Highly collimated electron acceleration by longitudinal laser fields in a hollow channel*

A longitudinal electric field is associated with the transverse profile of a laser pulse. Exploiting this longitudinal laser electric field, a novel mechanism to achieve collimated super-ponderomotive electron acceleration is proposed. To realize efficient acceleration, a tailored hollow-core target is used to suppress diffraction and enhance the longitudinal laser electric field. In addition, this structure eliminates the net restoring force that produces transverse electron oscillations in laser-generated ion channels, allowing for improved collimation of accelerated electrons. We use two-dimensional particle-in-cell simulation to demonstrate how energy is transferred from the laser to the electrons.