  The plasma-based acceleration is an encouraging technique to overcome the
limits of the accelerating gradient in the conventional RF acceleration. A
plasma accelerator is able to provide accelerating fields up to hundreds of
$GeV/m$, paving the way to accelerate particles to several MeV over a short
distance (below the millimetre range). Here the characteristics of preliminary
electron beams obtained with the self-injection mechanism produced with the
FLAME high-power laser at the SPARC_LAB test facility are shown. In detail,
with an energy laser on focus of $1.5\ J$ and a pulse temporal length (FWHM) of
$40\ fs$, we obtained an electron plasma density due to laser ionization of
about $6 \times 10^{18}\ cm^{-3}$, electron energy up to $350\ MeV$ and beam
charge in the range $(50 - 100)\ pC$.

Accelerator Physics;High Energy Physics - Experiment