Abstract
Direct laser acceleration (DLA) of an electron bunch can be achieved by utilizing the axial field of a well-guided, radially polarized laser pulse in a density-modulated plasma waveguide. However, the ponderomotive force of a TWclass laser pulse excites a plasma wave that can generate a defocusing electrostatic field, which significantly deteriorates the transverse properties of the injected electron witness bunch. [1] To improve the quality of the accelerated witness bunch, an additional leading electron bunch, termed a precursor, is introduced to generate ion-focusing force to effectively confine the trailing witness bunch. We conducted three-dimensional particle-in-cell simulations to investigate the effect of bunch charge, transverse size of the precursor, and the axial separation between the precursor and the witness bunch on the efficacy of DLA. Results indicate that the transverse properties of the witness bunch can be maintained and the overall DLA efficiency can be improved when a favorable ion-focusing force is provided by the precursor. [2].