MACHINE COMPONENTS IMPEDANCE CALCULATION AND BUTTON TYPE BEAM POSITION MONITOR DESIGN FOR THE ELETTRA 2.0 SYNCHROTRON LIGHT SOURCE

The third-generation Italian synchrotron radiation facility Elettra has been serving the national and international scientific and industrial communities since 1994. Over the time many improvements were made in order to keep the machine updated and therefore competitive with other more recent light sources. Aimed to significantly enhance the characteristics of the generated X-ray beams, an upgrade project, approved by the Italian Government in 2017, is ongoing at Elettra Sincrotrone Trieste for a diffraction-limited fourth-generation storage ring light source called Elettra 2.0. Elettra 2.0 will be an ultra-low emittance light source providing high brilliance and coherence, with the option to produce very short pulses for time resolved experiments using superconducting deflecting cavities. This thesis, developed in the context of the Elettra 2.0 project, covers two topics involved in the design of any kind of particle accelerator: 1. wakefields and beam coupling impedances; 2. beam position monitor devices; The first topic, that represents a critical aspect of any particle accelerator, describes the electromagnetic interaction between the circulating beam and its surrounding environment, and directly affects the stability of the photon beams emitted by the machine. A careful electromagnetic evaluation of each component of the vacuum chamber that “sees” the beam has always to be performed in order to evaluate its effect on the global machine impedance budget. In this work, after a general review of wakefield and impedance concepts, an estimation of the wakefield effects due to the joints located between different sections of the vacuum chamber is performed. Two types of joints have been examined through numerical analysis, and the corresponding impedance contribution have been compared taking into account different gap thicknesses. The second topic, which on some aspects is a sub-set of the first one, takes into account the electromagnetic mechanism that allows the detection of the transverse position of the beam in dedicated location along the machine. Moving from a theoretical characterization of the common round geometry, rhomboidal structures are studied through a careful numerical analysis relying on advanced computer-aided tools. Several critical elements, such as wakefields, pick-up signal extraction, and trapped and propagating modes, are explored from the simulation point of view and from the experimental one, by deploying a manufactured microwave test bench, which is employed to measure the radio frequency behavior of a BPM prototype built at Elettra Sincrotrone Trieste. The aim of the proposed study is to identify a satisfactory tradeoff between achievable performance and practical realizability for BPM devices operating in last-generation light sources.