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)

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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

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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