Proof-of-principle experiment for nanoparticle-assisted laser wakefield acceleration

In the present work, we demonstrate for the first time a proof-of-principle experiment for nanoparticle-assisted laser wakefield acceleration. The nanoparticles, generated through laser ablation of aluminium, were introduced into the plasma and used to trigger the injection of electrons into the nonlinear plasma wake excited by a high power femtosecond laser. In this experiment, a significant enhancement of the electron beam energy, energy spread and divergence is obtained compared with the case when electrons are self-injected. The best quality electron bunches presented peak energy up to 338 MeV with a relative energy spread of 4.7% and vertical divergence of 5.9 mrad. This method can be further improved by adding an aerodynamic lens system, for instance, which would control the nanoparticle size, density, material and injection position thus allowing accurate control of the laser wakefield accelerator.