Radiation-Hardness of VCSELs & PINs
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R. Kass ICTPP09
Radiation-Hardness of VCSELs & PINs
Richard KassThe Ohio State University
OUTLINEIntroduction/ATLAS pixel detector
Radiation Hardness of VCSELs Radiation Hardness of PINs
Summary
A. Adair, W. Fernando, K.K. Gan, H.P. Kagan, R.D. Kass, H. Merritt, J. Moore, A. Nagarkar, S. Smith, M. Strang
The Ohio State University
M.R.M. Lebbai, P.L. SkubicUniversity of Oklahoma
B. Abi, F. RizatdinovaOklahoma State University
R. Kass ICTPP09
The Current ATLAS Pixel Detector
A pixel module contains:1 sensor (2x6cm) ~40000 pixels
16 front end (FE) chips 2x8 array
Flex-hybrid1 module control chip (MCC)There are ~1744 modules
~1.85m
Present Pixel Detector:ATLAS’s Inner most charged particle tracker Measures (x,y,z) to ~30 mPixel detector is based on silicon Pixel size 50m by 400 m ~80 million pixelsRadiation hardness is an issue must last ~ 10 years
ATLAS: an LHC detector designed to study 14 TeV pp collisionsPixel detector is inner-most system -> Radiation damage is the issue
Detector upgrades planned: New Inner layer (“IBL”) & later a new pixel detector for Super-LHC
R. Kass ICTPP09
Present Pixel Opto-link ArchitectureCurrent optical link of pixel detector transmits signals at 80 Mb/sOpto-link separated from FE modules by ~1m
transmit control & data signals (LVDS) to/from modules on micro twisted pairs
Use PIN/VCSEL arrays
Use 8 m of rad-hard/low-bandwidth SIMM fiber fusionspliced to 70 m rad-tolerant/medium-bandwidth GRIN fiber Simplify opto-board and FE module production Sensitive optical components see lower radiation level than modules PIN/VCSEL arrays allow use of robust ribbon fiber
VCSEL: Vertical Cavity Surface Emitting Laser diodeVDC: VCSEL Driver CircuitPIN: PiN diodeDORIC: Digital Optical Receiver Integrated Circuit
optoboard holds VCSELs, VDCs, PINS
~80m
optoboard
~1m
R. Kass ICTPP09
Radiation Dosage at SLHC
VCSEL/PIN of current pixel detector are mountedon patch panel (PP0) instead of directly on the pixel module
much reduced radiation level compared with module
VCSEL/PIN for pixel detector at SLHC will be mounted further away from pixel module expected dosage at r = 37 cm for 3,000 fb-1 with 50% safety factor: silicon: 7.2 x 1014 1-MeV neq/cm2
GaAs: 2.8 x 1015 1-MeV neq/cm2
Assuming radiation damage scales with Non-Ionizing Energy Loss (NIEL)
R. Kass ICTPP09
Real Time Monitoring in T7 Beam Test
2009 Beam Tests used a simple system Real time monitoring of PIN current & optical power.
PIN diode arrays VCSEL arrays
VCSEL arrayslaser spot = beam spot Control Room
24 GeV proton beam
R. Kass ICTPP09
850 nm VCSEL Irradiation
2006-7: 12-channel VCSEL arrays were irradiated to SLHC dosageAOC 2.5 Gb/s (obsolete), 5 Gb/s, 10 Gb/sULM 5 Gb/s, 10 Gb/sOptowell 2.5 Gb/s
insufficient time for annealing during irradiation
2008:AOC 5 Gb/s, 10 Gb/sOptowell 2.5 Gb/s
2009:AOC 10 Gb/s goal: 20 arrays
actual: 6 arrays due to manufacturer problem
MPO connector
MPO adaptor
Opto-pack
R. Kass ICTPP09
AOC 10 Gb/s VCSEL (2008)
Optical power recovery by annealing is slowAlmost recover the initial power after extended annealingVCSEL produces more power at lower temperature
7.6 x 1015 1-MeV neq/cm2
irradiation
annealing
R. Kass ICTPP09
AOC 10 Gb/s VCSEL (2009)
irradiation
annealing
145 W
w/o long twisted/coiled fiber
Good optical power for 6 arrays irradiatedAwait return of arrays to OSU for annealing/characterization
need to irradiate a sample of 20 arrays in 2010
4.4 x 1015 1-MeV neq/cm2
R. Kass ICTPP09
Gb/s Responsivity (A/W)
GaAs (4.4 x 1015 1-MeV neq/cm2) Pre Post
ULM 4.25 0.50 0.09
AOC 5.0 0.60 0.13
Optowell 3.125 0.60 0.17
Hamamatsu G8921 2.5 0.50 0.28
Si (7.5 x 1014 1-MeV neq/cm2)
Taiwan 1.0 0.55 0.21
Hamamatsu S5973 1.0 0.47 0.31
Hamamatsu S9055 1.5/2.0 0.25 0.20
2008 PIN Irradiation
Irradiated 2 arrays or several single channel devices of each typeHamamatsu devices: low bandwidth but more radiation hardIrradiated 20 Optowell arrays in 2009
R. Kass ICTPP09
Responsivity doesn’t depend on bias voltage before irradiationCan increase responsivity with higher bias after radiation
Optowell
ULM
PIN Responsivity vs Bias Voltage
AOC
4.4 x 1015 1-MeV neq/cm2
Optowell
Pre-irrad
(2008)
R. Kass ICTPP09
PIN Responsivity vs Bias Voltage
Can fully recover pre-irradiation responsivity with large bias voltage Need to look at pulse shape at high bias voltage
Optowell
R. Kass ICTPP09
Eye Diagram at High Bias Voltage
Test limited to 1 Gb/s @ 40 V due to carrier board limitationEye diagram looks reasonableneed more detailed characterization
Optowell
R. Kass ICTPP09
Results on Optowell PIN Arrays
8.1 x 1015 1-MeV neq/cm2
20 Optowell PIN arrays irradiated August 2009Good responsivity after irradiation average responsivity after irradiation ~0.3 A/W
0
10
20
30
40
50
60
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Pre-IrradPost-Irrad
Cha
nnel
s
Responsivity (A/W)
10 arrays Analysis of additional ten arrayscomplicated by beam misalignment Need more detailed study, including eye diagram after cool down.
R. Kass ICTPP09
Summary
AOC 10 Gb/s arrays have good optical power after irradiation VCSEL produces more power as room temperature decreases Need to repeat irradiation with large sample in 2010
Hamamatsu PINs are slow but more radiation hard
Optowell PIN arrays have good responsivity after irradiation Can increase responsivity with higher bias voltage after radiation
Will irradiate a large sample of AOC PIN arrays in 2010 AOC plans to release high-speed PIN arrays in 2010
R. Kass ICTPP09
extra slides
R. Kass ICTPP09
Real Time Monitoring in T7 Beam Test
2006-8 test of opto-board system used loop-back setup
dataDORIC
clockPIN
VDCVCSEL
Opto-board
VDCVCSEL
bi-phase marked optical signal
decoded data
decoded clock
Signal routed back to opto-baord via test board
attached to 80-pin connector & test board
Bit error test setupat CERN’sT-7 beamline24 GeV protons
Compare transmitted and decoded dataMeasure minimum PIN current for no bit errors Measure optical power
In control room
25m optical
fiber cable
In beam
Two VCSEL arraysfrom same vendor per opto-board
Opto-Chip setup
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