Searches for Vector-like Quarks with the ATLAS Detector and Design of the Type-0 Services for the ITk Upgrade

The Standard Model (SM) of Particle Physics has enjoyed unprecedented success in describing the universe at the subatomic level. Yet, it must not be a complete theory of nature as it does not include gravity, cannot explain dark matter, provides no insight into huge hierarchies in forces and masses, and so on. Many extensions to the SM aimed at addressing these shortcomings predict the existence of a new type of particle called vector-like quarks (VLQs). This thesis presents the latest status of two searches for VLQs using the full Run 2 data set of 13 TeV pp collisions produced by the LHC and recorded by the ATLAS detector. The main focus will be on a new search for the pair-production of VLQs that each decay into a light SM quark and W boson. The second search targets top-partner VLQs produced in pairs, each VLQ then decaying to a W boson and b-quark. These represent the latest status of searches for VLQs with charged current decays with the current ATLAS detector. Looking to the future, the ATLAS detector will soon undergo an extensive upgrade in preparation for the High-Luminosity LHC, including installing a completely new, all-silicone tracking system called the Inner Tracker (ITk). This thesis highlights the development and design of the Type-0 electrical services for the all-new ITk Pixel tracking system that will lie at the heart of the upgraded ATLAS detector.