Towards the construction of a new tracker for the ATLAS detector at the HL-LHC

This thesis work focuses on the upgrade of the ATLAS tracking system, known as ITk, for the High Luminosity period of the LHC. The thesis primarily focuses on two main aspects: the characterization of ITk Pixel End-Cap local supports and the characterization of ITk Pixel 3D modules. For the local supports, which provide mechanical stability and cooling to the Pixel detector in the Outer Endcap region, density distribution measurements of carbon foam blocks used in Half-Rings revealed homogeneity with a maximum dispersion of 13 percent. Thermo-mechanical property measurements confirmed compliance with deformation specifications, with absolute deformation variations less than 2 μm per degree. An effective detection study of anomalies in heat propagation within the local supports was conducted, ensuring reliability in identifying dysfunctions. Regarding the ITk 3D pixel modules, the characterization included the qualification of RD53A modules and pre-production modules. The RD53A modules demonstrated high hit efficiency both before and after irradiation, with hit efficiencies exceeding 96% and 98% after irradiation for different pixel pitches. The pre-production modules utilizing 3D sensors and ITkPixV1.1 readout chips showed excellent performance, achieving nearly 99% efficiency in the unirradiated configuration and 98.5% efficiency (99.9% for tilted modules) after irradiation.