Design study of plasma targets for laser driven wakefield acceleration experiments

In this work, a characterisation 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.