During the current long machine shutdown of the Large Hadron Collider (LHC) at CERN (Geneva), the innermost part of the ATLAS experiment, the pixel detector, is upgraded. The existing ATLAS pixel system is equipped with silicon sensors, organized in three barrel layers and three end cap disks on either side. To cope with the higher instantaneous luminosity in the future and for compensation of radiation damages due to past and near future running time of the experiment, a new fourth pixel detector layer is inserted into the existing system. This additional pixel layer is called “Insertable b-Layer” (IBL).
The IBL is a detector system, based on silicon pixel sensors. Due to the smaller radius, compared to all other detectors of the ATLAS experiment, it has to be more radiation tolerant, than e.g. the current pixel layers. Furthermore, a reduced pixel size is necessary to cope with the expected higher particle flux. During the planning phase for the IBL upgrade, three different sensor technologies were competing, namely 3D silicon sensors, planar silicon sensors and diamond sensors. For each of the two kinds of silicon sensor approaches, different design alternatives were taken into account as IBL candidates. To find the best sensor for the IBL upgrade, a series of testbeam measurements were performed at DESY (Hamburg) and CERN. This thesis describes the used testbeam setup, the testbeam analysis tools and the results of the IBL testbeam that finally led to the sensor technology choice for the Insertable b-Layer.
