Phd in ACCELERATOR PHYSICS

Thesis title: Longitudinal beam coupling impedance mitigation studies for CERN PS accelerator complex

In the context of the High Luminosity Upgrade of the LHC (HL-LHC), the objective is to double the beam intensity in the injectors chain, including the Proton Synchrotron (PS). Consequently, the generation of high-quality beams with the highest possible intensities is essential. In preparation for this upgrade as well as future reliable particle acceleration, mitigation measures targeting the coupling impedance of the beam have already been initiated and are currently in progress. The objective of this research is to identify, model and mitigate impedance sources that could impede the achievement of these targets within the PS complex. This study characterize the longitudinal beam coupling impedance of existing and newly designed components of the accelerator, making use of electromagnetic simulation tools and radio frequency measurements. Special attention is paid to kicker magnets, which are a significant contributor to the overall PS beam impedance in terms of the broadband component. The aim of the study is the mitigation of the impedance sources that were identified as potentially driving longitudinal coupled-bunch instabilities in the low frequency range. Furthermore, the characteristics of other components that have already been installed in the PS accelerator complex, as well as those that are scheduled for installation, have been discussed. These include vacuum equipment, such as pumping manifolds, which have been identified as the primary source of instabilities in the high-frequency range. Moreover, this work incorporates the impedance of other critical components, such as septum magnets, which were previously excluded from the PS longitudinal beam coupling impedance model. This work presents a comprehensive understanding of the impedance sources and proposes a method for their mitigation. The impedance study is addressed by means of a combination of bench measurements and electromagnetic simulations.