Numerical simulations of early-stage dynamics of electron bunches emitted from plasmonic photocathodes

Abstract

High-brightness electron sources are a key ingredient to the development of compact accelerator-based light sources. The electron sources are commonly based on (linear) photoemission process where a laser pulse with proper wavelength impinges on the surface of a metallic or semiconductor photocathode. Very recently, the use of plasmonic cathodes – cathodes with a nano-patterned surface – have demonstrated great enhancement in quantum efficiencies (Li et al., 2013 [1]). Alternatively, this type of photocathodes could support the formation of structured beams composed of transversely-separated beamlets. In this paper we discuss numerical simulations of the early-stage beam dynamics of the emission process from plasmonic cathodes carried out using the Warp (Friedman et al., 2014 [2]) framework. The model is used to investigate the properties of beams emitted from these photocathode and subsequently combined with particle-in-cell simulations to explore the imaging of cathode pattern after acceleration in a radiofrequency gun.