1. K. Gill, G. Cervelli, R. Grabit, F. Jensen, and F. Vasey. CERN, Geneva
Radiation damage and annealing in 1310nm InGaAsP/InP lasers for the CMS Tracker
K. Gill, G. Cervelli, R. Grabit, F. Jensen, and F. Vasey.
CERN, Geneva
August 2000

2. Background CMS Tracker readout and control project
Complex system with >50000 optical links
Harsh radiation environment
Extensive use of commercial off-the-shelf components (COTS)
Part-of series of on-going validation tests required before components integrated into final system
Previous tests reported at SPIE and RADECS

3. CMS Tracker optical link technology
lasers single-mode fibre + array connectors photodiodes
Transmitter nm InGaAsP edge-emitter
Fibres and connectors - single-mode Ge-doped fibre
Receivers - InGaAs p-i-n photodiode
Electronics - rad-hardened 0.25mm in radiation zones
COTS issues:
radiation damage: up to 1014particles/cm kGy
reliability: 10 year lifetime in radiation environment
Add figure
re-emphasise
widespread use in LHC
Tx, fibres, connectors exposed in readout links
all types of element exposed in control links

4. CMS Experiment

5. CMS Tracker radiation environment
Numbers come from:
Show Mika’s plots (Ref)
show fig for other environments, put LHC in context
space:
- optocouplers
- data bus (lightweight, low power fibre optics)
nuclear:
- sensors, fibroscopy
- diagnostics
charged hadrons (p, p, K)
(courtesy M. Huhtinen, CERN)

6. CMS Tracker readout and control links
Analogue Readout
MS/s
FED
Detector Hybrid
Tx Hybrid 96
Rx Hybrid
processing
MUX A
APV 4
buffering
2:1
amplifiers D
DAQ 12 12
pipelines C
128:1 MUX
Timing
PLL Delay
DCU
TTCRx
TTC
Digital Control
2000
FEC
Control 4 64
TTCRx
CCU
CCU 8
processing
buffering
CCU
CCU
Front-End
Back-End

7. System specifications
Analogue readout links
Last 2 columns filled in for each device type after testing

8. Objectives Compare damage from different particles
0.8MeV n and 6MeV n, 330MeV p, 24GeV p, 60Co g
Measure annealing characteristics
Temperature and current dependence
Make prediction for damage expected in CMS tracker
10 years at -10°C, including LHC luminosity profile

9. Experiment
Devices
Italtel/NEC 1310nm edge-emitting InGaAsP/InP MQW lasers
mounted on Si-submounts
compact mini-DIL packages, single-mode fiber pigtails
no other components in the package, e.g. lenses
Pre-irradiation characteristics at 20°C :
Laser threshold currents 8-13mA
Output efficiencies (out of the fibre) 30-70mW/mA
This type of device previously studied
6MeV n, 330MeV p, 24GeV p, 60Co g

10. DCPBH-MQW lasers double-channel-planar-buried-heterostructure laser
Emphasise similarities and differences with LED’s

11. Test Procedures
Test A: Irradiate 0.8MeV n - compare damage with other particles
4 lasers, irrad room T, biased 5-10mA above threshold, 1015n/cm2 in 6.5 hrs.
Anneal at room T, biased 5-10mA above threshold for 115 hrs
Test B: Irradiate 0.8MeV n - anneal at different T
12 lasers, cooled -13°C, unbiased, 1015n/cm2 in 6.3 hrs.
Anneal in groups of 3 at 20, 40, 60, 80°C for 300 hrs.
Test C: Irradiate 0.8MeV n - anneal at different bias currents
8 lasers, irrad room T, unbiased, 1015n/cm2 in 6.5 hrs.
Anneal in groups of 2 at 0, 40, 60, 80mA bias for 115 hrs.

12. Test setup for in-situ measurement of radiation damage and annealing

13. Test A - 0.8MeV irradiation at room T
Damage approximately linear with fluence

14. Test A - Comparison with other particles
Data averaged over
devices then normalized
to 96 hour irradiation
with 5x1014particles/cm2.
Relative damage factors for 0.8MeV n with respect to ~6MeVn (1/3.1), 330MeV p (1/11.4), 24GeV p (1/8.4).

15. Test B - cooled irradiation
Irradiation fluence
1015 (0.8MeV n)/cm2
Test made at -10°C, then devices stored at -35°C

16. Test B - Annealing versus temperature
Devices split into
4 groups of 3 and
annealing at different
temperatures.
Threshold damage
assumed to be
proportional to number
of defects
Annealing generally linear with log (time)

17. Test C - Annealing versus current
Irradiation to 1015n/cm2
at room T, unbiased,
then anneal in 4 groups of 2
at different bias currents
Enhancement caused by:
(i) ‘recombination enhanced
annealing’ (?)
- supposed to be unlikely in
InGaAsP/InP
(ii) thermal acceleration due
to power dissipation. At 80mA
DTjunction ~ 8C.
Up to factor 10 enhancement in terms of annealing time

18. Annealing model
Assume 1st order (exponential) annealing obeying Arrhenius law:
remaining fraction of defects:
where
For defects with a uniform distribution of activation energies r = N/(tmax-tmin), the annealing is linear with log (time)

19. Activation energy spectrum
Data points for each group of 3 devices averaged.
Fit annealing model
to Test B data.
Activation energy spectrum for best fit is 0.66<Ea<1.76eV

20. Damage prediction in 1yr in CMS tracker
Use model to predict annealing of defects at -10°C over 1 LHC year
LHC/CMS running
LHC shutdown
damage + annealing
annealing
32% of total defects introduced during 1 year are annealed

21. Damage prediction 10yrs in CMS tracker
Extend to 10 years, taking into account LHC luminosity profile
Based on damage of 0.8MeV n at -10C (Test B) and relative damage factors (Test A), possible to estimate damage to laser threshold in CMS Tracker:
in worst case, at low radii (and no bias-enhancement included),
DIthr = 14mA

22. Conclusions ‘Calibrated’ damage from 0.8MeV neutrons
relative to 6MeV n, 330MeV p, 24GeV p
Determined annealing dependence
temperature and forward bias current
Constructed a model to describe the annealing v T
uniform distribution of activation energy 0.66<Ea<1.76eV
Based on data, applied model to CMS Tracker to predict laser threshold damage
In the worst case, at low radii: DIthr = 14mA
Further work:
extension of the study to include lasers from other manufacturers.