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Since the laser invention [1, 2], the advent of Free Electron Lasers (FEL) [3, 4] in the X-ray domain half a century later, has opened new areas for matter investigation with higher temporal resolution. In parallel, the development of laser plasma acceleration (LPA) [5] that delivers today several GeV beam acceleration [6] in a short distance appears also very promising. The qualification of the LPA for FEL application can thus be viewed as an important challenge [7]. Nevertheless, present LPA electron beam parameters (e. g. energy spread and beam divergence) do not meet conventional accelerator state-of-the-art performance and FEL application requires a specific beam handling. In such a prospect, the COXINEL beam manipulation line [8, 9] using variable permanent magnet quadrupoles for emittance growth mitigation and de-mixing chicane for the energy spread handling developed at SOLEIL has been installed for using electrons produced with an intense laser of Laboratoire d’Optique Appliquee (LOA). Strategies for controlling electron beam position and dispersion have been elaborated and demonstrated [10]. Finally, undulator spontaneous emission has been measured at the end of the line.

The Photo Injector Test facility at DESY, Zeuthen site (PITZ), offers the unique possibility to study and demonstrate the self-modulation of long electron bunches in plasma. A set of numerical simulations with the particle-in-cell code OSIRIS has been carried out for a better understanding of the process. Of particular interest is the measurement of the energy modulation induced to the beam itself by means of the generated wakefields in plasma. It will reflect the key properties of the accelerating electric fields such as their magnitude and their phase velocity, both of significant importance in the design of experiments relying on this technique.