Bunching enhancement for coherent harmonic generation by using phase merging effects

Abstract

Abstract In this paper, a promising but simple scheme is investigated to enhance the micro-bunching of the relativistic electron beam for coherent harmonic generation (CHG) by using the phase merging effects. Different from the standard CHG scheme, two special designed dispersion sections (DSs) are adopted with the DS-modulator-DS configuration. The phase space of the e beam is appropriate coupled in DS-I and the electrons within one seed wavelength can merge to the same phase with a matched DS-II. The micro-bunching of the e beam can thus be enhanced by a large margin with much higher harmonic components. Taking the e beams from laser wakefield accelerators (LWFAs) as an example, a start-to-end simulation is performed to show the effectiveness and robustness of the proposed scheme with several configurations. The notable enhancement of the up-conversion efficiency and intense coherent radiation in extreme ultraviolet regime can be obtained within a 3.5-m-long beamline. The proposed scheme offers new opportunities for future compact free electron lasers (FELs) driven by LWFAs and enables prospects for truly compact and widespread system.