- Email: [email protected]
EndCap module production of the ATLAS Semiconductor Tracker
ARTICLE IN PRESS
Nuclear Instruments and Methods in Physics Research A 560 (2006) 75–78 www.elsevier.com/locate/nima
EndCap module production of the ATLAS Semiconductor Tracker Shulamit Moed DPNC, University of Geneva, 24, Quai Ernest-Ansermet, 1211 Geneve 4, Switzerland On behalf of the ATLAS Silicon Tracker collaboration Available online 28 December 2005
Abstract ATLAS is one of the four experiments at the Large Hadron Collider at CERN. The ATLAS Semiconductor Tracker (SCT) forms a central part of the tracking system of the inner detector of the ATLAS experiment. It consists of 4 cylindrical barrel layers and 18 end-cap disks of 4088 modules in total made of single-sided p-on-n silicon microstrip detectors with about 6 million read-out channels. Most of the modules consist of 4 single-sided silicon sensors glued back to back with a 40 mrad stereo angle on a support structure, and read-out by custom made ASICs based on radiation hard DMILL technology. The mass production of about 2000 SCT end-cap modules began in mid-2003 at various production sites around the world. r 2005 Elsevier B.V. All rights reserved. PACS: 07.77.Ka; 29.40.Wk Keywords: ATLAS; SCT; Silicon; Microstrip; Detector; EndCap
1. Introduction ATLAS [1] is a general purpose detector designed to exploit the full discovery potential of the Large Hadron Collider (LHC), a 14 TeV proton–proton collider which is under construction at CERN. The ATLAS inner detector [2] (Fig. 1) combines high-resolution detectors in the inner radii with continuous tracking elements at the outer radii, all contained in a central superconducting solenoid that provides an axial magnetic field of 2 T. The momentum and vertex resolution requirements from physics call for highprecision spatial measurements to be made with finegranularity detectors, given the enormous track density expected at the LHC. The Inner Detector therefore consists of three parts: the pixel vertex detector, the SemiConductor Tracker (SCT) and the Transition Radiation Tracker (TRT). 2. Semi-Conductor tracker and module design The SCT [3] will be located between the innermost pixel and the outer TRT at radii between 25 and 50 cm. It E-mail address: [email protected]. 0168-9002/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2005.11.237
consists of a central barrel section (4 barrel layers) and two end-caps (9 end-cap disks on each) allowing for charged particle tracking up to a pseudo-rapidity of 2.5. The total number of silicon micro-strip detector modules that will compose the SCT is 4088 with 1576 readout channels per module and a total of 6.3 million read-out channels. The radiation environment requires the detectors and the electronics to be radiation hard up to a total fluence equivalent to 2 1014 1 MeV neutrons=cm2 for the anticipated 10 years of operation. In order to limit reverse annealing of the silicon detectors, the SCT will operate at an ambient temperature of 7 C. An efficient and accurate track and vertex reconstruction requires an SCT detector efficiency of at least 95%, with a resolution of 16 mm in R f and 500 mm in z-direction. Each SCT EndCap contains 9 disks which are carbonfibre structures of about 1:2 m in diameter. A disk is covered with up to 132 modules arranged in 3 rings: an ‘outer’ ring of 52 modules, and an ‘inner’ and ‘middle’ ring of 40 modules each. This results in a total of 1976 detector modules in the SCT EndCaps. Modules within a ring, as well as different rings overlap in order to minimize gaps in the acceptance. The sensors [4] for the SCT EndCap module are wedge-shaped p-on-n detectors, 285 mm thick
ARTICLE IN PRESS 76
S. Moed / Nuclear Instruments and Methods in Physics Research A 560 (2006) 75–78
Fig. 1. The layout of the ATLAS inner detector.
Fig. 2. Typical noise occupancy plot of one side of the outer EndCap Module (6 chips) as a function of threshold for the whole side.
IVs during module assembly 400
Current[nAmps]
with 768 read-out strips. The strips are about 6 cm long and AC-coupled to the read-out electronics mounted on a hybrid. There are five different sensor designs depending on their radial position and the strip pitch ranging between 55 and 90 mm. The pitch size is 80 mm for barrel modules which also have 768 read-out strips. The sensors are read out by 12 custom designed ASICs (ATLAS Binary Chip DMILL ‘ABCD’ [5]) with 128 channels per ASIC mounted on the hybrid, where each channel provides preamplification, shaping with a time constant of 25 ns, comparators with thresholds which are trimmable for each channel, a digital pipeline which is 132 cells deep to allow for data storage while the first level trigger decision is made, data compression and readout buffers. In this way signals from the sensor are converted to binary hit information in the front-end and the data are transmitted by binary optical links. The barrel, middle and outer forward modules consist of four single sided silicon micro-strip sensors, where two of them are daisy chained to give 12 cm long strips. The silicon sensor pairs are glued back-to-back on a support structure (spine) with a 40 mrad stereo angle providing two-dimensional position information. The spine, the module mechanical support structure, is made of thermal pyrolitic graphite (TPG) with a high in-plane thermal conductivity of 1700 W=mK in order to carry the heat from the detectors to the cooling points at the side or end of the modules. The inner and short-middle EndCap module design follows the same concept, except for the fact that only two sensors are used, one on each side resulting in modules of about 6 cm strip length. The most important parameters for the binary performance of the module are the efficiency and the noise occupancy at the nominal operating threshold. The module specifications require 499% efficiency and o5 104 for the noise occupancy (Fig. 2). Test-beam studies have shown that these benchmark numbers can be reached for a corrected threshold of 1 fC for non-irradiated modules. For irradiated modules the noise occupancy can be reached using a threshold of 1:2 fC with a slight efficiency loss [6,7].
300 before assembly 200 after spine gluing after hybrid gluing 100
0
after bonding
0
200 Voltage[V]
400
Fig. 3. IV measurements of modules during different assembly stages.
3. Module production Production of the 4088 modules takes place at several sites worldwide—4 barrel module assembly sites in Japan, Scandinavia, UK and the USA; 7 forward assembly sites in Australia, Germany, Netherlands, Spain, Switzerland and the UK. Each production site needs to pass strict qualification procedures verifying its ability to start module production. At the University of Geneva and CERN site a total number of about 624 outer end-cap modules will be produced and tested. After assembly and metrology survey at the University of Geneva the modules arrive to CERN for quality assurance. The tests are performed in a laboratory with clean room facilities and infrastructure. 4. Production at the Geneva University At the University of Geneva only modules for the outer rings are assembled. The sensors are produced by Hamamatsu and have polysilicon bias resistors while the CiS sensors used for production in some of the other assembly institutes have implanted bias resistors.
ARTICLE IN PRESS S. Moed / Nuclear Instruments and Methods in Physics Research A 560 (2006) 75–78
gives the mounting precision in the y direction when mounting the module, the fan-ins—pitch adaptors, etc.
Components that are to be assembled to a module have to be inspected and tested. Before assembly the following tests are made:
Visual inspection and electrical tests of the hybrid performance. The hybrids arrive to Geneva from the hybrid quality assurance sites where they were qualified. However a sequence of confirmation tests after the transport to Geneva is performed to verify the electrical functionality. IV measurements of the individual silicon sensors. Inspection of mechanical pieces—the spine, the padlocator which is a precision locator for the alignment of the module when mounted, the far-end washer which
77
During the assembly of a module an IV measurement of each of the 4 detectors mounted to the module is made after each assembly phase (Fig. 3)—after gluing the sensors to the spine and after gluing the hybrid to the module; an IV measurement of the whole module is done once the module is fully wire-bonded. When the assembly is completed the module is put through a thermal cycling in order to verify that operating over a range of different temperatures does not compromise the mechanical layout of the module and the thermal specified limits. The electrically unconnected module is put
Z Metrology Statistics, Geneva Entries 385 385 Average Z(mm) - modules front side Mean 0.8721 Mean 0.8721 RMS RMS 0.02451 0.02451 Underflow 00 Underflow Overflow 11 Overflow
Average Z(mm) - modules back side 100
385
Mean
-0.3796
RMS
0.01916
Underflow
0
Overflow
0
number of modules
number of modules
100
50
0
50
0 0.7 0.8 0.9 1 position relative to module reference zero [mm] RMS Z - modules front side
RMS Z - modules back side
0
0.02
0.04 rms
385
0.02256
Mean Mean
0.01846
RMS RMS
0.007938
RMS RMS
0.006025
Underflow Underflow
00
Underflow Underflow
0
Overflow Overflow
44
Overflow Overflow
0
20
0
385 385
Mean Mean
40
number of modules
number of modules
40
Entries
-0.5 -0.4 -0.3 -0.2 position relative to module reference zero [mm]
0.06
20
0
0
0.02
0.04
0.06
rms
Fig. 4. Summary of Z profile distributions for modules completed and tested so far at the University of Geneva, using the Geneva statistics package. Vertical lines represent the specified limits—production well within specifications.
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S. Moed / Nuclear Instruments and Methods in Physics Research A 560 (2006) 75–78
in a climate chamber, supported on a jig without stress in the xy-plane but forced to be flat in the z-direction using vacuum. Over a 17 h period the temperatures of the modules are cycled 10 times between 30 and þ35 C. A controlled flow of nitrogen is supplied to the inside of the climate chamber in order to control the dew point. Once the thermal cycling is completed a final survey of the module profile (metrology) is made. Then various electrical tests of the module are executed during which an internal calibration of the module is made by injecting a charge of known amplitude in the preamplifier of each channel. In this way, channel to channel threshold variations are adjusted. The tests ensure that the electrical specifications of the module performance are met. For example, using threshold scans it is checked that with a nominal threshold setting to 1 fC, the noise occupancy does not exceed the limit of 5 104 or that the equivalent noise charge (ENC) per chip is not exceeding 1600 electrons. Moreover, the number of bad channels (unbonded channels, or channels that give low gain, high noise, etc.) has to be less than 1%. Completed modules that pass all tests are shipped to CERN for quality assurance. The quality assurance procedure includes a ‘long term’ test that lasts 24 h during which the modules are put in a climate chamber and a sequence of confirmation tests is executed every 2 h in order to check the stability of the modules. By November 2004, 310 outer modules were produced at the University of Geneva and shipped to CERN for quality assurance. After assembly the modules are classified as:
Good: if all specifications are met. Pass: if the metrology measurements are within 15% tolerance and a smooth IV-curve, that does not exceed the current limit of 80 mA is obtained up to a minimum breakdown voltage of 350 V (150 V for CiS sensors). Hold: if electrical specifications are not met but at least a smooth IV curve is obtained up to 150 V (Hamamatsu) and all chips are responding. The module is also assigned to this category if the metrology measurement identifies outliers with respect to the nominal envelope. Fail: if the module does not match any of the above categories and is not re-workable.
The assembly efficiency in the University of Geneva (‘good’ modules) up to now is 95%. A statistics package which plots distributions of different parameters characterizing the module performance and mechanical structure has been developed in Geneva and is used by the SCT institutes in order to monitor the quality and rate of the production. Fig. 4 shows four example distributions for the Z profile measurements of the modules made using the statistics package.
Fig. 5. EndCap modules mounted on a integration area at CERN.
1 4
of a disk at the ATLAS
5. Summary The ATLAS SCT represents a major part of the ATLAS inner detector. Production and tests so far have demonstrated that the requirements for mechanical precisions of the SCT can be met and that the electrical performance of produced modules satisfies the design specifications. A SystemTest setup at CERN (Fig. 5) where a 14 of an SCT disk is inside a shielding box has helped developing good grounding and shielding schemes and verified module performance when mounted on a disk. The production of barrel modules is complete and the EndCap module production is well underway. However, electrical tests of the completed barrels and disks and the integration into the ATLAS inner detector are still a major effort. References [1] ATLAS Technical Proposal, CERN/LHCC/94-43, hhttp://atlasinfo.cern. ch/ATLASi, 1993. [2] ATLAS Inner Detector Technical Design Report, CERN/LHCC9716, CERN/LHCC97-17, 1997. [3] The ATLAS Semiconductor Tracker (SCT), hhttp://atlas.web.cern.ch/ Atlas/GROUPS/INNERDETECTOR/SCTi. [4] L. Andricek, et al., Nucl. Instr. and Meth. A 439 (2000) 427; D. Robinson, et al., Nucl. Instr. and Meth. A 485 (2002) 84. [5] ABCD Chip Specification, Version 2.0, December 12, 1998; W. Dabrowski, J. Kaplon, R. Szczygiel, Nucl. Instr. and Meth. A 421 (1999) 303. [6] F. Campabal, et al., Beam tests of ATLAS SCT silicon strip detector modules, Nucl. Instr. and Meth. A 538 (1–3) (2005) 384–407. [7] Electrical test results from ATLAS-SCT end-cap modules, M. Mangin-Brinet, et al., ATL-INDET-2003-004.
Nuclear Instruments and Methods in Physics Research A 560 (2006) 75–78 www.elsevier.com/locate/nima
EndCap module production of the ATLAS Semiconductor Tracker Shulamit Moed DPNC, University of Geneva, 24, Quai Ernest-Ansermet, 1211 Geneve 4, Switzerland On behalf of the ATLAS Silicon Tracker collaboration Available online 28 December 2005
Abstract ATLAS is one of the four experiments at the Large Hadron Collider at CERN. The ATLAS Semiconductor Tracker (SCT) forms a central part of the tracking system of the inner detector of the ATLAS experiment. It consists of 4 cylindrical barrel layers and 18 end-cap disks of 4088 modules in total made of single-sided p-on-n silicon microstrip detectors with about 6 million read-out channels. Most of the modules consist of 4 single-sided silicon sensors glued back to back with a 40 mrad stereo angle on a support structure, and read-out by custom made ASICs based on radiation hard DMILL technology. The mass production of about 2000 SCT end-cap modules began in mid-2003 at various production sites around the world. r 2005 Elsevier B.V. All rights reserved. PACS: 07.77.Ka; 29.40.Wk Keywords: ATLAS; SCT; Silicon; Microstrip; Detector; EndCap
1. Introduction ATLAS [1] is a general purpose detector designed to exploit the full discovery potential of the Large Hadron Collider (LHC), a 14 TeV proton–proton collider which is under construction at CERN. The ATLAS inner detector [2] (Fig. 1) combines high-resolution detectors in the inner radii with continuous tracking elements at the outer radii, all contained in a central superconducting solenoid that provides an axial magnetic field of 2 T. The momentum and vertex resolution requirements from physics call for highprecision spatial measurements to be made with finegranularity detectors, given the enormous track density expected at the LHC. The Inner Detector therefore consists of three parts: the pixel vertex detector, the SemiConductor Tracker (SCT) and the Transition Radiation Tracker (TRT). 2. Semi-Conductor tracker and module design The SCT [3] will be located between the innermost pixel and the outer TRT at radii between 25 and 50 cm. It E-mail address: [email protected]. 0168-9002/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2005.11.237
consists of a central barrel section (4 barrel layers) and two end-caps (9 end-cap disks on each) allowing for charged particle tracking up to a pseudo-rapidity of 2.5. The total number of silicon micro-strip detector modules that will compose the SCT is 4088 with 1576 readout channels per module and a total of 6.3 million read-out channels. The radiation environment requires the detectors and the electronics to be radiation hard up to a total fluence equivalent to 2 1014 1 MeV neutrons=cm2 for the anticipated 10 years of operation. In order to limit reverse annealing of the silicon detectors, the SCT will operate at an ambient temperature of 7 C. An efficient and accurate track and vertex reconstruction requires an SCT detector efficiency of at least 95%, with a resolution of 16 mm in R f and 500 mm in z-direction. Each SCT EndCap contains 9 disks which are carbonfibre structures of about 1:2 m in diameter. A disk is covered with up to 132 modules arranged in 3 rings: an ‘outer’ ring of 52 modules, and an ‘inner’ and ‘middle’ ring of 40 modules each. This results in a total of 1976 detector modules in the SCT EndCaps. Modules within a ring, as well as different rings overlap in order to minimize gaps in the acceptance. The sensors [4] for the SCT EndCap module are wedge-shaped p-on-n detectors, 285 mm thick
ARTICLE IN PRESS 76
S. Moed / Nuclear Instruments and Methods in Physics Research A 560 (2006) 75–78
Fig. 1. The layout of the ATLAS inner detector.
Fig. 2. Typical noise occupancy plot of one side of the outer EndCap Module (6 chips) as a function of threshold for the whole side.
IVs during module assembly 400
Current[nAmps]
with 768 read-out strips. The strips are about 6 cm long and AC-coupled to the read-out electronics mounted on a hybrid. There are five different sensor designs depending on their radial position and the strip pitch ranging between 55 and 90 mm. The pitch size is 80 mm for barrel modules which also have 768 read-out strips. The sensors are read out by 12 custom designed ASICs (ATLAS Binary Chip DMILL ‘ABCD’ [5]) with 128 channels per ASIC mounted on the hybrid, where each channel provides preamplification, shaping with a time constant of 25 ns, comparators with thresholds which are trimmable for each channel, a digital pipeline which is 132 cells deep to allow for data storage while the first level trigger decision is made, data compression and readout buffers. In this way signals from the sensor are converted to binary hit information in the front-end and the data are transmitted by binary optical links. The barrel, middle and outer forward modules consist of four single sided silicon micro-strip sensors, where two of them are daisy chained to give 12 cm long strips. The silicon sensor pairs are glued back-to-back on a support structure (spine) with a 40 mrad stereo angle providing two-dimensional position information. The spine, the module mechanical support structure, is made of thermal pyrolitic graphite (TPG) with a high in-plane thermal conductivity of 1700 W=mK in order to carry the heat from the detectors to the cooling points at the side or end of the modules. The inner and short-middle EndCap module design follows the same concept, except for the fact that only two sensors are used, one on each side resulting in modules of about 6 cm strip length. The most important parameters for the binary performance of the module are the efficiency and the noise occupancy at the nominal operating threshold. The module specifications require 499% efficiency and o5 104 for the noise occupancy (Fig. 2). Test-beam studies have shown that these benchmark numbers can be reached for a corrected threshold of 1 fC for non-irradiated modules. For irradiated modules the noise occupancy can be reached using a threshold of 1:2 fC with a slight efficiency loss [6,7].
300 before assembly 200 after spine gluing after hybrid gluing 100
0
after bonding
0
200 Voltage[V]
400
Fig. 3. IV measurements of modules during different assembly stages.
3. Module production Production of the 4088 modules takes place at several sites worldwide—4 barrel module assembly sites in Japan, Scandinavia, UK and the USA; 7 forward assembly sites in Australia, Germany, Netherlands, Spain, Switzerland and the UK. Each production site needs to pass strict qualification procedures verifying its ability to start module production. At the University of Geneva and CERN site a total number of about 624 outer end-cap modules will be produced and tested. After assembly and metrology survey at the University of Geneva the modules arrive to CERN for quality assurance. The tests are performed in a laboratory with clean room facilities and infrastructure. 4. Production at the Geneva University At the University of Geneva only modules for the outer rings are assembled. The sensors are produced by Hamamatsu and have polysilicon bias resistors while the CiS sensors used for production in some of the other assembly institutes have implanted bias resistors.
ARTICLE IN PRESS S. Moed / Nuclear Instruments and Methods in Physics Research A 560 (2006) 75–78
gives the mounting precision in the y direction when mounting the module, the fan-ins—pitch adaptors, etc.
Components that are to be assembled to a module have to be inspected and tested. Before assembly the following tests are made:
Visual inspection and electrical tests of the hybrid performance. The hybrids arrive to Geneva from the hybrid quality assurance sites where they were qualified. However a sequence of confirmation tests after the transport to Geneva is performed to verify the electrical functionality. IV measurements of the individual silicon sensors. Inspection of mechanical pieces—the spine, the padlocator which is a precision locator for the alignment of the module when mounted, the far-end washer which
77
During the assembly of a module an IV measurement of each of the 4 detectors mounted to the module is made after each assembly phase (Fig. 3)—after gluing the sensors to the spine and after gluing the hybrid to the module; an IV measurement of the whole module is done once the module is fully wire-bonded. When the assembly is completed the module is put through a thermal cycling in order to verify that operating over a range of different temperatures does not compromise the mechanical layout of the module and the thermal specified limits. The electrically unconnected module is put
Z Metrology Statistics, Geneva Entries 385 385 Average Z(mm) - modules front side Mean 0.8721 Mean 0.8721 RMS RMS 0.02451 0.02451 Underflow 00 Underflow Overflow 11 Overflow
Average Z(mm) - modules back side 100
385
Mean
-0.3796
RMS
0.01916
Underflow
0
Overflow
0
number of modules
number of modules
100
50
0
50
0 0.7 0.8 0.9 1 position relative to module reference zero [mm] RMS Z - modules front side
RMS Z - modules back side
0
0.02
0.04 rms
385
0.02256
Mean Mean
0.01846
RMS RMS
0.007938
RMS RMS
0.006025
Underflow Underflow
00
Underflow Underflow
0
Overflow Overflow
44
Overflow Overflow
0
20
0
385 385
Mean Mean
40
number of modules
number of modules
40
Entries
-0.5 -0.4 -0.3 -0.2 position relative to module reference zero [mm]
0.06
20
0
0
0.02
0.04
0.06
rms
Fig. 4. Summary of Z profile distributions for modules completed and tested so far at the University of Geneva, using the Geneva statistics package. Vertical lines represent the specified limits—production well within specifications.
ARTICLE IN PRESS 78
S. Moed / Nuclear Instruments and Methods in Physics Research A 560 (2006) 75–78
in a climate chamber, supported on a jig without stress in the xy-plane but forced to be flat in the z-direction using vacuum. Over a 17 h period the temperatures of the modules are cycled 10 times between 30 and þ35 C. A controlled flow of nitrogen is supplied to the inside of the climate chamber in order to control the dew point. Once the thermal cycling is completed a final survey of the module profile (metrology) is made. Then various electrical tests of the module are executed during which an internal calibration of the module is made by injecting a charge of known amplitude in the preamplifier of each channel. In this way, channel to channel threshold variations are adjusted. The tests ensure that the electrical specifications of the module performance are met. For example, using threshold scans it is checked that with a nominal threshold setting to 1 fC, the noise occupancy does not exceed the limit of 5 104 or that the equivalent noise charge (ENC) per chip is not exceeding 1600 electrons. Moreover, the number of bad channels (unbonded channels, or channels that give low gain, high noise, etc.) has to be less than 1%. Completed modules that pass all tests are shipped to CERN for quality assurance. The quality assurance procedure includes a ‘long term’ test that lasts 24 h during which the modules are put in a climate chamber and a sequence of confirmation tests is executed every 2 h in order to check the stability of the modules. By November 2004, 310 outer modules were produced at the University of Geneva and shipped to CERN for quality assurance. After assembly the modules are classified as:
Good: if all specifications are met. Pass: if the metrology measurements are within 15% tolerance and a smooth IV-curve, that does not exceed the current limit of 80 mA is obtained up to a minimum breakdown voltage of 350 V (150 V for CiS sensors). Hold: if electrical specifications are not met but at least a smooth IV curve is obtained up to 150 V (Hamamatsu) and all chips are responding. The module is also assigned to this category if the metrology measurement identifies outliers with respect to the nominal envelope. Fail: if the module does not match any of the above categories and is not re-workable.
The assembly efficiency in the University of Geneva (‘good’ modules) up to now is 95%. A statistics package which plots distributions of different parameters characterizing the module performance and mechanical structure has been developed in Geneva and is used by the SCT institutes in order to monitor the quality and rate of the production. Fig. 4 shows four example distributions for the Z profile measurements of the modules made using the statistics package.
Fig. 5. EndCap modules mounted on a integration area at CERN.
1 4
of a disk at the ATLAS
5. Summary The ATLAS SCT represents a major part of the ATLAS inner detector. Production and tests so far have demonstrated that the requirements for mechanical precisions of the SCT can be met and that the electrical performance of produced modules satisfies the design specifications. A SystemTest setup at CERN (Fig. 5) where a 14 of an SCT disk is inside a shielding box has helped developing good grounding and shielding schemes and verified module performance when mounted on a disk. The production of barrel modules is complete and the EndCap module production is well underway. However, electrical tests of the completed barrels and disks and the integration into the ATLAS inner detector are still a major effort. References [1] ATLAS Technical Proposal, CERN/LHCC/94-43, hhttp://atlasinfo.cern. ch/ATLASi, 1993. [2] ATLAS Inner Detector Technical Design Report, CERN/LHCC9716, CERN/LHCC97-17, 1997. [3] The ATLAS Semiconductor Tracker (SCT), hhttp://atlas.web.cern.ch/ Atlas/GROUPS/INNERDETECTOR/SCTi. [4] L. Andricek, et al., Nucl. Instr. and Meth. A 439 (2000) 427; D. Robinson, et al., Nucl. Instr. and Meth. A 485 (2002) 84. [5] ABCD Chip Specification, Version 2.0, December 12, 1998; W. Dabrowski, J. Kaplon, R. Szczygiel, Nucl. Instr. and Meth. A 421 (1999) 303. [6] F. Campabal, et al., Beam tests of ATLAS SCT silicon strip detector modules, Nucl. Instr. and Meth. A 538 (1–3) (2005) 384–407. [7] Electrical test results from ATLAS-SCT end-cap modules, M. Mangin-Brinet, et al., ATL-INDET-2003-004.