Software for Modeling and Design of Robust GaAs Photocathodes

The successful operation of the Department of Energy (DOE) X-ray light sources, free electron laser (FEL), and linear accelerator facilities depends on providing reliable photocathodes for generation of low emittance, high-brightness electron beams using conventional lasers. Experiments on GaAs-based photocathodes have demonstrated the potential to generate high-brightness, unpolarized and polarized, electron beams with low emittance. However, high-fidelity simulation capabilities are needed to design and engineer robust GaAs photocathodes that meet or exceed the desired operational parameters for the DOE facilities. Three dimensional, particle-in-cell (PIC) codes can accurately simulate the evolution of electron beams in accelerator cavities but lack algorithms for modeling the physics of electron emission from photocathodes. We will develop and implement software code for modeling electron emission from GaAs photocathodes within the VORPAL Computational Framework to enable simulations of the complete electron generation process including creation of electron-hole pairs due to photon absorption, transport of charge carriers, and emission from negative electron affinity surfaces.Commercial Applications and Other Benefits: The proposed code for high-fidelity simulations of GaAs photocathodes will directly benefit DOE scientists designing electron sources for its user facilities. The new simulation capabilities will also allow the existing PIC code VORPAL (already commercially distributed) to increase its potential for generating further commercial revenue when used in the industry to design semiconductor devices.