3D Monte Carlo tracking model of the external quantum efficiency and halo for subwavelength-grating NaKSb(Cs) image intensifier

A NaKSb(Cs) image intensifier with subwavelength-grating on the optical window is crucial for enhancing external quantum efficiency (EQE) and reducing halo. This study established a comprehensive 3D Monte Carlo model to simulate the photon and electron transport, photoelectric conversion, and emission processes. The simulation results demonstrate that the optical path of the photons in the photocathode is the primary factor influencing the photoelectric conversion efficiency. Multiple reflections of photons in the gap, including lens, window, photocathode and microchannel plate (MCP), are responsible for the halo formation. In addition, the grating can suppress the change in EQE with the incident angle. The model results for the non-grating and single-layer grating cases deviated by 1.57% and 2.44% for the EQE and by 1.03% and 4.35% for the halo, respectively.