Studies of a Digital SiPM and MAPS Prototypes as Key Technologies for Future High-Energy Physics Experiments

Abstract

Digital Silicon Photomultipliers (dSiPMs) and Monolithic Active Pixel Sensors (MAPS) are emerging technologies, fabricated using commercial Complementary Metal-Oxide-Semiconductor (CMOS) processes. These detectors have the potential to become key components in High-Energy Physics (HEP), with the ability to meet the demanding requirements of future experiments. <br /> The first part of the thesis analyzes the DESY dSiPM prototype as an example of the technology potential. Extensive laboratory characterizations confirm the functionality of the sensor and of all integrated CMOS circuitry. Sensor calibrations ensure stable and controlled operation enabling the study of prototype performance by offering an in-depth understanding of the sensor’s capabilities. The performance of the prototype in Minimum Ionising Particles (MIP) detection is evaluated through beam tests at the DESY II test-beam facility. The measurements aim to establish the potential use of this technology in 4D-Tracking of charged particles. The bare DESY dSiPM in MIP detection shows a spatial resolution of 20 µm, a time resolution of 50 ps with an efficiency of about 30 %, limited by the fill-factor characteristic of the technology. A novel detector-concept is therefore introduced that combines dSiPM with thin Cerium-doped Lutetium Yttrium Orthosilicate (LYSO(Ce)) radiators to overcome these efficiency limitations. This approach improves detection efficiency over 99 %, and enables better discrimination of signal events. The results presented support the potential use of dSiPM in MIPs 4D-tracking applications. <br /> The second part of this thesis focuses on MAPS technology, analyzing two prototypes developed using a 65 nm CMOS process. The first sensor, DESY Chip V1, is designed to verify the performance of a fast Charge Sensitive Amplifier (CSA), characterized in laboratory and test-beam. The studies confirm the functionality of the circuits while highlighting some limitations that contributed to design improvements in later versions. Several Analog Pixel Test Structure (APTS) prototypes are also studied in collaboration with CERN and the ALICE IT3 group. The operational parameters of the sensors are optimized and charge calibrations are performed. The study of the performance in MIP detection of an APTS prototype with a pixel pitch of 15 µm demonstrates spatial resolutions of less than 3 µm and detection efficiencies higher than 99 % with low noise occupancy in a wide operational window. The results presented support the potential of MAPS technology in meeting the stringent requirements of future experiments, particularly for vertex detectors in future lepton colliders.