Study of Silicon Pixel detectors for the ALICE tracker upgrade

The ALICE collaboration at CERN has planned to install a new vertex detector (ITS3) during the LHC Long Shutdown 3 (LS3) to replace the innermost three layers of the present Inner Tracking System (ITS). This novel vertex detector, consisting of curved wafer-scale ultra-thin silicon sensors arranged in perfectly cylindrical layers, is presently under development. It will provide a large reduction of the material budget in the region close to the interaction point and a large improvement of the tracking precision and efficiency at low transverse momentum. The activity for this thesis consisted in the characterization of some pixel test structures exposed to different levels of radiation to understand how the most important characteristics of the sensors - namely charge collection efficiency, speed, noise, etc. - degrade after irradiation. This type of characterization is essential, since one of the main requirements for pixel sensors for future high luminosity runs is high radiation hardness.