Sviluppo di Ultra-Fast Silicon Detectors per il tracciamento in 4D ad High-Luminosity LHC: misure di laboratorio e simulazioni numeriche

The High Luminosity LHC (HL-LHC) is a major and extremely challenging upgrade of the present LHC, since it will be featured with a significant luminosity increase. In order to cope with its harsh environment, characterized by high pile up and radiation dose, the experiments require substantial upgrades. Specifically with regard to the CMS Detector, precision timing is necessary to preserve its efficiency, resolution and background rejection: for this reason a Minimum Ionizing Particle (MIP) Timing Detector has been planned to cover the barrel and the endcap regions. This thesis is thus centered on Ultra-Fast Silicon Detectors (UFSD), which have been chosen to be installed in the Endcap MIP Timing Layer of CMS. UFSD are thin sensors (∼50 µm) based on the LGAD technology, provided with a moderate internal gain (10-20) and optimized for timing. Their design allows to reach a time resolution of ∼30 ps and a spatial resolution of ∼10 μm and to withstand fluences up to 3×15 neq/cm2. A first part of this thesis work is focused on TCAD simulations, a fundamental tool in the development of UFSD productions; investigations regarding dead area, cross talk and radiation damage of UFSD have been performed with Sentaurus TCAD by Synopsys. Therefore, many fundamental properties of UFSD for successful timing measurements have been explored with comprehensive studies in the Laboratory for Innovative Silicon Sensors: among them, the most important regard uniformity of large sensor, effects of doping elements, radiation hardness and inactive area of the devices. Finally, some of these experimental data have been compared with simulation results.