# Characterization of CMOS sensors for particle physics applications

Freeman, Patrick (2022). Characterization of CMOS sensors for particle physics applications. University of Birmingham. Ph.D.

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## Abstract

This thesis summarizes work on the development of silicon sensor technologies for use in high energy physics experiments. This work has been focused on the characterization of passive strip sensors for hybrid devices as well as two novel monolithic active pixel sensors (MAPS) in the TowerJazz 180 nm CMOS imaging sensor process, MALTA and DECAL, for experiments at particle colliders. The MALTA sensor is part of a development towards a CMOS sensor based vertex detector system for use as a further upgrade by the ATLAS experiment, and the DECAL device is a more generic development suitable for use at either e$$^+$$e$$^−$$ or hadron colliders as an ultra high granularity electromagnetic calorimeter. The work has served to demonstrate the performance and identify shortcomings of the latest versions of these devices in the context of high energy particle physics experiments. Passive strip sensors for hybrids in the ATLAS Inner Tracker (ITk) were irradiated at the MC40 cyclotron in Birmingham and characterized. While the characterization results with devices irradiated at Birmingham were not conclusive, the sensor performance demonstrated at other facilities is within specifications, and the work has served as part of the commissioning of the irradiation facilities at Birmingham for sensor Quality Assurance during pre-production and production, and has highlighted issues to be resolved. Both monolithic pixel sensors, DECAL and MALTA, are the subject of ongoing developments to be included in future experiments. The very latest versions of MALTA were shown to be fully efficient after irradiation to 1×10$$^{15}$$ n$$_{eq}$$/cm$$^2$$ and nearly fully efficient at 2×$$^{15}$$ n$$_{eq}$$/cm$$^2$$, a significant improvement after having 78 % efficiency at 1×$$^{15}$$ n$$_{eq}$$/cm$$^2$$ in the original version of the device. Simulation for inclusion of calorimeter constructed from monolithic active pixel sensors (MAPS) in experiments shows promise to improve particle reconstruction with Particle Flow techniques. Measurements with the DECAL sensors have demonstrated the counting logic and digital configuration necessary for the proposed application in calorimetry. While both DECAL and MALTA would have to be subject to further design iteration for inclusion in experiments to improve the front-end, sensor, and readout characteristics, the demonstrated improvements show there is a clear path towards their final implementation.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Supervisor(s):
Supervisor(s)EmailORCID
Gonella, LauraUNSPECIFIEDUNSPECIFIED
Allport, Philip PatrickUNSPECIFIEDUNSPECIFIED