GeV electrons due to a transition from laser wakefield acceleration to   plasma wakefield acceleration
  We show through experiments that a transition from laser wakefield acceleration (LWFA) regime to a plasma wakefield acceleration (PWFA) regime can drive electrons up to energies close to the GeV level. Initially, the acceleration mechanism is dominated by the bubble created by the laser in the nonlinear regime of LWFA, leading to an injection of a large number of electrons. After propagation beyond the depletion length, leading to a depletion of the laser pulse, whose transverse ponderomotive force is not able to sustain the bubble anymore, the high energy dense bunch of electrons propagating inside bubble will drive its own wakefield by a PWFA regime. This wakefield will be able to trap and accelerate a population of electrons up to the GeV level during this second stage. Three dimensional (3D) particle-in-cell (PIC) simulations support this analysis, and confirm the scenario. 
P. E. Masson-Laborde, M. Z. Mo, A. Ali, S. Fourmaux, P. Lassonde, J.   C. Kieffer, W.Rozmus, D. Teychenne, and R. Fedosejevs
physics.plasm-ph hep-ex