Transactions of the Korean Nuclear Society Virtual Autumn Meeting December 17 18 The Size Effect of Powdered Scintillator on High Resolution X ray Imaging System
Digital X ray imaging uses a converter which emits visible light (indirect) or electrons (direct) when absorbing X ray. Indirect system uses a scintillator as a converter with light detector [1 4] A scintillator is a substance that emits visible light when it reacts with Xray or other radiations. The structure and optical properties of scintillators affect the quality of X ray images. Powdered scintillator screen for X ray image is used a lot in industry, medical diagnostics and various fields [5 9] In such a scintillator, the optical light generated from the scintillator is optically diffused by other grains, resulting in light spread, which reduces the spatial resolution of X ray image [10 12] However, if nanoparticle scintillators are used for powderedscintillator screen, high spatial resolution can be achieved due to low light spread [13, 14] In this experiment, powdered zinc tungstate (ZnWO4) scintillators were prepared by the solid state reaction. ZnWO4 is of great interest as ultraviolet, X ray, g ray, electron beam and proton beam scintillator [15 19] For the above reasons, ZnWO4 has the unique characteristics about luminescent property, high density, high chemical stability, short decay time, low afterglow, and economical price [16, 20 25] Meanwhile, my research team developed the highresolution X ray inspection system (HRXIS) [26] This system consists of a carbon nano tube (CNT) based miniature x ray tube, a scintillator, an optical lens, and a scientific complementary metal oxide semiconductors (sCMOS) detector. The concept of the developed system is that transmits the X ray in the form of an object attached to a scintillator, and then magnifies the image formed on the scintillator screen using an optical lens, then acquire images on the sCMOS detector. This system not only can acquire X ray images with high spatial resolution, but also inspect the internal defect of micro sized small objects. In this study, the zinc oxide nanoparticles and tungsten oxide nanoparticles used in the solid state reaction were synthesized using anodization method. Anodization method is that if a platinum relative electrode and a metal wire are added to the electrolyte and then a voltage of 10 100 V are applied, oxidation and etching occurs on the metal wire resulting in metal oxide nanoparticles [27] ZnWO4 nanoparticles were fabricated through the solid state reaction using asprepared zinc oxide nanoparticles and tungsten oxide nanoparticles. The solid state reaction was carried out at different temperatures for fabricating the various sizes of ZnWO4 powders. The different sizes of ZnWO4 powders were fabricated as thin screens on silicon glasses. These scintillator screens were applied to the HRXIS for obtaining X ray image. Finally, it was evaluated whether high spatial resolution of X ray images can be obtained when nanoparticle scintillators are applied to high resolution X ray imaging.