Using large area field emitters (LAFE) as cathodes for RF gun injectors offers significant potential for creating compact, high-power, and high-brightness electron beams, crucial for advanced accelerator technologies. However, when subjected to DC electric fields, LAFEs face significant challenges due to the shielding effect, which limits emission from central emitters and decreases overall current density. Overcoming the shielding effect in an RF gun environment is essential to meet the required beam quality in accelerators. The current distribution of LAFE under DC conditions is influenced by several geometric parameters, such as emitter height, inter-emitter distance, aspect ratio, and the number of emitters. Moreover, in an RF gun setup, LAFEs experience varying macroscopic electric fields at different emitter positions, altering the current distribution compared to DC fields. In this study, we have systematically examined the impact of various LAFE parameters on their field emission performance in an RF gun environment. We have adopted a semi-analytical approach to estimate the current distribution of LAFE, combining analytically calculated field enhancement factors (γ) with numerically calculated applied RF field values. After validating the method with COMSOL simulations, we have applied it to estimate the current distribution of an LAFE cathode integrated into a ½ cell S-band (2856 MHz) gun. The simulation results indicate that, under favorable conditions, a Gaussian spatial beam distribution can be achieved with LAFE, thus mitigating the shielding effect typical in DC fields. By optimizing various LAFE parameters, the desired current and beam distribution patterns can be attained. This study highlights a promising approach for designing LAFE cathodes for RF guns, which could advance accelerator-related technologies.
