Physical Properties of Calcium Tungstate X-Ray Screens

Abstract

The absolute energy of the light from a fluorescent calcium tungstate x-ray screen, its spectral distribution, and the efficiency of conversion from x-rays to light have been determined. The absolute energy and its spectral distribution were obtained spectrographically by comparison with a standard tungsten filament lamp. Equations are given for determining the distribution of light in the diffusing screen material, and calculation of the light losses are made for varying screen thickness and x-ray absorption. The data for energy distribution of the ingoing x-rays were taken from measurements obtained in this laboratory by a new method to be published elsewhere. Allowance for scattering and secondary x-radiation was made and a conversion efficiency of 5.0 percent was obtained for this calcium tungstate phosphor.