Speaker
Description
Abstract X-ray Free Electron Lasers (XFELs), ultrafast electron diffraction (UED) and electron microscopy (UEM) require electron beams with ultra-high brightness to enable the development of key new accelerator and material science applications. Photocathodes with high quantum efficiency (QE) and low intrinsic emittance are needed to achieve higher electron beam brightness. Semiconductor photocathodes can deliver high QE which can further be increased, due to optical interference effects, by engineering thin film materials with specific properties. We investigate how material defects, density of states, optical properties, and thin film effects influence QE and intrinsic emittance from Cs_{3}Sb photocathodes. Material properties needed to calculate QE and intrinsic emittance are obtained from state-of-the-art first-principles calculations and available experimental data. We present results from models we have developed to calculate QE and intrinsic emittance using these material properties as input and also taking into account optical interference effects in thin films. We discuss how material properties and defects influence emission properties together with approaches to increase the brightness of electron beams.
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