R. KassIEEE05/Puerto Rico N37-3 1 Radiation-Hard Optical Link for the ATLAS Pixel Detector Richard...
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Transcript of R. KassIEEE05/Puerto Rico N37-3 1 Radiation-Hard Optical Link for the ATLAS Pixel Detector Richard...
R. Kass IEEE05/Puerto Rico N37-3 1
Radiation-Hard Optical Link for the ATLAS Pixel Detector
Richard Kass
The Ohio State University
W. Fernando, K.K. Gan, P. D. Jackson, M. Johnson, H. Kagan, R. Kass, A. Rahimi, C. Rush, S. Smith, R. Ter-Antonian
The Ohio State University
P. Buchholz, M. Holder, A. Roggenbuck, P. Schade, M. Ziolkowski
Universitaet Siegen, Germany
OUTLINEIntroduction
Proton irradiation results
Opto-board production
Summary
R. Kass IEEE05/Puerto Rico N37-3 2
The ATLAS Pixel Detector
• Inner most charged particle tracking• Pixel size 50m by 400 m• ~100 million pixels• Barrel layers at r = 5.1 - 12.3 cm• Disks at z = 50 - 65 cm• Dosage after 10 years:
– optical link 17 Mrad or 3.7 x 1014 1-MeV neq/cm2
disks
barrel layers
~380mm
~1850mm
R. Kass IEEE05/Puerto Rico N37-3 3
ATLAS Pixel Opto-link
VCSEL: Vertical Cavity Surface Emitting Laser diodeVDC: VCSEL Driver Circuit
PIN: PiN diodeDORIC: Digital Optical Receiver Integrated Circuit
Opto-board: Holds VDCs, DORICs, PINs, VCSELs Uses BeO as substrate
R. Kass IEEE05/Puerto Rico N37-3 4
Convert LVDS input signal into single-ended signal appropriate to drive the VCSEL diode
Output (bright) current: 0 to 20 mA, controlled by externally controllable current (Iset)
Standing (dim) current: ~ 1 mA for fast off-to-on switching of VCSEL
Rise & fall times: 1 ns nominal (40 MHz signals)
Duty cycle: (50 ± 4)%
“On” voltage of VCSEL: up to 2.3 V at 20 mA for 2.5 V supply
Constant current consumption balanced between ON and OFF state
Use IBM 0.25 m CMOS for radiation hardness
Use TRUELIGHT “high power oxide” common cathode VCSEL arrays
VCSEL Driver Circuit Specs
R. Kass IEEE05/Puerto Rico N37-3 5
Decode Bi-Phase Mark encoded (BPM) clock and command signals from PIN diode
Input signal size:
40 A - 1000 A
Extract 40 MHz clock
Duty cycle: (50 ± 4)%
Total timing error: < 1ns
Bit Error Rate (BER): < 10-11 at end of life Use Truelight common cathode PIN array
Use IBM 0.25 CMOS for radiation hardness
Digital Optical Receiver IC Specs
40MHzclock
Command
BPM
R. Kass IEEE05/Puerto Rico N37-3 6
The Opto-boardOptical signal electrical signal conversion occurs here
Contains 7 optical links, each link serving one Pixel module
Fabricated in 2 flavors– Layer B: for inner barrel, two data link per module for high occupancy – Layer D: for outer barrel and disks
Fabricated with BeO for heat management– initial prototypes with FR4 for fast turn around and cost saving
Need:44 B boards226 D boards
Opto-pack
Housing
Pin array
DORIC
VCSEL array
VDC
2cm
R. Kass IEEE05/Puerto Rico N37-3 7
Opto-board Performance & Status Detailed measurements are done on all critical electrical and optical
parameters to check performance/quality– LVDS rise/fall times, jitter…,
– Optical power, optical rise/fall times, duty cycle…
– The opto-boards meet or exceed all the pixel detector requirements
spec.
Optical power @ 10 mA
significantly > 500W spec
Optical power
spec.
Minimum PIN current for No BIT Errors
Minimum PIN current for no BIT
errors significantly < 40A spec
R. Kass IEEE05/Puerto Rico N37-3 8
Radiation Hardness Measurements
• Important to measure/certify radiation hardness of ASICs and opto-board and its components:– VCSEL and PIN arrays– VDC and DORIC chips– Encapsulant, fibers, glues, etc.
• Use CERN’s T7 beam (24 GeV Proton) for radiation hardness studies– “Cold box” setup: electrical testing of DORIC and VDC
Exposed up to 62 Mrad
– Shuttle setup: testing of optical links on opto-boards using DORIC and VDC Can be moved in and out of beam remotely for VCSEL
annealing Exposed up to 32 Mrad
R. Kass IEEE05/Puerto Rico N37-3 9
Real Time Monitoring in Beam TestReal time testing of opto-board system using 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
Bit error test board
Compare transmitted and decoded data measure minimum PIN current for no bit errors
Measure optical power
In control room
25 meter optical fiber cable
In beam
R. Kass IEEE05/Puerto Rico N37-3 10
PIN Current Threshold vs Dosage
PIN current thresholds for no bit errors remain constant
spec
24 GeV protons @ CERN
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Optical Power vs. Dosage
• Irradiate ~5 Mrad/day (10 hours) with annealing rest of the day• Optical power decreases with dosage as expected due to VCSELs• Limited annealing recovers some lost power• Still acceptable power after 30 Mrad
Spec
R. Kass IEEE05/Puerto Rico N37-3 12
Opto-board Production Challenges
Rigorous QA procedure:72 hours of burn-in at 50oC18 hours of 10 thermal cycles between -25oC and 50oC8 hours of optical and electrical measurements
Use 2 ovens and 2 environmental chambers
Implemented an “early shift” to extend the work day But no shifts on weekends.Aggressive goals:produce 10 boards/weekcomplete production in early October 2005
R. Kass IEEE05/Puerto Rico N37-3 13
Initial plan was not to test chips before mountingon opto-board due to high yield during pre-production
A bunch of produced boards drew excessive currentthermal imaging showed power to ground shorts
test all chips before mounting on opto-boards Chip yield turned out to be ~98%
Initial Production Problem
VDC DORIC
R. Kass IEEE05/Puerto Rico N37-3 14
0
40
80
120
160
200
240
280
2/253/25
4/225/20
6/177/15
8/12 9/910/7
Date
Bo
ard
0 4 8 12 16 20 24 28 32
Week
TotalTotal FailedTotal (Predicted)
Opto-board Production Status
Relatively smooth productionOpto-board yield ~ 93%
Production finished at OSU
80 MHzopto-boards
160 MHzopto-boards
Recovered 18 opto-boards by stacking new chips on top of bad chipsThese re-worked boards passed the standard rigorous QA procedureWill use these boards as spares.
R. Kass IEEE05/Puerto Rico N37-3 15
Summary
Opto-boards of ATLAS pixel detector satisfy design spec. and radiation hardness requirement:
low PIN current thresholds for no bit errorsexcellent optical power
radiation hard up to ~ 30 Mrad
Simple & modular design allows smooth productionopto-board production completed in seven months!
For More Details see: ATLAS PIXEL OPTO-ELECTRONICS, K. E. Arms et al., Apr 2005. Submitted to NIM, e-Print Archive: physics/0504142
R. Kass IEEE05/Puerto Rico N37-3 16
Backup Slides
R. Kass N37-3 17
Setup for Irradiation in Shuttle at CERN
Opto-boards
Rad hard optical fibers
25 meter optical fiber
Shuttle test electronics prior to shipping to CERN
Remotely moves in/out of beam
OSUOSU
CERN T7 CERN T7
R. Kass IEEE05/Puerto Rico N37-3 18
Proton Induced Bit Errors in PIN
Bit error rate decreases with PIN current as expected
bit error rate ~ 3 x 10-10 at 100 A (1.4 errors/minute)
DORIC spec: 10-11
Convert observed bit errors into bit error rate at opto-link location:
1.00E-11
1.00E-10
1.00E-09
1.00E-08
1.00E-07
0 100 200 300 400 500 600
IPIN (A)S
EU (c
m2 )
SE
U
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
0 100 200 300 400 500 600
IPIN (A)
BE
R