess the possibility of re-using the devices (see also poster contribution of St. Dris: “Maximizing the Bandwidth Efficiency of the CMS Tracker Analog Optical Links”) • Start to evolve new validation and qualification procedures towards LHC/CMS upgrades • Gain some experience of high fluence testing in general Markus Axer

5. Devices Under Test • 5 current CMS Tracker laser transmitter: • Commercial off-the-shelf (COTS) device: Mitsubishi ML7CP8 • 1310nm InGaAsP/InP multi- quantum-well edge emitting laser • Fabry-Perot Type • Packaged and pigtailed by STMicroelectronics Digital Optohybrid used in the CMS Tracker laser transmitter pin photodiode • Also tested: • 2 high speed laser transmitter: Hitachi HL1359CP, InGaAsP/InP MQW, DFB Type • 6 CMS Tracker pin photodiodes: Fermionics FD80S8F, InGaAs/InP • 3 high speed pin photodiodes: Fermionics FD50S7F, InGaAs/InP Markus Axer

6. High Fluence Neutron Irradiation at UCL 50 MeVDeuterons Beryllium Target Neutrons • Universite Catholique de LouvainCentre de Recherches du Cyclotron, Belgium • 9Be (d,n) 10B • Average neutron energy: En=20,4 MeV Beryllium Target Devices Under Test • Devices placed very close to target: 5-15cm • Constant ambient temperature at the lasers using controllable ventilating system • Total fluence of 4x1015n/cm2(equivalent to ~2x1015p/cm2 wrt damage) reached in ~22hrs • ‘LHC fluence’ reached in ~2.5hrs • Lasers were connected both optically and electrically in order to measure the damage and annealing effects as well as the laser temperature in-situ Contact Karl.Gill@cern.ch for usage of the UCL irradiation facility Markus Axer

7. L-I Characteristic DL DI Eff=DL/DI Light-Current (L-I) characteristic of a non-irradiated laser at Tamb=20°C Thermal rollover Ith • Threshold current Ithlaser starts to emit coherent light • EfficiencyEffslope of L-I curve in linear part • Thermal rollovernon-linear part of L-I curve where non-radiative recombination mechanisms (Auger) become dominant due to internal temperature Markus Axer

8. Radiation Damage • In collisions with incident particles or recoiling atoms host atoms can be removed from their initial crystal lattice positions  displacement damage • Vacancy and interstitials related defects are created and introduce energy levels into the band-gap • Non-radiative recombination centers cause the carrier lifetime to decrease • As a consequence the threshold increases whereas the efficiency decreases proportional to fluence • Thus both parameters are adequate indicators for radiation damage Markus Axer

9. Wavelength Spectrum • The wavelength spectrum emitted by a laser diode is a perfect indicator of the device’s internal temperature – the junction temperature Tj • The wavelength spectrum is red-shifted when the device is heated by increasing the ambient temperature or the input power Typical wavelength spectrum of a Fabry-Perot type laser measured with an Optical Spectrum Analyzer Markus Axer

10. Results on Radiation Damage • Before irradiation Markus Axer

11. Results on Radiation Damage Markus Axer

12. Results on Radiation Damage Markus Axer

13. Results on Radiation Damage Markus Axer

14. Results on Radiation Damage • After ~2.5 hrs of irradiation a fluence of 4x1014 n/cm2 reached (‘LHC fluence‘) • Radiation damage in terms of threshold or efficiency is proportional to neutron fluence • Threshold increase of ~25mA • Efficiency loss of ~20% LHC Markus Axer

15. Results on Radiation Damage • After ~2.5 hrs of irradiation a fluence of 4x1014 n/cm2 reached (‘LHC fluence‘) • Radiation damage in terms of threshold or efficiency is proportional to neutron fluence LHC Markus Axer

16. Results on Radiation Damage • After ~2.5 hrs of irradiation a fluence of 4x1014 n/cm2 reached (‘LHC fluence‘) • Radiation damage in terms of threshold or efficiency is proportional to neutron fluence • Thermal rollover becomes visible LHC Markus Axer

17. Results on Radiation Damage • After ~2.5 hrs of irradiation a fluence of 4x1014 n/cm2 reached (‘LHC fluence‘) • Radiation damage in terms of threshold or efficiency is proportional to neutron fluence • Thermal rollover LHC Markus Axer

18. Results on Radiation Damage • After ~2.5 hrs of irradiation a fluence of 4x1014 n/cm2 reached (‘LHC fluence‘) • Radiation damage in terms of threshold or efficiency is proportional to neutron fluence • Thermal rollover • In excess of 3x1015 n/cm2the efficiency approaches zero LHC Markus Axer

19. Results on Radiation Damage • After ~2.5 hrs of irradiation a fluence of 4x1014 n/cm2 reached (‘LHC fluence‘) • Radiation damage in terms of threshold or efficiency is proportional to neutron fluence • Thermal rollover • In excess of 3x1015 n/cm2the efficiency approaches zero LHC Markus Axer

20. Results on Radiation Damage • After ~2.5 hrs of irradiation a fluence of 4x1014 n/cm2 reached (‘LHC fluence‘) • Radiation damage in terms of threshold or efficiency is proportional to neutron fluence • Thermal rollover • In excess of 3x1015 n/cm2the efficiency approaches zero • All lasers under test showed the same behavior LHC Markus Axer

21. Results on Radiation Damage • During irradiation Laser  LED behavior • After irradiation: beneficial annealing LED  Laser behavior Markus Axer

22. Thermal Effects during Irradiation • A parameter that describes the device’s efficiency to release heat generated inside the laser is called Thermal Resistance Rth Markus Axer

23. Thermal Effects during Irradiation • A parameter that describes the device’s efficiency to release heat generated inside the laser is called Thermal Resistance Rth • Dl/DTamb measured in an oven: Markus Axer

24. Thermal Effects during Irradiation • A parameter that describes the device’s efficiency to release heat generated inside the laser is called Thermal Resistance Rth • Dl/DTamb measured in an oven: • Dl/DPin monitored during irradiation: Markus Axer

25. Thermal Effects during Irradiation • A parameter that describes the device’s efficiency to release heat generated inside the laser is called Thermal Resistance Rth • Dl/DTamb measured in an oven: • Dl/DPin monitored during irradiation: Markus Axer

26. Thermal Effects during Irradiation • Rth allows the calculation of the actual laser temperature Tj at threshold during irradiation Markus Axer

27. Thermal Effects during Irradiation • Rth allows the calculation of the actual laser temperature Tj at threshold during irradiation • Tj can be used to correct the measured threshold current • Laser temperature contributes with up to ~40% to the threshold shift • Plateau is due to annealing which decreases the rate of damage Markus Axer

28. Qualitative Model • The observed effects are synergestic • Under the existing test conditions the combination of radiation damage and thermal effects ultimately determined the ‘lifetime’ of the lasers Markus Axer

29. A Streamlined Method • The combined results suggest that a streamlined method could be used for future radiation hardness validation tests such that • the radiation damage is measured at lower fluences only (easier and cheaper test) • a full thermal characterization of the device is done in parallel prediction Markus Axer

30. Summary & Conclusions • Good experience gained during the first high fluence neutron irradiation test • Radiation damage and thermal effects were studied on active optical link components (focused on current CMS TK laser transmitter) using neutron fluences of up to 4x1015n/cm2 at Tamb=20°C • Results: • Efficiency approaches zero at ~3x1015n/cm2 • Lasers show beneficial annealing (during and after irradiation) • Suitability for SLHC environment can be seen optimistically • Internal laser temperature is a key issue in terms of laser lifetime • Based on the results a streamlined method could be proposed for future radiation hardness validation tests such that • The radiation damage is measured at low fluences only • And a thorough thermal characterization is done in parallel • Further irradiation tests are certainly needed... Markus Axer

31. Additional Slides Markus Axer

32. L-I characteristics Markus Axer

33. Threshold Correction Markus Axer

34. Wafers Comparson: Threshold • 5 AVTs f = 4 to 61014n/cm2 time 6 – 7.5 hrs • To compare wafers, normalized results wrt 51014n/cm2 • Average damage ~24mA Markus Axer

35. Laser Damage Prediction in CMS Tracker • Based on damage factors and annealing rate at close to -10°C • Take worst-case • radius=22cm in Tracker • pion damage dominates • DIthr~6mA in 10 years • DE~5% in 10 years Ref: Gill et al, SPIE 2000 and 2002 Markus Axer

36. Damage Comparison • Relative damage factors: Valduc 0.8MeV n (=0.12) UCL 20MeV n (=0.53) PSI 200MeV p (=1) 60Co g (~0) Ref: Gill et al, SPIE 2000 and 2002 Markus Axer

37. Radiation Damage in Photodiodes • Current CMS Tracker photodiodes: • Continuation of the effects seen to date • Leakage current appears to be saturating • Responsivity is going to zero • No significant annealing • High speed devices: • Current CMSTracker and high speed devices behave similar Markus Axer

38. The Paoli Method Markus Axer

39. Spectral Behavior during Irradiation 55mA • The behavior of certain mode peaks is unique for all LDs: • “Slight” l red-shift with increasing fluence at the same input current level • “Large” l red-shift when increasing the input current 45mA 25mA 10mA  Popt is affected by I and by irradiation • Rs is constant during irradiation •  term is mainly affected by I • Ith increases during irradiation •  term is mainly affected by irradiation Markus Axer

40. CMS Tracker Analogue Optical Link Markus Axer

41. Radiation Environment LHC SLHC 1e16 1e15 1e14 1e13 1e14 Markus Axer