The ability to rapidly identify the source of emittance blow-up in the CERN Proton Synchrotron (PS) is crucial to ensure the good operation of the Large Hadron Collider (LHC) and its successor the High Luminosity LHC (HL-LHC). Such ability requires to continuously and non-destructively measure the beam size. However, the beam transverse diagnostics in the PS are currently performed by Beam Wire Scanners (BWS) and Secondary Emission Monitor (SEM) grids. Both of these systems provide high-quality measurements of the beam transverse size. Nonetheless, the destructive nature of their measurement method limits their use to single-shot measurements during the beam commissioning. For this reason, the installation of a new Beam Gas Ionisation (BGI) profile monitor was proposed for the PS. The new PS-BGI infers the beam profile from the transverse distribution of electrons created by the ionisation of rest gas molecules by the high energy beam particles. The distribution is measured by accelerating the electrons onto an imaging detector based on Timepix3 Hybrid Pixel Detector (HPD). This measurement method allows for continuous, non-destructive beam size measurement. Moreover, the extreme sensitivity of Timepix3 HPDs allows foregoing the use of a gas injection system, while permitting to record the beam size at several kilo-Hertz. This thesis covers the development of this new PS-BGI, from early concept and simulation to the installation and commissioning of a prototype in the PS. This prototype demonstrated the first successful use of Hybrid Pixel Detectors (HPD) in the primary vacuum of an accelerator at CERN. The performances of the prototype were characterised and the first continuous beam profile measurements of the LHC-type beam in the PS were recorded.
