Light scattering in glass ceramic x-ray storage phosphors

Abstract

We have performed numerical simulations to determine the modulation transfer function for glass ceramic x-ray imaging plates where the image readout is by a scanned laser beam. We focus, in particular, on the role of the effective scattering length in determining the width of the modulation transfer function, covering a range of scattering lengths describing very opaque to very transparent glass ceramics. We find that the shape of the modulation transfer function is, in general, bimodal, with a broad contribution from the laser beam width, and superimposed a narrow one from scattering. The overall width of the modulation transfer function reaches a minimum when the scattering length is comparable with the beam width, and so scattering lengths either much greater or less than the beam width, corresponding to either strongly scattering or highly transparent glass ceramics, give the best expected spatial resolution. However, for a practical range of scattering parameters, transparent glass ceramics are predicted to have a superior resolution compared to very opaque ones. Simulations are included which also demonstrate the effect of particle size, optical absorption, and readout laser power. Stronger optical absorption at the wavelength of the stimulating beam in comparison with that at the wavelength of the emitted light has a markedly beneficial effect on the spatial resolution at the expense of sensitivity. Simulation results are confronted with experimental results for a commercial BaFBr:Eu2+ powder-based imaging plate and a europium-doped fluorozirconate glass ceramic, and good agreement is obtained.