Effect of the laser wavefront in a laser-plasma accelerator

A high repetition rate electron source was generated by tightly focusing kHz, few-mJ laserpulses into an underdense plasma. This high intensity laser-plasma interaction led to stable electron beams over several hours but with strikingly complex transverse distributions even for good quality laserfocal spots. Analysisof the experimental data, along with results of PIC simulations demonstrate the role of the laser wavefronton the acceleration of electrons. Distortions of the laser wavefrontcause spatial inhomogeneities in the out-of-focus laserdistribution and consequently, the laserpulse drives an inhomogenous transverse wakefield whose focusing/defocusing properties affect the electron distribution. These findings explain the experimental results and suggest the possibility of controlling the electron spatial distribution in laser- plasma acceleratorsby tailoring the laser wavefront.