Impacts of optical-coupling properties in indirect-conversion detectors

For the optical model of the phosphor screen, it was regarded as a weak absorbing medium in which scattering is caused by refraction at boundaries between the phosphor grains and organic binders. The Monte Carlo method is an efficient tool to understand the phosphor screen physics and sometimes it can replace the experimental measurements. In this study, we have investigated the optical properties of Gd2O2S:Tb granular phosphor screens for the use in indirect-conversion detectors by using the Monte Carlo method. We considered the effects of the optical coupler and the passivation layer of photodiode on the overall detector performance. For various design parameters of a phosphor screen, we investigated the depth-dependent interactions in terms of the light collection efficiency and the point-spread function (PSF)