Ingrid-Maria Gregor (University Wuppertal)
for the ATLAS collaboration
June 6th, 2000
Optical Links for the ATLAS SCT and Pixel Detector
International Workshop on Semiconductor Pixel Detectors for Particles and X-Rays
Genova, Italy June 2000
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Ingrid-Maria Gregor University of Wuppertal
Overview
ATLAS Inner Detector Optical Link Architecture System Tests Conclusion
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ATLAS Inner Detector
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Data Transfer
Control and clock information must be transferred from acquisition system to the silicon detectors
Hit data must be transferred from the modules to a remote acquisition system
use of copper links unfeasible large amount of dead material which would be introduced problems from cross-talk and ground loops
it is proposed to use custom optical links to transfer data to and from the detector modules (SCT and Pixel Detector)
5Pixel2000 Genova, Italy
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Special Requirements (1)
radiation hardness ionizing radiation : 100kGy (SCT) to 550kGy (Pixel
detector) 1 billion lung x-rays neutron radiation :
Si-devices: 1*1015 n(1MeV)/cm2
GaAs-devices: up to 6.4*1015 n(1MeV)/cm2
expected over the 10 year lifetime of ATLAS (1st layer)
6Pixel2000 Genova, Italy
Ingrid-Maria Gregor University of Wuppertal
Special Requirements (2)
non-magnetic to avoid perturbing the inner detector magnetic field
low mass additional interactions in non-instrumented
regions of the detector would compromise the quality of momentum measurements
particle conversion
reasonably low cost
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Read-Out Link Architecture
Vertical Cavity Surface Emitting Laser
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Timing Triggering and Control (TTC link)
VCSEL Driver BiPhase Mark Encoder driver chip for VCSEL on acquisition side (12 way) 40MHz-Clock and Commands on one link
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Ingrid-Maria Gregor University of Wuppertal
TTC Link
Digital Optical Receiver IC decodes the signals received by the PIN recovers commands and 40MHz-clock LVDS output
2 versions: bipolar (SCT) and CMOS (Pixel)
SCT redundancy system: TTC data can be taken from redundancy link from a neighbouring data
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Data Link
VCSEL Driver Chip LVDS input 40Mbit/s (SCT), 80Mbit/s (Pixel 1st and
2nd layer) or 160Mbit/s (B-layer) NRZ (20MHz = 40Mbit/s) 2 versions: bipolar (SCT) and CMOS
(Pixel) SCT: in the event of failure, the data can
be rerouted through the second link Pixel: one link for outer layers, two for B-
layer (160MBit/sec)
11Pixel2000 Genova, Italy
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Opto-Package Specs
Custom package made of material with low Z, non-magnetic, with 2 VCSELs and 1 PIN
Fibres attached without standard connector not larger than 5.5 mm x 5.5 mm x 1.6 mm package and including devices have to stand radiation
levels operation temperature during testing: -25oC to 40oC operation temperature during ATLAS: -25oC to 15oC
three different designs under survey
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Taiwan Opto-Package
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Taiwan Opto-Package
5.5 mm
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Taiwan Opto-Package
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Opto-Elbow (Pixel)
Module Pigtail
Opto Elbow
Bending Zone
Solder Connection Single Side
Glue Attachment & Wire Bonding
DORIC VDC Opto-Package
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Ingrid-Maria Gregor University of Wuppertal
Opto Package Support (SCT)
VDC (VCSEL Driver Chip)DORIC (Receiver Chip)
VCSEL/PIN Package
ZIF Connector
Kapton Cable
Opto Hybrid
Module Connector
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System Tests
Characteristics of opto-link for this system under test: Radiation and Annealing studies Lifetime studies Bit Error Rate Single Event Upsets
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Annealing Studies of VCSEL
00:00 24:00 48:00 72:00 96:000,0
0,2
0,4
0,6
0,8
1,0
Ave
rage
Rel
ativ
e Li
ght O
utpu
t (R
LO)
Annealing time [h]
RLO of VCSEL (group A) annealed at 10mA RLO of VCSEL (group A) annealed at 20mA RLO of VCSEL (group B) annealed at 10mARLO of VCSEL (group B) annealed at 20mA
Light Output before Irradiation
Light Output after IrradiationRLO =
Radiation levels:
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VCSEL tests
VCSELs were not powered during irradiation radiation induced damages can be annealed up to
90% over a period of days/weeks results suggest brief 20 mA current annealing
sessions following aging tests showed an expected lifetime
of a few hundred years (irradiated) further irradiation and lifetime tests are under way
(up to Pixel level of 6.4*1015 n(1MeV)/cm2)
20Pixel2000 Genova, Italy
Ingrid-Maria Gregor University of Wuppertal
Bit Error Rate (BER)
BER vs lightinput
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
80 100 120 140 160 180 200 220 240
Lightinput (mW)
BER
PIN-BIAS = 5V
PIN-BIAS = 0V
BER: good parameter to evaluate
the performance of the optolink
Good results with SCT link Pixel test under way
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Single Event Upsets
Single Event Upsets caused by a very high energy deposition in a small volume of electronics chips
most sensitive region: reverse-biased p/n junction where high electric field is very effective in collecting the charge by drift
PIN = reverse biased p/n junction 100m x 50m x 50m ! First SEU appearance : NPL neutron beam test with pions at PSI
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SEU at PSI
Sensitive power around 100W
for P>350W, BER <10-10s-1
discrepancy between counter and Al foil
repeat next week
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Conclusion
data transfer using optical links custom packaging developments for the 40 Mb/s
optical link show good physical results design of complete Pixel opto-link under way radiation induced damages can be annealed up to
90% over a period of days results suggest brief 20 mA current annealing
sessions SEU problems can be fixed by sending more light
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Ingrid-Maria Gregor University of Wuppertal
Conclusion
http://www.atlas.uni-wuppertal.de/ Optolink/Pix_Optolink.html