Detailed studies of the ATLAS pixel detectors

Results are reported from beam tests of prototype Si pixel sensors and front-end electronics with analog readout developed for use in the ATLAS experiment at the Large Hadron Collider (LHC). Both irradiated and unirradiated assemblies were tested for charge collection, efficiency and position resolution measurements. These indicate that n⁺ in n silicon pixel detectors with p-spray isolation can operate after irradiation to fluences of up to 10¹⁵ n_eq/cm² without significant degradation in performance. The depletion depth of irradiated sensors was measured and their behaviour in a magnetic field was studied. The Lorentz angle was found to decrease significantly after irradiation. Comparison between performance on spatial resolution obtained with digital or with analogical readout is also presented