Phd in ACCELERATOR PHYSICS

Thesis title: Experimental and theoretical development of m-scale and high repetition rate plasma sources for plasma-based particle accelerators

Novel plasma-based particle accelerators allow a drastic reduction in size and cost, compared to conventional RF-based structures, due to strong accelerating and focusing fields established inside plasmas. A key role in the development of plasma-based accelerators is played by plasma sources. Indeed, the design of specific devices able to produce stable and uniform plasma channels is crucial for the efficiency of the plasma acceleration mechanism. The development of plasma sources is particularly focused on the realization of m-scale devices, able to generate stable and long plasma channels for high energy gain acceleration. Furthermore, the longevity of plasma sources is a key aspect for long-term operation at high repetition rate, which is a fundamental requirement for many particle accelerator applications. In this context, this PhD thesis presents the design and development of m-scale and high repetition rate plasma sources for plasma-based particle accelerators. Experimental and theoretical activities are carried out at Plasma_lab laboratory, located at National Laboratory of Frascati (LNF-INFN), and in the framework of EuPRAXIA@SPARC_LAB project, with special focus on plasma discharge capillaries, in which plasma channels are created by means of high voltage pulses. Experimental and numerical studies are performed to investigate the effect of the capillary geometry on the plasma density distribution, aimed at improving the plasma density modulation required for efficient plasma acceleration. Novel schemes are designed and tested for the realization of compact and cost-effective m-scale plasma discharge capillaries, able to provide high energy gain acceleration, staged focusing-acceleration and guiding of charged particle beams. Moreover, high repetition rate tests are performed with innovative ceramic capillaries, assessing the ability of adopted materials to withstand the heat load produced by high voltage plasma discharges. In addition, laser-induced plasma filaments are studied and characterized as an alternative plasma source for high repetition rate applications. In conclusion, a preliminary design and test of a 60 cm-long capillary, conceived for the plasma module of EuPRAXIA@SPARC_LAB project, is presented.