Electrons are accelerated up to 0.8 GeV in a self-injecting laser wakefield accelerator driven at a plasma density of 5.5 × 1018 cm−3 by a 10 J, 55 fs, 800 nm laser pulse in the blow-out regime. The electron beam stability is correlated with the laser focal spot pointing stability and depends on the target alignment. Variations of the laser pulse energy, focal spot size and energy within the full width at half maximum have little effect on the electron beam profile (stability) but impact the electron energy (stability). The peak electron energy is higher than expected for the initial vacuum intensity. This is evidence for intensity amplification which also explains the observation of polyenergetic beamlets.
Direct laser acceleration of electrons from a plasma mirror by an intense few-cycle Laguerre–Gaussian laser and its dependence on the carrier-envelope phase