Effect of sharp vacuum-plasma boundary on the electron injection and acceleration in a few-cycle laser driven wakefield

The electron injection and acceleration driven by a few-cycle laser with a sharp vacuum-plasma boundary have been investigated through three-dimensional (3D) particle-in-cell simulations. It is found that an isotropic boundary impact injection (BII) first occurs at the vacuum-plasma boundary, and then carrier-envelope-phase (CEP) shift causes the transverse oscillation of the plasma bubble, resulting in a periodic electron self-injection (SI) in the laser polarization direction. It shows that the electron charge of the BII only accounts for a small part of the total charge, and the CEP can effectively tune the quality of the injected electron beam. The dependences of laser intensity and electron density on the total charge and the ratio of BII charge to the total charge are studied. The results are beneficial to electron acceleration and its applications, such as betatron radiation source.