Dottorato in FISICA DEGLI ACCELERATORI

Titolo della tesi: Design and Optimization of Radio-Frequency Pulse Compressor Systems for High Brightness Linacs

Linac driven free electron lasers (FELs) are useful devices for studying matter so the demand for new FEL facilities is increasing constantly. The main issues of such machines are the size and the costs. Active research is going to improve the performance of the devices, reduce building and operational costs, and make them more compact. In this framework, the INFN project EURPRAXIA@SPARC_LAB, is a proposal to upgrade the SPARC_LAB test facility(at LNF, Frascati) to a soft X-ray user facility based on plasma acceleration and high-gradient X-band accelerating structures [65]. Also the European project CompactLight-XLS [53] aims to design a compactFEL for users, in the hard X-ray range using the X band technology in the hard X-ray range using the X band technology combined with a new C-band high-brightness photoinjector and innovative short-period undulators. In this thesis, the rf and thermo-mechanical design of the rf pulse compressor to be used in the X-band accelerating module, has been performed. The innovative design is based on the use of special gaskets with a reduction of the cost. In chapter 1, traveling wave structures are briefly introduced with their main parameters. In chapter 2, the EURPRAXIA@SPARC_LAB and CompactLight-XLS projects are briefly described with their applications, goals, and main components. In chapter 3, the use of the RF pulse compressor systems in LINAC is illustrated and the different adopted solutions are briefly summarized with particular details on the Barrel Open Cavity (BOC) solution. In chapter 4, the advantages of the new brazeless technology recently developed at LNF-INFN, for the realization of rf guns are briefly summarized and the opportunities to fabricate BOC pulse compressors systems with this new approach are put in evidence. Chapter 5, is the core chapter of the thesis in which I describe the work done to completely design the BOC cavity. The work flow involves the following main steps: • Analytical and numerical analysis and design of the BOC • Electromagnetic design and simulations • Sensitivity study due to mechanical errors and possible tuning • Thermo-mechanical analysis and design of the cooling channels. • Final mechanical design of the structure The conclusions and perspectives are reported in the last chapter 6.