The ALICE silicon pixel detector system

The ALICE Silicon Pixel Detector (SPD) will constitute the two innermost layers of ALICE, and will due to its high granularity provide precise tracking information. In heavy ion collisions, the track density could be as high as 80 tracks / cm2 in the first SPD layer. The SPD will provide a spatial resolution of around 12 μm in the rφ-direction. The results presented in this thesis illustrate the measurements performed in order to characterize the detector performance and qualify components for inclusion in the detector and depicts the work carried out needed for the production phase of the SPD. Quality assurance criteria and test procedures have been developed and fine-tuned for the different components of the SPD. The tests involved visual inspection, electrical tests as well as measurements using a radioactive source. Pixel planes were studied in a heavy ion beam as well as in a proton/pion beam. A new tracking algorithm for the unfocused proton/pion beam data taking the tilt and the azimuthal angle into account was developed. Further, a study of the cluster sizes as function of different operating parameters, i.e. threshold, and track incidence angle was performed giving a comparison between two sensor thicknesses (200 μm and 300 μm). A test system based on a pulsed infrared laser was established in order to test SPD assemblies and the FastOr signal generated by the pixel chip. This laser allowed for the first time a complete characterization of the working point and performance of the chip internally generated FastOr signal. Furthermore, the setup allowed a detailed study of the ALICE1LHCB chip characteristics with well defined timing and energy deposition in the silicon sensor. The laser measurements on ALICE assemblies could directly be compared with the results of the beam test 2002 and 2003. During my doctoral thesis at CERN, I have developed and applied test criteria for the SPD components. Furthermore, I developed an infra-red laser test system which allowed a detailed study of the detector performance, a special cluster size study and the functionality of the FastOr signal. The cluster size studies obtained with the laser measurements are compared with the results from the beam test data taken in high energy particle beams. (author)