Commissioning and Alignment of the ATLAS Inner Detector Using Cosmic Data

The ATLAS experiment is one of the two general purpose detectors at the Large Hadron Collider. ATLAS is equipped with a charged particle tracking system built on three subdetectors, which provide high precision measurements made from a fine detector granularity. The pixel and microstrip subdetectors, which use the silicon technology, are complemented with the transition radiation tracker. The ATLAS detector is operational since 2008 and more than ten million cosmic tracks have been collected in 2008 and 2009. These data are used for the commissioning of the experiment. The current status of the Pixel, SCT and TRT detectors will be reviewed. We will report on the commissioning of the detector, including overviews on services, connectivity and observed problems. Alignment constants are calculated and the detector is calibrated. The required precision for the alignment of the most sensitive coordinates of the silicon sensors is just a few microns. The outline of the alignment algorithm and its implementation of the alignment software, its framework and the data flow will be discussed. The calibration of the silicon subdetectors, like the determination of the lorentz angle, is presented. The overall performance of the charged particle tracking system is studied.