Development of a Phosphor Screen with Mirror Coating to Improve Optical Properties in Radiography

Phosphor screens have attracted increasing global interest because they can aid the acquisition of high-quality images while simultaneously reducing exposure. However, although increasing the thickness of the phosphor screen increases exposure efficiency due to scattered light, it also leads to a broader light spread, which results in poorer resolution. Hence, in this study, we implemented a reflector using a mirror-coating technique on the surface of a phosphor screen and analyzed its characteristics in terms of luminescence intensity and resolution. We present the fabrication and measurement of the phosphor screen based on a reflector containing Gd2O2S:Tb. The phosphor screen containing the reflector can be fabricated via the screen-printing method and roll-to-roll sputtering method. In particular, when compared to the condition without a reflector, Al and Cu reflectors showed improvements in luminescence intensity of 15.7% and 12.2%, respectively, as well as lower full widths at half maximum of 11.45 and 9.08, respectively. This quantitatively demonstrates that Cu and Al are suitable reflector materials to improve exposure efficiency while maintaining resolution in radiography systems. Moreover, because we did not utilize an optical assembly, which improves the transmission efficiency by matching the different refractive indices of the phosphor screen and photo-detector, we believe that the quantity of photons could be further improved if the reflectors were applied to a commercial product. Thus, future studies using single-layer anti-reflector coating techniques with optical assemblies are warranted.

ADVANCED TECHNOLOGY OF LUMINOPHOR SCREENS FOR SOLID RADIOLUMINESCENT LIGHT SOURCES

The article observes different methods of coating the phosphor screens on the tritiated titanium matrices for creating the solid-state radioluminescent light sources (SRLS). Technology of SRLS is alternative to the existing technology of the gas-filled radioluminescent light sources. The main idea of SRLS is in bonding the working isotope (tritium) in the solid matrix and combining it with the phosphor. The key problem of SRLS is to provide the closest contact between the tritiated carrier matrix and phosphor screen. The basic requirements for the phosphor screens for SRLS would be the strength of fixation on the plate, uniformity and radiological and thermal stability. There have been made a comparison of various techniques of coating and fixing the phosphor screens by their effect on spectral and brightness characteristics of SRLS. The improved sol-gel technique of suspended sedimentation of phosphor screen from the potassium water glass binder solution was developed. The composition of the solution was established experimentally and we get the strong and uniform experimental prototypes of the glass coated phosphor screens of various thickness. The developed technology allows to deposit the strong and uniform phosphor coatings without using any additional dispersing agents. Screen thickness regulates by the amount of phosphor in the suspension. Also the optimal thickness of the phosphor screen, giving the maximum luminescence intensity was determined. The two laboratory prototypes of solid-state radioluminescent light sources were manufactured by coating the phosphor directly on the tritium β-source.