An important limit for energy gain in laser-plasma wakefield accelerators is the dephasing length, after which the electron beam reaches the decelerating region of the wakefield and starts to decelerate. Here, we propose to manipulate the phase of the electron beam in the wakefield, in order to bring the beam back into the accelerating region, hence increasing the final beam energy. This rephasing is operated by placing an upward density step in the beam path. In a first experiment, we demonstrate the principle of this technique using a large energy spread electron beam. Then, we show that it can be used to increase the energy of monoenergetic electron beams by more than 50%.

Centro de Laseres Pulsados Parque Cientfico 37185 Villamayor Salamanca Spain

Czech Technical University Prague FNSPE Brehova 7 11519 Prague Czech Republic

Institute of Physics ASCR v v i ELI Beamlines project Na Slovance 2 18221 Prague Czech Republic

Laboratoire d'Optique Appliquée ENSTA ParisTech CNRS UMR7639 École Polytechnique Chemin de la Hunière 91761 Palaiseau France

Max Planck Institut für Quantenoptik Hans Kopfermann Strasse 1 85748 Garching Germany

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Laser based 100 GeV electron acceleration scheme for muon production