Development of 3D Diamond Detectors for Particle Physics and Dosimetry

Abstract

3D diamond detectors are made by inscribing vertical electrode columns in the bulk of the material. In this work, the electrodes are made by focusing a femto-second laser inside the crystal to create graphitic paths. The processing of the columns has been optimised with dynamic adaptive optics, using a Spatial Light Modulator (SLM). Control of the processing with an SLM has led to new design features in 3D diamond detectors, such as implementing horizontal electrodes inside the bulk and use of graphitisation in place of conventional surface metal. The thesis demonstrates the applications in the advancements of 3D diamond detector design for specific applications and outlines the motivations for the future viability of full scale 3D diamond devices. Prototype 3D diamond detectors have been designed to meet the specifications for the upgrade of the ATLAS diamond beam conditions monitor for the high luminosity LHC. The horizontal connections reduce the volume of low field regions inside the bulk of the device and provide a level of redundancy. Structures were fabricated with both cubic and hexagonal 3D cell shapes. The prototypes structures were tested using particle beams. The tested device showed charge collection efficiency consistent with $100~\%$ and improved uniformity in response between the front and back side of the detector relative to previous 3D diamond detectors with only vertical electrodes. Diamond is of interest to medical dosimetry as it is a material closer to body tissue equivalence than other available detector substrates. A 3D diamond dosimeter prototype with surface graphitisation in place of conventional metallisation was tested. The dosimeter tested is completely carbon based, apart from the connections beyond the metallic wire bonds. This device showed response linear with dose rate in both laboratory and clinical dose ranges. The fabrication parameters for laser processing have been studied, evaluating the importance of the use of the SLM in fabricating columns for detector use. The laboratory set-up available at the University of Manchester has been qualified in this work to produce horizontal and vertical graphitic paths.

Date of Award	1 Aug 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Alexander Oh (Supervisor) & Justin Evans (Supervisor)