Abstract
We report on the operation and performance of the ATLAS Semi-Conductor Tracker(SCT), which has been functioning for 3 years in a high luminosity,high radiation environment. The SCT is constructed of 4088 silicondetector modules, for a total of 6.3 million strips. Each moduleoperates as a stand-alone unit, mechanically, electrically, opticallyand thermally. The modules are mounted into two types of structures:one barrel, made of 4 cylinders, and two end-cap systems made of 9disks. The SCT silicon micro-strip sensors are processed in the planarp-in-n technology. The signals are processed in the front-end ABCD3TAASICs, which use a binary readout architecture. Data is transferredto the off-detector readout electronics via optical fibres. We find99.3% of the SCT modules are operational, the noise occupancy andhit efficiency exceed the design specifications; the alignment is veryclose to the ideal to allow on-line track reconstruction and invariantmass determination. We will report on the operation and performance ofthe detector including an overview of the issues encountered. Weobserve a significant increase in leakage currents from bulk damagedue to non-ionizing radiation and make comparisons with thepredictions. We will also cover the time evolution of the keyparameters of the strip tracker, including the evolution of noise andgain, the measurement of the Lorentz angle and the tracking efficiencyin the harsh LHC environment. Valuable lessons for future siliconstrip detector projects will be presented.
Highlights
The Semi-Conductor Tracker (SCT) consists of 4088 detector modules, which are the smallest stand-alone unit of readout
A global fit is run to minimise track residuals by introducing changes in geometry down to the module level. 3.2 Leakage current The leakage current through the silicon wafers is measured by the high-voltage cards which provide the detector bias from the counting room
When the holes produced by a charged particle in the silicon detector drift towards the strip, they are under the influence of both the electric field produced by the bias voltage and the magnetic field generated by the solenoid around the inner detector
Summary
The SCT consists of 4088 detector modules, which are the smallest stand-alone unit of readout These are arranged into 4 barrel cylinders and 2 end-caps each with 9 disks. All of the inner modules and the modules in the middle ring of disk 8 have a single detector on each side, and so have shorter strips. In the counting room the back of crate cards (BOCs) handle the optical encoding and decoding to electrical signals which are sent to/from the detector readout drivers (RODs). These RODs aggregate the data from up to 48 modules and send it to ATLAS over high-speed serial optical fibres
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