Overview
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The ATLAS Semi-Conductor Tracker (SCT) Collaboration is currently in the production phase of fabricating
and testing silicon strips modules for the ATLAS detector at the Large Hadron Collider being built
at the CERN laboratory in Geneva, Switzerland.
The SCT system is designed to provide eight precision measurements per track in the intermediate
radial range, contributing to the measurement of momentum, impact parameter and vertex position.
In the barrel SCT eight layers of silicon microstrip detectors provide precision point in the
r-f and z coordinates, using small angle stereo to obtain the
z-measurement. The SCT covers a pseudorapidity-range < 2.5.
The SCT will consist of 4 cylindrical layers in the central region of the
Inner Detector, at 300, 373, 447, and 520 mm radii from the beam line, and 9 end-cap disks on each side
of the barrel detector. The Barrel and End-Cap are populated with 4,088 silicon strips modules with
a total area of silicon of 61 m2.
The ATLAS SCT module is built with 2 pairs of identical, single-sided silicon micro-strips sensors
(768 AC-coupled, p-strips on n-type silicon, 80 mm strips pitch) glued back-to-back, with
a 40 mrad stereo angle on a mechanical core (baseboard) made of thermal pyrolitic graphite (TPG) to transfer
the heat generated by the readout electronics and sensors to the cooling pipe.
Each pair of strips sensors is wire bonded to form double-long strips of 126 mm length.
A hybrid flexible circuit made of copper/polyimide laminate is wrapped around the two sides of the sensors
at the center of the module, bridged over the sensors.
The Front-End readout of the SCT is handled by ASICS realized in the radiation hard DMILL technology,
named ABCD3T [5], featuring a 128-channel analogue front-end consisting of amplifiers and comparators,
and a digital readout circuit, and operates at the LHC bunch crossing frequency of 40 MHz.
The full SCT requires ~50,000 ICs for a total of 6.2 million readout channels.
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