Effects of ion barrier film on image noise in generation III image tube

In the third-generation image tube, the input surface of microchannel plate (MCP) is typically coated with an ultra-thin dielectric film, called the ion barrier film (IBF), to prevent ions generated in MCP during operation from migrating back to the photocathode and damaging the activation layer of photocathode, and prolong the operation lifetime. But IBF will serves as a scattering center for electron signal and reduce the signal-to-noise (SNR) of the image tube. In this paper, we present overviews of the IBF roles in third-generation image tubes, and the results of Monte-Carlo simulation on electron transmission through the Al₂O₃ dielectric film with varying electron energy and film thickness. We also calculated and analyzed the noise factors of Al₂O₃ IBF by Monte-Carlo simulation and the quantum noise model. A method of Temporal Domain Segmentation was proposed for statistical calculation. The results show the noise factor of IBF from quantum noise model is 1.07-1.28 at working voltage of 500-800V, and the one from Monte Carlo Simulation is 1.6-2.6.