Electron acceleration by a two stage laser-plasma interaction

Ultraintense, short pulsed lasers with high contrast allow the exploration of new mechanisms for particle acceleration. In particular, when such lasers irradiate an overdense plasma, electromagnetic waves appear at the vacuum-plasma interface, enabling local field confinement and enhancement. Since these mechanisms involve an overdense plasma, high values of total electron beam charge ( nC) can be achieved, which is important for applications in the fields of plasma-based accelerators, electron sources, among others. Recent Particle-in-Cell (PIC) simulations analyzed a laser pulse interacting with the wedge of an overdense plasma, and showed that it produces a diffracted electromagnetic wave with an intense longitudinal electric field that efficiently accelerates collimated electron bunches with high charge ( nC) and relativistic energies up to 130 MeV. In this talk, I will present a new scheme which couples electron acceleration in an overdense plasma with the wakefield produced by the laser propagating through an underdense plasma. Highly charged electron bunches are emitted from the overdense plasma, and trapped by the wakefield in which they are accelerated even further. Such a scheme enables us to obtain highly charged and highly energetic electron bunches at the end of the second acceleration stage.