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System description

Specifications

Radiation envionment
Optopackages
ASICs (see under electronics below)
Fibres (see under Optical Fibre and connectors below).
Off-detector arrays of PINs and VCSELs

Radiation hardness tests

Radiation hardness of ASICs

Components

optical fiber and connectors

opto-electronic components

PIN
LED (historical information, LEDs are no longer used in the SCT links)
VCSEL - information on the VCSEL tests performed at Bern is available. More information on VCSELs is available .
On-detector packages containing VCSELs and PINs.
Off-detector arrays of VCSELs and PINs from Truelight
( Obsolete off-detector arrays of VCSELs and PINs )

electronics

DORIC4A specs pdf file
VCSEL Driver Chip (VDC) specs pdf file
BPM-12 specs pdf file and pinou t pdf file
PIN Diode anplifier/discriminator (DRX) specs pdf file
Power budget for on-detector opto-electronics
Off-detector electronics BOC
Test plan for DORIC4A and VDC pdf file
Wafer maps from the production runs for the ASICs

Cables

low mass Al power tapes
Cu kapton cable. System test '98 version of dog-leg cable and opto-hybrid .
Proposed opto-flex cable. Preliminary versions for module-1s and module-0s: PCB layout schematic and DXF files available here .
A pulsed thermode has been used for soldering Al and Cu low mass tapes. The results of peel strngths for different settings are availabele as a ps file or a pdf file

Radiation Length Estimate for opto-links

barrel opto-harness (material at 90 degrees averaged over SCT module area) EXCEL: file or ps file
forward fibre-harnes

Interfaces

Barrel: 6 opto-flex cables will be connected to 6 low mass tapes to form a harness. a drawing of such a harness mounted on the barrel is available here . A drawing of a harness in a test jig is available here .
Forward: the opto-packages will be mounted on PCBs with connectors to form a pluggable package. This package then plugs into the forward hybrid. The DORIC and VDC chips are mounted on the hybrid. A schematic drawing of the pluggable opto-package is available here . A drawing of the current prototype for the PCB is available as a postscript file . A drawing of the plastic cover for the forward plug-in opto PCB is available here ( postscript file ).
New Integrated Forward opto-packages. A new design of opto-packages has been produced in which the opto-packages are built up directly onto the forward plug-in PCB. This eliminates the extra wire bonding step and the need for a protective cover exposed wire bonds. A photo of one of these integrated opto plug-ins is available here and a photo of intergrated opto plug-in on a burn-in PCB is available here .

Barrel Opto-Harness Tests

one opto-harness was assmebled with Taiwan opto-packages. Many problems with the assembly procedure were found and impriovements are in place for the assembly of a second harness with the Taiwan opto-packages in October.
A second opto-harness with Taiwan opto-packages was assembled in October. All data and TTC channels work ok. Photos of the harness on the test jig are available ( photo1 , photo2 ). Photos of the dog-leg showing the opto-package and ASICs are available ( photo1 , photo2 , photo3 ). The test result data are available ( ps file ) .
photos of a left-handed harness are available here .
A first opto-harness has been assembled with the Marconi opto-packages. A summary of the status and test data is available as a PowerPoint file.
A third left-handed harness has beem assembled with the Taiwan opto-packages. Photos illustrating the assembly sequence for this harness are available here . A summary of the test data is available as a Power Point file.
A module-1 right-handed harness has beem assembled with the Taiwan opto-packages. A summary of the test data is available as a Power Point file .
Photos showing mounting of harness on sector at system test.
results from the first module 0 style barrel harnes ( EXCEL file ). This harness was designed to be compatible with the new round cooling pipe. There are still some small mechanical changes required to fit on the barre which will be implemented on the next harness. There are also more changes required for the thermal management which will be implemented in future harnesses.
Results from the tests of the pre-series barrel harness are available here.

Forward Fibre Harness Tests

A first forward fibre harness has been assembled with the Taiwan opto-packages mounted on the plug-in PCB with plastic lids over the opto-package. The harness consists of 6 plug-in PCBs each containing 2VCSELs (Truelight) and one PIN diode(Teuelight). The 12 data fibres are fusion spliced to a 12 way ribbon and the 6 TTC fibres are fusion spliced to a 6 way ribbon. There is an MT12(MT8) connector at the end of the data (TTC)ribbon. See the photo of the completed fibre harness and the photo of the opto plug-in tester. A summary of the test data is available and as a Powerpoint file . The second forward fibre harness has been assembled using the Taiwan opto-packages integrated onto the plug-in PCB. This harness is fully functional. Photos illustrating the assembly sequence for this harness are available here and the results of the BER scans are available as a Powerpoint file .
The EXCEL files with the results of the BER scans for all the prototype forward fibre harnesses are available here .
BER measurements were performed with a plug-in opto-package on a K5 hybrid. A short report is available here.

`System Tests`

Barrel Sector Tests at CERN

Four of the module-1 style barrel harnesses have been assembled (see above) and operated successfully at the CERN system test. Extensive results are available from the CERN system test web pages.

Forward Disk Tests at CERN

6 forward fibre harnesses have also been assembled and these are now starting to be be used in the forward SCT system test at CERN.

New B3 Sector Tests at Oxford/RAL

Eight pre-series barrel harnesses are being produced in Taiwan. These harnesses will be mounted on the new B3 sector and used to readout SCT modules. Latest results are available here.

Chip Tests

VDC

first tests of VDC show that it works well. Click here for a scope picture of the optical power from A HFE4080 VCSEL driven by a VDC. The VCSEL drive current was set to 10 mA and the optical power was about 1mW. The rise and fall times were about 1ns. The VDC was packaged in a 40 pin DIL package and the VCSEL was in an ST package so that there is a small amount of ringing on the signal which should not be there for VDC and the VCSEL in a GEC package.

BPM

First tests of BPM4-A show that most features work correctly. Biphase mark encoded data is correctly generated and the delays can be asjusted as expected. There is one significant problem with the output driver pads which means that the VCSEL current is not adjustable and will always be set to maximum (about 35 mA). A scope picture showing input clock and data and output biphase mark encoded data is availabel here.
First tests with the BPM-4B show that the first 3 channels appears to work ok but the 4th chanel gives no output on all chips. Eight out of 10 packaegd chips tested work.The output power can be varried smoothly (unlike BPM-4A). The plot from an optical power scan is available here . The output drive current for all working channels as measured with a test resistor at the output instead of a VCSEL has been measured. See the plots for channel1 , channel2 , , channel3 , and the summary average plot .

BPM-12 Tests

DRX

First tests of the DRX (Digital Receiver Chip) show that it works well. The chip works with input signals down to the specified minimum value of 45 microA. Of the 20 chips delivered, one was damaged in packaging and the remaining 19 show all 4 channels working. The final prototype of the chip will have 12 channels and has been submitted in September. 99 and will be tested in February 2000.

Tests in a Magnetic Field

The MITEL VCSELs in a Marconi package were tested in magnetic fields of up to 6T at the Birmingham solenoid. No deterioration of the VCSEL performance was observed. A short report is available here.

Environmental Tests

The performance of an irradiated Marconi Phase 2 package as a function of temperature has been measured. A short report is available here.
Measurements of an un-irradiated Taiwan opto-package as a function of temperature have been made. The summary plots are available here.

Thermal tests were made of a dogleg with a dummy heater, connected to a cooling block. The results are available as a PowerPoint file.

Production Plans

Assembly and test of opto-harness

Current draft of SOP (Standard Operator Procedure) for barrel harnesses available here .
Current draft of detailed assembly sequence for forward fibre harnesses available here .
See also EDMS notes:

Barrel Harness Assembly QA: ATL-IS-QA-0007
SCT Barrel Opto Harness Acceptance Tests: ATL-IS-ES-0058
SCT Forward Fibre Harness Acceptance Tests: ATL-IS-ES-0060

Production Status

The barrel and EC harness production has completed in Radiamtech, Taiwan.

NIM Papers

The following papers are published or are accepted for publication.

A life time test of neutron irradiated light emitting diodes. Nucl. Instr. Meth. A 373 (1996) 320.
A prototype LED/PIN diode optical data links for the ATLAS semiconductor tracker. Nucl. Instr. Meth. A (1997) 119.
Radiation Hardness and Life Time Studies of LEDs and VCSELs for the Optical Readout of the ATLAS SCT. Nucl. Instr. Meth. A 435 (1999) 375.
Irradiation test of photodiodes for the ATLAS SCT readout. Nucl. Instr. Meth. A 424 (1999) 483.
System Tests of radiation hard optical links for the ATLAS Semiconductor Tracker. Nucl. Instr. Meth. A443 (2000) 430.
Radiation Hardness and Lifetime Studies of the Photodiodes for the Optical Readout of the ATLAS SCT. Nucl. Instr. Meth. A 456 (2000) 292. Preprint available here
Irradiation Studies of Multimode Optical Fibres for use in ATLAS front-end links. Nucl. Instr. Meth. A446 (2000) 426. Preprint available here
Radiation Hardness Studies of the Front-end ASICs for the Optical Links of the ATLAS SemiConductor Tracker. Nucl. Instr. Meth. A457 (2001) 369. Preprint available here .
Single Event Upset Studies with the Optical Links of the ATLAS SemiConductor Tracker. Nucl. Instr. Meth. A481 (2002) 575. Preprint available here .
Radiation Hardness and Lifetime Studies of the VCSEL for the ATLAS SemiConductor Tracker. Nucl. Instr. Meth. A497 (2003) 294. Preprint available here .
The Off-Detector Opto-electronics for the Optical Links of the ATLAS SemiConductor Tracker and Pixel Detector, Nucl Inst. Meth.A530 (2004) 293.
Resonant Bond Wire Vibrations in the ATLAS SemiConductor Tracker, Nucl. Instr. Meth. A538 (2005) 442.

Close Out Review

Conference Proceedings

The following papers were presented to the 4th workshop on LHC electronics, Rome, September 1998.

Other Conferences

Optorad Paris December '98. G. Mahout's transparencies

LEB 2000. Cracow September 2000. Radiation hard optical links for the ATLAS SCT and Pixel detectors. ( word or ps files).

LEB 2001. Stockholm September 2001. Status Report on the SCT Optical Links. Paper word or presentation ppt .

LEB 2002. Colmar September 2002. Status Report on the SCT Optical Links. Paper word doc .

LEB 2005 Heidelberg October 2005. The Production of the SCT Optical Links word doc.

Meetings

The minutes of old meetings are available below. Minutes and agendas for recent meetings are available on the ATLAS agenda system

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For comments, please contact Tony Weidberg
Last update 26 May 1997