High-brightness beams for advancing light sources

This thesis investigates the generation and preservation of high‐brightness electron beams for advanced radiation sources, with applications ranging from compact inverse Compton facilities to large‐scale free‐electron lasers (FEL) and plasma‐based accelerators. The work aims to identify and mitigate the main physical mechanisms that limit beam quality during acceleration and compression, combining analytical modeling, numerical simulations, and machine design studies. The first part focuses on the BoCXS inverse Compton source, a proposal for a compact dual‐interaction‐point facility driven by a high‐gradient C‐band linac. Start‐to‐end simulations demonstrate the production of stable, low‐emittance, and low‐energy‐spread beams, and introduce optics strategies to preserve brightness through the switchyard and into the interaction region, ensuring tunable X‐ray emission in the 0.1–1 MeV range. The second part addresses the microbunching instability in the context of FEL facilities, such as FERMI and EuPRAXIA@SPARC_LAB. Using a semi‐analytical approach based on the Huang–Kim formalism, we study instability growth under different machine configurations and compression schemes, aiming at maximizing the beam quality required for FEL operation. In the end, we also present a theoretical outline of a laser heater, designed to ensure full compatibility with all EuPRAXIA@SPARC_LAB operation modes. The results highlight the importance of a model‐driven approach to accelerator design, while the methods and tools developed here provide a framework for optimizing brightness preservation across future light sources.