Influence of powder particle size and scintillator layer thickness on the performance of Gd2O2S:Tb scintillators for neutron imaging

The neutron-capture cross-section of Gd2O2S:Tb scintillators is considerably higher than that of ZnS/LiF scintillators, which are commonly used in neutron radiography. The characteristics of these powder-type Gd2O2S:Tb scintillators correlate to some material parameters, including scintillator layer thickness and powder size. Three types of Gd2O2S:Tb scintillators with different powder particle sizes were prepared, and the effects of the powder size and scintillator layer thickness on the scintillator characteristics were evaluated using a sensitivity indicator (SI) and a beam purity indicator (BPI). The intensity of scintillation increased as the particle size increased. In addition, the intensity of scintillation detected saturated at a specific thickness for each scintillator particle size. This saturation was considered to be caused by differences in the packing rate of the powder near the substrate and the flight paths of thermal neutrons and internal conversion electrons in the scintillator. Additionally, the image quality worsened with increasing scintillator layer thickness. On the basis of our investigation, we determined the optimum powder particle size and layer thickness of the Gd2O2S:Tb scintillator for neutron imaging.