• focusing
• hot electrons
• laser
• microlenses
• plasma
• proton radiography
• return current
• TNSA
• transient charging
• ultrafast

The experiment described in the thesis is meant to investigate the propagation of an ultrafast return current developed on a laser-irradiated gold foil and propagating along a metallic wire connected to it. The foil charging is due to the permanent escape to vacuum of a fraction of highly energetic laser-accelerated hot electrons from the target surface. The proton beam produced via TNSA mechanisms is employed in a time of flight arrangement to diagnose the transient positive charge induced along the wire on a radiochromic film stack. The current strength, duration and velocity are inferred from the experimental data and simulation codes. The analysis is crucial to develop a new target geometry designed to obtain a chromatic focusing of the laser-driven proton beam, which is of main importance for several future applications. The laser-driven micro-lens functioning and manufacturing procedure are also addressed in the thesis.