München 2009 – scientific programme

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T: Fachverband Teilchenphysik

T 72: DAQ und Trigger 3 / Elektronik

T 72.5: Talk

Friday, March 13, 2009, 15:00–15:15, M110

Timing Performance of the ATLAS Pixel Detector — •Iskander Ibragimov — Universität Siegen, Siegen, Deutschland

The ATLAS pixel detector is the innermost tracking detector of the ATLAS experiment at the LHC at CERN. It consists of 1744 identical modules, each made of a silicon sensor read out by 16 front end chips.

At the full LHC luminosity of 10³⁴ cm⁻²s⁻¹ proton bunches will collide roughly every 25 ns. Each hit originating from a collision event has to be assigned to the correct bunch crossing for reconstruction. This requires global and local adjustments of the pixel detector readout. For the global adjustment w.r.t. other ATLAS sub-detectors the proper timing of the ATLAS synchronisation signals together with the optimised global trigger latency are necessary. The local adjustment implies compensation of differences in trigger propagation delays between modules induced by variations in the cable lengths. Another important aspect of the detector timing is the timewalk effect in the front end electronics, which causes losses of low amplitude signals in the next bunch crossing. To minimise the effect, an optimal sampling of collision hits with the clock has to be assured. Using special timing calibration scans the timewalk effect can be measured prior to collisions and its impact on the detector efficiency can be estimated.

In the talk an introduction into the pixel detector readout will be given and the mechanisms for the timing adjustments will be illustrated. Based on recent results from the pixel detector commissioning the current status of the detector timing will be presented.