Test beam studies of pixel detector prototypes for the ATLAS-Experiment at the High Luminosity Large Hadron Collider

The upgrade of the Large Hadron Collider (LHC) in the mid-2020’s to the High Luminosity Large Hadron Collider will provide large amounts of data, enabling precision measurements of Standard Model processes and searches for new physics. This will also maximise the physics potential of the experiments located at the LHC. In order to record the desired inte- grated luminosity, the ATLAS detector will face challenges regarding the radiation damage, pile-up and amount of data. To cope with those challenges, the entire tracking detector is replaced by the new Inner Tracker, ITk. In order to develop novel detector modules, test beam measurements are a crucial tool to study and understand new read-out chips, novel sensor technologies, as well as the effect of radiation on the sensor and read-out chip. Not only in the R&D-phase but also in the phase of module production, test beams need to play a necessary role in the continuous quality assurance procedure. This thesis is focused on the test beam measurements of pixel modules for the ITk upgrade. Several aspects of test beams are covered and have been improved. Modifications to one of the used DAQ systems at test beams (USBpix) have been made. A new measurement technique using the USBpix system to make so-called in-time measurements at test beams has been developed. The measurement method as well as results from such a measurement are discussed in this thesis. Furthermore, many parts of the reconstruction framework have been modernised and improved. The track fit based on the General-Broken-Line algorithm now allows track reconstruction together with ATLAS pixel modules. Also, test cases were implemented to ensure long-term stability, and guarantee a consistent reconstruction, even in future versions. Additionally, a Monte Carlo framework was expanded to enable validation of the reconstruction algorithms.