PIC Simulation Evidence for Ultrarelativistic Electron Bunches Produced by Non-Linear Laser Wakefield Acceleration

The interaction of very short (tens of femtoseconds) and ultraintense (I > 10¹⁸W/cm²) laser pulse on a low density-plasma (n_e ~ 10^-3 - 10^-2n_c, being n_c the critical density of the plasma at the laser wavelength) can generate longitudinal electron plasma waves with very large amplitude (wake-field generation process). The evolution of such a wake field is higly nonlinear and a lot of interesting phenomena occur, one of them being the trapping and acceleration of electrons of several MeV's in few tens of micrometers. The process of acceleration of the relativistic electrons in the regime of "Laser Wake Field Acceleration" has been demonstrated experimentally by using both gas-jet and (very recently) explodingfoils techniques. Here we present the result of a full 3D Particle-In-Cell (PIC) simulation of the interaction of a 35fs at relativistic intensity I = 10¹⁹W/cm², focussed onto a plasma having density equal to the "resonant" density n_R, which depends on the pulse length. The results of the PIC simulations agree with experimental data and confirm the production of a highly collimated and energetic electron bunch.