• ultra-short laser pulses
• radiation sources
• electron beams
• laser-plasma interaction

Plasma based particle acceleration is now regarded as a promising way to extend performance of existing accelerators as shown recently at SLAC where energy doubling of a fraction of the initial 20 GeV electron beam was successfully demonstrated using plasma wakefield acceleration. At the same time, a wide range of "all optical" (laser-driven) plasma accelerators have been developed leading to the production of electron bunches of multi-GeV, using laser-driven plasma wakefield acceleration (LWFA).
In fact, plasmas can support ultrahigh electric fields, of the order of 100 GV/m, more than three orders of magnitude higher than the highest gradients achievable with current RF acceleration technology.

Laser-plasma acceleration of electrons, first proposed in 1979 by Tajima and Dawson, became readily feasible when ultra-short laser pulses became available in the late 80's and currently is exploited in several laboratories worldwide to produce collimated (few mrad) and ultrarelativistic (hundreds of MeV to GeV) electron beams. The extremely wide range of applications of such laser-driven plasma accelerators includes the production of so-called "secondary sources" which include, for example, positron sources, gamma-ray sources and, in perspective, compact synchrotron radiation and free-electron laser sources. In this context, a laser-plasma acceleration programme has been established at ILIL-INO (CNR, Pisa) and more recently at Sparclab (LNF-INFN, Frascati), also in collaboration with the ASTRA-GEMINI laser at the Rutherford Appleton Laboratory (Oxford, GB). The programme is aimed at the development of new, all-optical, secondary radiation and particle sources for applications. My thesis work is centered on the study of the properties of LWFA generated electron beams in two experiments included in the above cited programme. After a preliminary brief introduction on LWFA and a focus on the most advanced acceleration regimes, a description of the experiments is given, with special attention to the laser and electron diagnostics dedicated to the characterization of beam quality. Beam properties have been retrieved using different diagnostics including a scintillating screen for studies of beam divergence and pointing stability, and a magnetic spectrometer based upon a permanent dipole, coupled to a scintillating screen, to retrieve the electron beam spectrum. Imaging of plasma emission perpendicular to laser propagation axis, was also detected to study laser propagation inside the plasma. Combining results of these different diagnostics, details on the acceleration process of the electrons are inferred. With the help of numerical particle-in-cell simulations, the acceleration mechanism occurring in our particular wakefield acceleration regime and its interesting feature are identified. The results on the properties of the accelerated electron bunch are then compared with the optimum values expected using available scaling laws for the so-called "bubble regime".