Test beam performance of the ATLAS Pixel Detector modules

The ATLAS Pixel Detector is the innermost tracking system of the ATLAS experiment at the Large Hadron Collider. The performance of several production modules of the ATLAS Pixel Detector was studied with a 180 GeV/c pion beam at the CERN SPS accelerator. Some of these modules were previously irradiated using 24 GeV/c protons up to the full LHC fluence of 1015 1 MeV neq cm−2 and a total ionizing dose of 500 kGy.A summary of data on the sensor properties, effective depletion depth, charge collection efficiency and trapping is given. Emphasis is put on the effect of timewalk in the optimization of detection efficiency and spatial resolution. The detection efficiency as a function of the beam intensity has been measured with a high intensity beam providing the expected occupancy at the nominal LHC luminosity.