Abstract
37 pages, 43 figures.-- PACS nrs.: 29.40.Gx; 29.40.Wk.-- ISI Article Identifier: 000247146800010.-- et al.
The challenges for the tracking detector systems at the LHC are unprecedented in terms of the number of channels, the required read-out speed and the expected radiation levels. The ATLAS Semiconductor Tracker (SCT) end-caps have a total of about 3 million electronics channels each reading out every 25 ns into its own on-chip 3.3 μs buffer. The highest anticipated dose after 10 years operation is 1.4x10(14) cm(-2) in units of 1 MeV neutron equivalent (assuming the damage factors scale with the non-ionising energy loss). The forward tracker has 1976 double-sided modules, mostly of area similar to 70 cm(2), each having 2 x 768 strips read out by six ASICs per side. The requirement to achieve an average perpendicular radiation length of 1.5% X-0, while coping with up to 7 W dissipation per module (after irradiation), leads to stringent constraints on the thermal design. The additional requirement of 1500e(-) equivalent noise charge (ENC) rising to only 1800e(-) ENC after irradiation, provides stringent design constraints on both the high-density Cu/Polyimide flex read-out circuit and the ABCD3TA read-out ASICs. Finally, the accuracy of module assembly must not compromise the 16 μm (rΦ) resolution perpendicular to the strip directions or 580 μm radial resolution coming from the 40 mrad front-back stereo angle. A total of 2210 modules were built to the tight tolerances and specifications required for the SCT. This was 234 more than the 1976 required and represents a yield of 93%. The component flow was at times tight, but the module production rate of 40-50 per week was maintained despite this. The distributed production was not found to be a major logistical problem and it allowed additional flexibility to take advantage of where the effort was available, including any spare capacity, for building the end-cap modules. The collaboration that produced the ATLAS SCT end-cap modules kept in close contact at all times so that the effects of shortages or stoppages at different sites could be rapidly resolved.
We acknowledge the support of the funding
authorities of the collaborating institutes including the Spanish National Programme for Particle Physics; the Research Council of Norway; the Particle Physics and Astronomy Research Council of the United Kingdom; the
Polish Ministry of Education and Science; the German Ministry of Science; the Swiss National Science Foundation; the State Secretariat for Education and Research and the Canton of Geneva; the Slovenian Research Agency and the Ministry of Higher Education, Science and Technology of the Republic of Slovenia; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Japan Society for the Promotion of Science; the Office of High Energy Physics of the United States Department of Energy; the United States National Science Foundation; the Australian Department of Education, Science and Training; Dutch Foundation for Fundamental Research on Matter (FOM); the Ministry of Education, Youth and
Sports of the Czech Republic; the National Science Council, Taiwan; the Swedish Research Council. The Research was supported in part by the EU under RTN Contract HPRN-CT-2002-00292 Probe for New Physics within the Sixth European Community Framework Programme.
Peer reviewed