New Generation Fast Silicon Detectors for Timing and Particle Identification: High Energy Physics and Applications

Abstract

The High Energy Physics (HEP) community is working towards the upgrade of existing research facilities, as well as paving the way for the construction of state-of-the-art particle colliders. The increased rate of collisions per bunch crossing poses a great challenge in preserving the reconstruction capabilities of the experiments. This situation has constituted a breeding ground for the development of particle detectors specialized in reconstructing the time coordinate of events with great accuracy. This thesis presents the results obtained from the characterization and optimization of Low Gain Avalanche Detectors (LGADs) designed for the End-Cap Timing Layer (ETL) of the Compact Muon Solenoid (CMS) experiment. Together with the Barrel Timing Layer (BTL), the ETL will be part of the new MIP Timing Detector (MTD) of CMS and will require the installation of radiation resistant detectors capable of maintaining great timing resolution until the end of their expected life-cycle. During the tests performed at the Fermilab facilities, the performance of the detectors were investigated as a function of the irradiation received. The work of analysis pursued put on display the timing capabilities of these devices, showing a uniform response and total efficiency of the tested LGADs. The time resolution of the detectors was found to be consistent with the nominal specification required from the MTD, with values ranging from 30ps for non irradiated sensors, to about 50ps for sensors irradiated to a fluence of 10¹⁵n_eq. The timing technology of new generations has been extended well beyond the interests of particle physics experiments and embraces a number of different commercial and technical applications. In addition to the studies of LGADs for HEP experiments, this thesis describes the original contributions to two projects that employ the use of timing detectors, fast electronics, and reconstruction techniques. A description of the results obtained from an LGAD-based detector for beam monitoring of a medical linac, used for cancer treatments and diagnostics, is presented. This work exploits the synergies between HEP experiments and medical physics for addressing the demand for fast dosimetric devices. The tests performed in collaboration with the University College of Dublin (UCD), and the Saint Luke’s Hospital of Dublin, Ireland, proved unprecedented single particle resolution capabilities in radiation dense environments. The data analysis show the detector's linear behavior in charged particles counting up to about 100 MHz, with a time resolution of about 50ps. This information was used to characterize the beam temporal profile. It also allowed for the first ever reconstruction of a medical linac pulse sub-structure, revealing a characteristic oscillation frequency of about 3.2 GHz. The last section of this thesis presents the Advanced enerGetic Ion eLectron tElescope (AGILE) project. AGILE exploits the capabilities of fast read-out electronics, and sampling techniques typically employed for the development of timing detectors to perform real-time on-board particle identification in space. The project aims in discriminating and identifying the contribution of ions (form H-Fe) in a wide range of energies (1-100MeV/nuc) employing novel Pulse Shape Discrimination (PSD) techniques, with the sole use of silicon sensors. A prototype of the detector was designed, assembled, and tested using radiation sources at the KU facilities. The studies of the main key features for particle identification are consistent with the simulated performance, showing an overall energy resolution between 5.1% and 3.5%. The results are within the minimum standards required by AGILE for correct identification, of about 10%.