Electron injection and acceleration into laser-driven wakefield from a solid overdense plasma target
A laser-plasma acceleration scheme combining electron extraction from a solid overdense target with wakefield acceleration in an adjacent underdense plasma region is presented. A laser pulse excites a diffracted electromagnetic wave at the overdense plasma interface, extracting and pre-accelerating electrons, which are then injected into laser-driven wakefield cavities in the underdense plasma. A parametric study identifies key conditions enabling efficient electron injection and energy gain in this two stage acceleration configuration. Two-dimensional particle-in-cell simulations performed with the Smilei code show that the proposed scheme produces electron bunches with a tunable trade-off between charge, energy, and beam quality at laser intensity $I_0 \lambda_0^2 \simeq 3.4 \times 10^{19}$ W$\mu$m$^2$/cm$^2$ ($\lambda_0=0.8 \mu$m). According to the parameters used, the electron beam is accelerated to peak energies of $\sim150-250$ MeV with an estimated charge in 3D of $\sim50-400$ pC integrated over the full width at half maximum energy range, and $\sim100-1800$ pC with energies above $50$ MeV.