optical links for the cms tracker at cern
DESCRIPTION
Optical links for the CMS Tracker at CERN. J. Troska (on behalf of Karl Gill) CERN EP Division. Outline. 1. Introduction Project LHC/CMS/Tracker/Optical Links Environment 2: Radiation damage testing at CERN Lasers fibres/connectors photodiodes System considerations 3: Summary - PowerPoint PPT PresentationTRANSCRIPT
Optical links for the CMS Tracker at CERN
J. Troska (on behalf of Karl Gill)
CERN EP Division
Outline
1. Introduction Project
LHC/CMS/Tracker/Optical Links Environment
2: Radiation damage testing at CERN Lasers fibres/connectors photodiodes System considerations
3: Summary
Copies of slides available: http://gill.home.cern.ch/gill/talks.html
LHC at CERN
CERN, Geneva
Large Hadron Collider
27 km circumference7 TeV proton beams
CMS
CMS Tracker development
Barrel layer prototype
Forward disk prototype
Layers of silicon microstrip detectors
~10 million detector channels
CMS Tracker analogue optical link
Transmitter - 1310nm InGaAsP EEL Fibres and connectors - Ge-doped SM fibre Receivers - InGaAs 12-way p-i-n plus analogue electronics - rad-hard deep sub-micron
Tracker radiation environment
Charged hadron fluence (/cm2 over ~10yrs)
high collision ratehigh energylarge number of tracks
radiation damage
lifetime >10 years temperature -10C
CMS Tracker readout and control links final system:
PLL Delay
MUX 2:1
Timing
APVamplifierspipelines
128:1 MUX
Detector Hybridprocessingbuffering
TTCRx
ADC
Rx Hybrid
FED
TTCRx
FEC
CCUCCU
CCU CCU
DCU
Control
processingbuffering
Front-End Back-End
TTC
DAQ
Analogue Readout50000 links @ 40MS/s
Digital Control2000 links @40MHz
Parts under test for radiation
damage
Tx Hybrid
Environments Optoelectronics already employed in variety of harsh
radiation environments e.g. civil nuclear and space applications
Totaldose(Gy)
Dose rate (Gy/hr)
1E-21E-2 1E+0 1E+2 1E+4 1E+6
1E+0
1E+2
1E+4
1E+6
1E+8Space (p,e)
Nuclear(, also n)CMS TK
CMS cavern
COTS issues
Extensive use of commercial off-the-shelf components (COTS) in CMS optical links
Benefit from latest industrial developments cheaper “reliable” tested devices
However COTS not made for CMS environment no guarantees of long-life inside CMS
validation testing of COTS mandatory before integration into CMS
COTS components for CMS Tracker links
Some examples:
single fibre and MU connector
1-way InGaAsP edge-emitting lasers on Si-submount with ceramic lid
12-way optical ribbon and MT-connector
96-way cable
Validation procedures for rad-resistance E.g. lasers and photodiodes
irradiation
n irradiation
irradiation
annealingageing
(in-system) lab tests
Highlighted:1999 Market survey
validation tests
(in-system) lab tests
Feedback test results into system specifications radiation damage effects can then be mitigated
Neutron tests at UC Louvain-La-Neuve
deut
eron
s
neutrons
Recent validation tests of laser diodes
~20MeV neutronsflux ~ 5x1010n/cm2/s
fluence ~ 5x1014n/cm2
(Similar to CMS Tracker10 year exposure)
neutrons
Samples stackedinside cold box (-10C)
Radiation test system
Test setup for in-situ measurements
In-situ measurements give powerful capability to extrapolate damage effects to other radiation environments e.g. CMS Tracker, if damage factors of different particles known
Similar test setup for p-i-n and fibre studies
MUX + DMM
I/O register
DAC
I generator
set V
Vout
Vin
photodetector
laserundertest
Mac + Labviewoptical fibre
current
Iout
signal
DataloggerUnit
Control roomIrradiationsource
neutron damage - Italtel/NEC lasersLight output vs current characteristics
before and after neutron irradiation
Fluence = 5x1014n/cm2
temperature =23C
600
500
400
300
200
100
0
optic
al p
ower
, L (
µW
)5040302010
current, I (mA)
LD1 pre-irrad LD2 pre-irrad LD1 post-irrad LD2 post-irrad
Damage effects consistent with build-up ofnon-radiative recombination centres in/around
active laser volume, causing a decrease ininjected charge carrier lifetimes
neutron damage - Italtel/NEC LDDamage vs fluence and time
annealing vs time
50
40
30
20
10
thre
shol
d cu
rren
t (m
A)
2.82.42.01.61.20.80.40.0
irradiation time (hrs)
4.03.02.01.00.0neutron fluence (1014n/cm2)
1.0
0.9
0.8
0.7
0.6
relative effiency, E/E
(0) I
thr LD1 Eff
LD1
Ithr LD2
EffLD2
1.0
0.9
0.8
0.7
0.6
0.5
frac
tion
rem
aini
ng d
amag
e
0.1 1 10annealing time (hrs)
Ithr
LD1
Ithr
LD2
eff LD1 eff LD2
Roughly linearincrease in damage
with fluence
Same annealing dynamics for threshold and
efficiency therefore indicate same underlying
physical damage mechanism
Different vendors compared
Ithr and Eff changes vs neutron fluence
4
2
0
86420neutron fluence, (1014n/cm2)
4
2
0
4
2
0
OptobahnIthr(0)~3.3mA
NortelIthr(0)~10.5mA
NEC (Italtel)Ithr(0)~12.2mA
Test B
Test B
Test B 1.0
0.8
0.6
86420
neutron fluence, (1014
n/cm2)
1.0
0.8
0.6
1.0
0.8
0.6
OptobahnE(0)~12µW/mA
NortelE(0)~8.5µW/mA
NEC (Italtel)E(0)~60µW/mA
Test B
Test B
Test B
similar effects in all 1310nm InGaAsP lasers
Radiation source comparison - Italtel/NEC laser For comparison with other sources:Normalize to fluence = 5x1014/cm2
in 96 hours irradiation
40
30
20
10
0
thre
shol
d in
crea
se,
I thr (
mA
)
543210
fluence, (1014/cm2 )
0.8MeV n0
~6MeV n0
330MeV +
24GeV p+
~20MeV n0
Damage factor ratios:0.8MeV n = 1
~6MeV n = 3.1~20MeV n = 4.9
330MeV pi = 11.524GeV p = 9.4
80
60
40
20
0
dam
age
(% 1
0yrs
ful
l lum
inos
ity)
1086420
LHC operating time (years)
LHC luminosity profile:
year 1: 10%year 2, 33%year 3, 66%
years 4-10, 100%
total damage annual components
Extend to 10 years, taking into account LHC luminosity profile
possible to estimate damage to laser threshold in CMS Tracker:
in worst case, at low radiiIthr = 14mA for Italtel/NEC lasers
Tests of fibre attenuation
Gamma damage (CMS-TK COTS single-mode fibres) at 1310nm
Tests of photodiodes - leakage
leakage current (InGaAs, 6MeV neutrons)
10-8
10-7
10-6
10-5
leak
age
curr
ent,
I leak
(A
)
0.1 1 10neutron fluence, (10
14n/cm
2)
all devices, -5V
Epitaxx (Italtel) Lucent Alcatel Epitaxx Nortel Fermionics
similar damage over many (similar) devices
Photodiodes - response
Photocurrent (InGaAs, 6MeV neutrons)
1.0
0.5
0.01050
neutron fluence, (1014
n/cm2)
1.0
0.5
0.0
1.0
0.5
0.0Fermionics
Epitaxx (FI)
Epitaxx (BI) /Italtel
Tests A and B
Test B
Test C
Significant differences in damage
depends mainly if front or back-illuminated
• front-illuminated better
Photodiode Single-event-upset Bit-error-rate for 80Mbit/s transmission with 59MeV protons in InGaAs p-i-n (D=80m) 10-90 angle, 1-100W optical power flux ~106/cm2/s (similar to that inside CMS Tracker)
10-12
10-10
10-8
10-6
10-4
10-2
100
Bit
-err
or-r
ate
-30 -25 -20 -15 -10
Optical power amplitude at PD (dBm)
p+ (beam off)
p+ (59MeV, 90°)
p+ (59MeV, 45°+)
p+ (59MeV, 30°+)
p+ (59MeV, 10°+) Ionization dominates for angles close
to 90 nuclear recoil dominates for smaller
angles BER inside CMS Tracker similar to
rate due to nuclear recoils should operate at ~100W opt. power
45° 10°90°beam
System considerations
Build in radiation damage compensation into optical link system
Lasers provide adjustable d.c. bias to track threshold increase provide variable gain to compensate for efficiency loss (and other gain
factors) Fibres and connectors
No significant damage Photodiodes
provide leakage current sink provide adjustable gain use sufficient optical power (~100W) to avoid significant SEU effects
Summary
CMS Tracker Optical links project 50000 analogue + 1000 digital links harsh radiation environment, 10 years at -10C COTS components
Extensive validation testing of radiation hardness necessary ionization damage (total dose) displacement damage (total fluence) and annealing reliability SEU
Accumulated knowledge of radiation damage effects compensation built into optical link system confidence of capacity to operate for 10 years inside CMS Tracker
http://cern.ch/cms-tk-opto/
Radiation environment in CMS
** high collision ratehigh energylarge number of tracks
radiation damage
require lifetime >10 years operating temperature -10C
fluences up to 2x1014cm-2
(dominated by charged pions)
total dose up to 150kGy
Single-mode optical fiber
Optical attenuator
Bit Error Rate testerOutput signal
Input signal
1310nm laser transmitter
Optical power-meter
Optical receiver circuit
PIN diode
Experimental setup for particle-induced BER
Incident beam
Annealing (current)
damage anneals faster at higher forward bias
0.90
0.80
0.70
0.60
0.50
rem
aini
ng d
amag
e,
I thr(
t)/
I thr(
)
1 10 100annealing time, t (hrs)
dc bias 0 60mA 80mA 100mA
“recombination enhanced annealing”
Reliability irradiated device lifetime > 10 years?? Ageing test at 80C
No additional degradation in irradiated lasers
acc. Factor ~400 relative to -10C operation
lifetime >>10years
60
50
40
30
20
10lase
r th
resh
old
curr
ent,
I thr (
mA
)
40003000200010000time in oven - 1st batch (hrs)
40003000200010000
time in oven - 2nd batch (hrs)
unirrad (batch 1) (10LD) neutron irrad (batch 1) (10 LD) neutron irrad (batch 2) (20 LD)
Fibre attenuation vs fluence
damage actually most likely due to gamma background
‘Neutron’ damage (CMS TK)
Damage picture
Defects introduced into band-gap by displacement damage non-radiative recombination at defects
competes with laser recombination
undoped InGaAsP MQW structure
stsp
nrdefect levels
n-type InP
p-type InP
Ev
Ec
Fibre annealing damage recovers after irradiation (e.g. gamma)
Damage therefore has dose-rate dependence
InGaAs p-i-n characteristics
Output current vs incident power
InGaAs p-i-n -5V
before/after 2x1014/cm2
200
150
100
50
0250200150100500
incident power, P in (µW)
pre-irr post-irr
Increase in Ileak
decrease in Iphoto
leakage current (InGaAs, different particles, 20C)
10-8
10-7
10-6
10-5
10-4
I leak
(A
)
1013
1014
1015
fluence (cm-2
)
330MeV 24GeV p ~6MeV n
all at -5V
higher energy , p more damaging than n
Different particles (leakage)
Different particles (response)
different particles:
1.0
0.8
0.6
0.4
0.2I PC /
I PC(0
) @
100
µW
1013
1014
1015
fluence (cm-2
)
330MeV 24Gev p ~6MeV n
all at -5V
higher energy , p more damaging than n
InGaAs p-i-n annealing After pion irradiation (room T, -5V)
1.0
0.9
0.8
rela
tive
I leak
ann
eal [
I leak
(t)/
I leak
()]
0.1 1 10 100Annealing time (hrs )
1.00
0.98
0.96
relative Iphoto anneal [Iphoto (t)/Iphoto ()]
after 330MeV leakage photocurrentall at -5V
Leakage anneals a little No annealing of response
InGaAs p-i-n reliability irradiated device lifetime > 10 years?? Ageing test at 80C
No additional degradation in irradiated p-i-n’s
lifetime >>10years
1.04
1.02
1.00
0.98
0.96
norm
aliz
ed p
hoto
curr
ent,
I pc(
t)/I p
c(0)
40003000200010000
time in oven - 1st group (hrs)
40003000200010000
time in oven - 2nd group (hrs)
unirrad control (group 1) irrad (group 1) irrad (group 2)
PD SEU
photodiodes sensitive to SEU
strong dependence upon particle type and angle
