Ph.d. degree
IFCA, Spain

Clara Lasaosa García

Supervisor: Prof. Gervasio Gomez Gramuglio, Prof. Jordi Duarte Campderros

Keywords:

• Hybrid detectors
• Radiation-hard detectors
• Timing detectors
• Particle tracking detectors (Solid-state detectors)
• Large detector systems for particle and astroparticle physics

Abstract:

The upcoming high-luminosity phase of the CERN Large Hadron Collider (LHC) imposes stringent requirements on the Compact Muon Solenoid (CMS) experiment, which must operate under unprecedented radiation levels and collision rates. To maintain high performance in such demanding conditions, the tracking system will be completely replaced. The upgraded system requires sensors that combine high radiation tolerance, minimal power dissipation, increased granularity to improve spatial resolution, and high single-hit detection efficiency. While planar silicon pixel sensors will be installed throughout most of the inner tracking system, 3D pixel sensors are the only viable option for the layer closest to the interaction point, owing to their superior radiation hardness and lower power dissipation.

This thesis presents the characterization of 3D pixel sensors—interconnected with full-size prototype readout chips—and their qualification for deployment in the upgraded CMS tracking system. The performance of these detectors was evaluated in test beam experiments before and after irradiation. The results demonstrate that 3D pixel sensors meet the CMS requirements, confirming their suitability for installation in the innermost layer of the tracking system.

System-level tests were also performed to fully validate the pixel detectors developed for the upgrade. In particular, their performance and specific functionalities of the readout chip were assessed under the power distribution scheme planned for the inner tracking system. Additionally, following a successful qualification program, initial quality control tests of the sensor-readout interconnects were carried out, marking the beginning of the production phase at one of the designated assembly centers.

Beyond the high-luminosity LHC upgrade, 3D pixel sensors are also being explored for timing applications in next-generation experiments, where high radiation tolerance and precise time resolution are required. This thesis investigates their timing performance, with particular focus on the effects of electric field non-uniformities and the influence of pixel cell geometry. Laser-based measurements reveal a significant impact of pixel cell layout, highlighting the importance of sensor design optimization for future timing applications.