Dottorato in FISICA DEGLI ACCELERATORI

Titolo della tesi: Study of Novel Devices for Compact Accelerating Structures

Recent developments in high gradient acceleration and compact electron linacs have demonstrated the capability to reach relatively high electron beam energy in a small space by considering the budget and realization issues. In this context, it is also necessary to manufacture and operate other accelerator components while maintaining a small accelerator footprint but without compromising the final performance. In this thesis, two of these components were studied; wakefield monitors (WFMs) and radio frequency (RF) compact loads. Both components have been designed and developed as part of the Compact Linear Collider (CLIC) study and work in X-band. The capability to measure accurately and correct the position of the beam with respect to accelerating structures is crucial for the accelerator studies to reach aimed design parameters. The WFM feasiblity experiments with beam have been going on for a while at the CERN Linear Electron Accelerator for Research (CLEAR) facility at CERN. The simulations and WFM signal analysis were performed to explore the possible reasons of the minimum position differences of the two wakefield modes measured during the experiments. The results were obtained as the combined effects of the antenna location, total charge per bunch, position jitter along the train and the asymmetric attenuation on the WFM data acqusition chain. The use of WFMs as a beam position instrumentation requires careful design and very tight control of the acquisition chain while expectancies need to be revised against realistic conditions and beam control. In the second part of the thesis, the compact RF spiral load was studied. It is one of the common components in accelerator studies based on traveling wave type linacs and drives the cost accordingly. The last iteration in this design is the optimization of the internal waveguide of the load to allow stackable design to decrease material loss and increase cost savings. A new generation of spiral, dry loads have been designed by alternating between RF and mechanical parametric load models. After additive manufacturing of the prototypes from two different vendors, low-power RF tests were performed and compared to the ideal case. In general, the new generation loads work with similar parameters as the old generation and reflection values well below -20 dB. However, some considerations need to be taken into account when working with additive manufacturing technology like final roughness, remaining dust or material choice. Keywords: Wakefield monitors, Additive manufacturing, RF design, optimization, X-Band