1. ATLAS Tracker Upgrade Liverpool December '06
SLHC Optoelectronics
Readout architectures
Technologies for TX
High speed multiplexing
Packaging
Radiation hardness and reliability testing
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

2. Architecture (1) Low speed links
Like current SCT: 2 data links/module (redundancy)
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

3. Architecture (2) High Speed Links
High speed MUX at end of supermodule.
Modules
Data Concentrator 1
Data Concentrator 8
MUX LD
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

4. Architecture for Pixels
MCC reads out n pixel chips. For SLHC, pixel chip size similar  occupancies x10  data transmission rates x10.
Pixels need 1-2 Gbits/s.
Question: can we have a common architecture for pixels and strips?
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

5. ATLAS Tracker Upgrade Liverpool December '06
Cost Estimates (1)
Assume Strawman layout for strips
21824 modules barrel modules disks
Low speed links: scale based on actual costs of SCT links + input from S-C Lee on commercial costs for opto-packages.
Total for strips = 32.7 MCHF (components only).
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

6. ATLAS Tracker Upgrade Liverpool December '06
Costs (2)
High speed links
Multiplex 30 modules  one fibre. Data rate ~3 GBits/s.
Scale costs from actual costs of LHCb GOL/VCSEL readout at 1.6 GBits/s. Larger uncertainties here. No redundancy in this calculation.
Estimated total cost for strips ~ 2 MCHF.
This estimate is approximate but conclusion  High speed links costs << low speed links. Francois Vasey “you have to fill the bandwidth of the fibre to be cost effective”.
Note a mixed solution with low speed fibres along supermodule and multiplexing to high speed links at the end of a stave would also be very expensive (only ~ 30% of the cost is for fibre).
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

7. Advantages Low Speed Links
Grounding: separate ground for each module but
have to join grounds for serial powering
ATLAS SCT had common grounds for larger number of modules (40 or 52) in End caps with no significant change in noise (TTC Redundancy interlinks s/c DGND).
For barrel SCT had 100 W redundancy links between DGND for neighboring modules in loop of 12 modules. No increase in noise seen.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

8. Disadvantages Low Speed Links
Cost much higher!
Packaging more difficult (space constraints more severe)
Single source for rad-hard SIMM fibre; might not be available for SLHC.
Fragile fibres on detector are not good (had many fibre breakages, some not repairable).
After mounting on detector, failures could not be replaced ( failures 4 or 5 years before start of operation were not recoverable).
Mounting is very difficult, time consuming  labour costs high.
Needs new chip set and we have nobody to work on it
Nobody interested in links to work on this option.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

9. ATLAS Tracker Upgrade Liverpool December '06
Low vs High Speed Links
Low speed versus high speed affects everything in system:
Fibres, transmitters, packaging  affects supermodule engineering.
We won’t make much progress until we make a decision.
My suggestion:
Adopt high speed links as baseline.
Low speed links as fall back if we can’t solve noise problems for modules.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

10. ATLAS Tracker Upgrade Liverpool December '06
Technologies
850 nm (ATLAS) + SIMM/GRIN fibre.
nm (CMS) + SM fibre.
nm (new) + SM fibre.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

11. ATLAS Tracker Upgrade Liverpool December '06
850 nm (1)
Advantages:
Very radiation hard, very small threshold shifts at SLHC fluences ( next transparencies)
Easy to couple into MM fibres.
Disadvantages
Needs custom packaging a la SCT/Pixel.
Bandwidth of SIMM fibre too low and GRIN fibre not radiation hard enough  mixed SIMM/GRIN fibre.
Needs custom fibres  concerns on cost and availability.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

12. Radiation Hardness VCSELs
See talk by Issever at LECC
No significant change in slope efficiencies up to SLHC fluence
Small threshold shifts  transparency
But some channels became sick after 15 mA. Not understood  needs further studies…
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

13. Results – Threshold Shift (After-Before)
10 10mA annealed and 5 15mA annealed
ΔThreshold [mA]
LHC, 20mA, proton implant
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

14. ATLAS Tracker Upgrade Liverpool December '06
850 nm (2)
Fibre Bandwidth
Very radiation hard SIMM fibre has low bandwidth > ~50 MHz km
Radiation tolerant GRIN fibre has higher bandwidth MHz km.
Splice 8m of SIMM fibre to ~ 80m GRIN fibre (as done for current Pixel readout).
Could operate up to ~ 5 Gbits/s.
Demonstration of Bandwidth
Tests by KK Gan (OSU) See talk at LECC
Scope photos of eye diagrams at 2 Gbits/s  transparency
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

15. ATLAS Tracker Upgrade Liverpool December '06
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

16. ATLAS Tracker Upgrade Liverpool December '06
EELs
Advantages
Couple to SM fibre at 1310 nm  choice of commercial fibres that are sufficiently radiation hard and very high bandwidth.
Can survive SLHC fluences.
Disadvantages
Higher thresholds than VCSELs and larger threshold shifts with radiation.
More difficult to couple to fibre but can be done by telecoms companies (as for current CMS).
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

17. ATLAS Tracker Upgrade Liverpool December '06
Radiation damage EELs
Threshold shift for SLHC worst case p cm2 is ~105 mA.
70% of damage will be annealed during operation
Threshold before irradiation ~ 4 mA.  after full SLHC fluence threshold ~ 36 mA (high!).
300 MeV/c p
K. Gill, SPIE 2002.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

18. ATLAS Tracker Upgrade Liverpool December '06
1310
Advantages
Best of both worlds. High bandwidth, availability of several sources of commercial radiation hard fibre nm expected to be very radiation hard.
Disadvantages
New technology  concern about availability.
Need to verify radiation hardness and reliability. Major effort in conjunction with CMS.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

19. High Speed Multiplexing
Current technology: GOL on 0.25 mm CMOS. Operates at 1.6 GBits/s . Radiation hard.
Should be possible to go faster with 0.13 or 0.09 mm.
CERN project aims to develop MUX ASIC.
SMU also developing MUX as part of LOC.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

20. ATLAS Tracker Upgrade Liverpool December '06
CERN VBDL Proposal
Versatile bi-directional links for ATLAS & CMS
Use for data, TTC and experimental control.
Following transparencies from P. Morerira, LECC 2006 talk
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

21. Transceiver Module GBT
MCM containing the ASIC, optoelectronic components and optical and electrical connectors.
Common definition
O/E
DAQ
Timing
Trigger
Experiment Control
GBT
E/O
Configurable to multiple optical networks (user driven)
Multi-protocol ASIC
Qualified optoelectronic components
(COTS)

22. Limiting Amplifier Specifications: Data rate: 3.60 Gbit/s
Gain: > 55 dB
Bandwidth > 2.52 GHz
Equivalent input noise: < 1 mV
Minimum input signal (differential): 10 mV
Maximum input signal (differential): 600 mV

23. Limiting Amplifier Offset Cancellation Bias Gain Cell Gain Cell Gain
Output Buffer
Size: 194 mm × 194 mm

24. Limiting Amplifier
3.35 Gbit/s
1 Gbit/s

25. CERN VBDL Summary (1) Versatile Link solution for:
Timing Trigger Links;
Data Acquisition Links;
Experiment Control Links.
The system allows flexible link topologies:
Bi-directional
Uni-directional
Point-to-Point
Point-to-Multipoint

26. CERN VBDL Summary (2)
Specifications and Interfaces are still evolving for which we need the feedback of the potential users
Some universal building blocks have already been prototyped:
Laser driver
Encoder/decoder: Line code and FEC
Limiting amplifier
The Versatile Bi-Directional Link project has been proposed by the Microelectronics group as a CERN common development.

27. ATLAS Tracker Upgrade Liverpool December '06
LOC
LOC being developed by SMU for SLHC
Integrate electronics and laser/PIN on chip using SOS technology  see talk by Jingbo Ye at this workshop.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

28. Link-on-Chip Architecture
Flip-chip
bonding
PLL and
clock generator
REFclock
encoder
Laser
Laser
Driver
serializer
Parallel
Data TX
transmitter Module
Optical
data
Receiver Module
Parallel Data
Photonic
Flip-chip
bonding
Decoder
De-
serializer
TIA/LA
PIN
REFclock
Clock/Data
recovery
Improve performance
No off-chip high speed lines
Flip-chip bonding reduces capacitance and inductance
Reduce power consumption
No 50-Ohm transmission lines between chips
Designed and Implemented in Silicon-on-Sapphire technology
Targeting speed:>2.5Gbps

29. Flipped OE devices on SoS substrate
flip chip attachment
UTSi integrated photo detector
UTSi integrated circuitry
VCSEL driver circuitry
receiver circuitry
quad VCSEL array
quad PIN array
active CMOS layer
200 um
transparent sapphire substrate
(UTSi)
MMF ribbon fiber
Flip-chip bonding of OE devices to CMOS on sapphire
No wire-bonds – package performance scales to higher data rates
Rugged and compact package
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

30. Transceiver IC with OE Devices and Link Performance
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06
Transceiver link eye at 3.2Gbps
at 2.0Gbps

31. ATLAS Tracker Upgrade Liverpool December '06
Packaging
Non trivial because must be radiation hard, non-magnetic, low mass, low Z material and fit in available space
Full custom packaging. Eg SCT opto-package or Pixel MT coupled arrays
Find Telecoms company package that is compatible with our requirements (CMS)
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

32. ATLAS Tracker Upgrade Liverpool December '06
Custom Packaging - SCT
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

33. ATLAS Tracker Upgrade Liverpool December '06
Used for Pixel on-detector and SCT/Pixel off-detector BOC
12 way array with MT guide pins for coupling to 12 way ribbon fibre
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

34. ATLAS Tracker Upgrade Liverpool December '06
Telecoms Packaging
CMS Analogue Opto Hybrid (AOH)
3 channels laser drivers, lasers and fibres
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

35. CMS Laser Sub-Mount Compact: 4.5 * 4 * 1.3 mm3 Fibre ends gold plated
Active alignment: resistor pads used to solder fibre in location. Glue only for strain relief of fibre
Radiation hard by design
Removed for CMS (save $)

36. ATLAS Tracker Upgrade Liverpool December '06
Pixel Links
Consider option to keep similar architecture
Number of links would be similar to current Pixel system and increase in luminosity  10 times higher data rate Need ~ 1 Gbit/s
Develop similar architecture chips to current DORIC and VDC in 0.13 mm
See talk by K.K. Gan at this workshop
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

37. ATLAS Tracker Upgrade Liverpool December '06
Common ATLAS/CMS WGs
Theme a- Lessons learned and to be learned.
Collect info on successes and mistakes of the groups involved in the present detectors. Follow up on the technology choices made over 10 years ago. Produce a transparent account of the costs incurred. Create a repository for all publications. Monitor and follow up the performance and ageing of the installed links.
Theme b- Radiation hardness and reliability of optoelectronic components.
Establish common procedures and common ways to represent the irradiation data, share facilities and coordinate irradiation runs, avoid redundant tests and share results.
Theme c- Common optical link reference test bench.
Define a reference test system for multi-gigabit/s optical links. Define test procedures and evaluation criteria. Specify the interface to the links to be tested. Develop hard, software and FPGA-IP blocks. Purchase test equipment and build reference test bench. Test proposed SLHC links on common reference bench and evaluate with common criteria.
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06

38. ATLAS Tracker Upgrade Liverpool December '06
Outlook
Much more work to do on radiation hardness:
Understand 850 nm VCSEL performance better
Compare damage factors in p/p/n tests.
Start testing 1310 nm VCSELs.
Continue fibre testing to SLHC doses
Test Si and InGaAsP p-i-n diodes to SLHC fluences
Packaging
Custom versus modified COTs
System issues
Need decision on low speed vs high speed links
If we adopt high speed links many detailed questions:
How many modules/link?
Do we want intermediate electrical multiplexing?
How do we introduce some level of redundancy?
Tony Weidberg
ATLAS Tracker Upgrade Liverpool December '06