Status and performance of the ATLAS Pixel Detector after 3 years of operation

Abstract

The ATLAS Pixel Detector is the innermost detector of the ATLAS experiment at the Large Hadron Collider at CERN. The detector provides hermetic coverage with three cylindrical layers and three disks of Pixel Detectors on each side. It consists of approximately 80 million pixels that are individually read out via chips bump-bonded to 1744 n-in-n silicon substrates. In what follows, results from the successful operation of the Pixel Detector at the LHC and its status after 3 years of operation will be presented, including monitoring, calibration procedures and detector performance. The record breaking instantaneous luminosities of 7.7×1033cm−2s−1 recently reached at the Large Hadron Collider generate a rapidly increasing particle fluence in the ATLAS Pixel Detector. As the radiation dose accumulates, the first effects of radiation damage are now observable in the silicon sensors. A regular monitoring program has been conducted and reveals an increase in the silicon leakage current, which is found to be correlated with the rising radiation dose recorded by independent sensors within the inner detector volume. The fourth Pixel Detector layer at the radius of 3.3cm will be added during the long shutdown 2013–2014 together with the replacement of the Pixel services.