Experiments and simulations of the colliding pulse injection of electrons in plasma wakefields

In this paper, we report on recent experimental results on electron acceleration using two counterpropagating ultrashort and ultraintense laser pulses. We demonstrate that the use of a second laser pulse provides enhanced control over the injection and subsequent acceleration of electrons into plasma wakefields. The experimental results show that the electron beams obtained in this manner are collimated, monoenergetic, tuneable, and stable. Simulations of the process emphasize the crucial role of kinetic effects and the need for self-consistent models.