Thesis title: Design study of plasma targets for laser driven wakefield acceleration experiments
The strength of plasma-based accelerators is their compactness, thanks to the plasma accelerator modules, which have dimensions of the order of $cm$. The limitation of this type of acceleration lies in the difficult control of the characteristics of the plasma itself, and therefore in the synchronization between it and the particle beam to be accelerated. This issue has a major influence on the quality of the accelerated bunches.
In this work, a characterization conducted in the SPARC\_LAB (LNF-INFN) laboratories on some plasma targets, i.e. different nozzle geometries and different types of capillaries, is presented. The main goal of the work is the study and the realisation of the plasma guiding process of a laser pulse, inside a plasma-filled capillary discharge. This technique is necessary to increase the acceleration length and thus the energy gain of the accelerated beam, in the external-injection scheme of the Laser Wake Field Acceleration (LWFA). Plasma density is a characteristic of fundamental importance as it determines both the guiding and the acceleration process. Two different methods of plasma density measurement, interferometric and spectroscopic, are therefore reported. Preliminary studies of new techniques for the diagnostics of plasma inside channels and new schemes for the delivery/extraction of laser pulses inside capillaries are proposed. All topics covered include theoretical study, one-dimensional and/or fluid-dynamic simulations, and experimental data.