Issues with phase space characterization of laser-plasma generated electron beams

Plasma acceleration is the new frontier in particle beam accelerators. Using the strong electric fields inside a plasma it is possible to achieve accelerating gradients orders of magnitude larger with respect to current technologies. Different schemes, using completely different approaches, have been proposed and several already tested, producing beams of energy up to several GeV. Regardless of the technique used for acceleration a precise determination of the output beam parameters is mandatory for the fine tuning of the process. The measurement of these parameters, in particular the beam distribution in transverse and longitudinal phase space, is not trivial, mainly due to the large energy spread and to the tight focusing of these beams or to the background noise produced in the plasma channel. We illustrate the main problems related to the diagnostic of this kind of beams and some of the proposed or already realized solutions