Dottorato in FISICA DEGLI ACCELERATORI

Titolo della tesi: Beam Dynamics Studies for High Brightness Linear Accelerators

High brightness electron beams, such as those produced by radio-frequency (RF) photoinjectors, enable state-of-the-art applications in photon production and high-energy physics colliders. Examples of advanced applications in such fields include free electron lasers (FELs) as well as inverse Compton scattering (ICS) sources and high luminosity electron-positron linear colliders. Charged beams of this kind imply the coexistence of high peak currents, small transverse emittances and narrow energy spectra which results in a high six-dimensional phase-space density. Consequently, high brightness beams are strongly affected by the self-induced electromagnetic fields which cause interaction among charged particles through space charge and wakefields mechanisms. Such effects can be both present at significant levels in high gradient linear accelerators (linacs) and may dilute the beam quality with a negative impact on the applications. Therefore, in order to meet the demanding performance of such machines, thorough studies of the beam dynamics investigating all relevant effects, applied and collective, are required in order to predict the operational limits of a given machine. The research work presented throughout this manuscript investigates the combination of modern high brightness electron sources, relying on the use of high field rf photoinjectors, and high gradient rf linacs. A special emphasis is addressed to the hybrid gun developed as a driver for advanced light source applications. Commonly adopted models for the description of the beam dynamics in the form of transfer maps are reviewed in addition to the fundamental tools employed for collective effects. Useful semi-analytical models are investigated for the development of a custom tracking code describing the dynamics of charged particles in presence of space charge and wakefield effects. Several examples and applications concerning the cutting-edge projects endorsed in the framework of the collaboration with the University of California Los Angeles (UCLA) and its partners are discussed thoroughly. In addition, relevant aspects concerning the development of the infrastructures foreseen by such a collaboration are discussed. Examples of this class include the characterization and operation of accelerator components in the context of the experimental activities in the laboratory facilities.