Laser wakefield acceleration by petawatt ultrashort laser pulses

Abstract

An ultra‐short (about 30 fs) petawatt laser pulse focused in a wide focal spot (about 100μm) in rarefied plasma (n0 ∼ 1017cm−3) excites a nonlinear plasma wakefield which can accelerate injected electrons up to a GeV energy without pulse channelling. In these conditions, the laser pulse with an over‐critical power for relativistic self‐focusing propagates as in vacuum. The nonlinear quasi‐plane wake plasma wave, whose amplitude and phase velocity vary along the laser path, effectively traps and accelerates injected electrons with a wide range of initial energies. Electrons accelerated along two Rayleigh lengths (about eight centimeters) gain the energy up to 1 GeV. In particular, the electrons trapped from quite a long (τb ∼ 330 fs) non‐resonant electron beamlet of 1 MeV particles eventually form a low emittance bunch with the energies in the range 900 ± 50 MeV. All these conclusions follow from the two‐dimensional simulations performed in cylindrical geometry by fully relativistic time‐averaged particle code WAKE.