Abstract: Radiogra phic screens of reduced quantum noise are prepared from spherical aggregates of randomly oriented plate shaped or needle shaped phosphor particles. These spherical aggregates are produced by spray drying a slurry of the phosphor particles dispersed in a liquid medium in which is dissolved a suitable binder.

Abstract: X-ray image converters using rare earth oxyhalide phosphors activated with terbium and/or thulium ion are described exhibiting improved brightness. Novel reflector means are provided in said x-ray image converter devices which reflect UV radiation incident thereupon back through the phosphor layer to associated readout or recording means sensitive to this wavelength radiation. A multi layer x-ray screen construction utilizing said improved reflector means is also described providing improved image sharpness while further reducing the crossover problem because more reflected UV radiation is being transmitted to an associated photographic film.

Abstract: Rare earth oxyhalide phosphors activated with thulium ion and further incorporating lutetium ion are described exhibiting improved optical resolution for the light image produced therefrom in X-ray image converter devices by reason of the particle size and shape of the phosphor crystals. A multilayer X-ray screen construction utilizing said phosphor material is also described exhibiting improved image sharpness attributable to said phosphor improvement. A preparation method is disclosed wherein the selected oxyhalide is recrystallized in a particular manner to produce phosphor crystals having a more polyhedral shape.

Abstract: Rare earth oxyhalide phosphors activated with thulium ion and further incorporating yttrium ion are described exhibiting improved optical resolution for the light image produced therefrom in x-ray image converter devices by reason of the particle size and shape of the phosphor crystals. A multilayer x-ray screen construction utilizing said phosphor material is also described exhibiting improved image sharpness attributable to said phosphor improvement. A preparation method is disclosed wherein the selected oxyhalide is recrystallized in a particular manner to produce phosphor crystals having a more polyhedral shape.

Abstract: An improved X-ray image converter is disclosed which utilizes a phosphor layer of plate-like rare earth oxyhalide phosphor crystals having said phosphor crystals physically aligned to improve light emission from the phosphor layer. More particularly, said phosphor layer is formed with the plate-like crystals being aligned generally parallel to the longitudinal axis of said phosphor layer at both surface regions while the intermediate phosphor crystals are aligned generally perpendicular to said longitudinal axis. Said improvement can be provided during formation of phosphor layer from a liquid suspension by introducing particular velocity gradients in the flow pattern of said liquid suspension.

Abstract: Rare earth oxyhalide phosphors activated with thulium ion and further incorporating scandium ion are described exhibiting improved optical resolution for the light image produced therefrom in X-ray image converter devices by reason of the particle size and shape of the phosphor crystals. A multilayer X-ray screen construction utilizing said phosphor material is also described exhibiting improved image sharpness attributable to said phosphor improvement. A preparation method is disclosed wherein the selected oxyhalide is recrystallized in a particular manner to produce phosphor crystals having a more polyhedral shape.

Abstract: Oxyhalides of lanthanum and gadolinium and coactivated with thulium ion and further containing an impurity ion and a second coactivator selected from praseodymium and neodymium, including mixtures thereof, exhibit reduced quantum noise when employed in X-ray image converter devices. In the preferred embodiments, small but effective amounts of ytterbium ion can also be incorporated into the phosphor material to reduce afterglow and a multilayer X-ray screen construction is disclosed employing the improved phosphors.

Abstract: An improved X-ray image converter is disclosed which utilizes a phosphor layer of plate-like rare earth oxyhalide phosphor crystals having said phosphor crystals physically aligned to improve light emission from the phosphor layer. More particularly, said phosphor layer is formed with the plate-like crystals being aligned generally parallel to the longitudinal axis of said phosphor layer at both surface regions while the intermediate phosphor crystals are aligned generally perpendicular to said longitudinal axis. Said improvement can be provided during formation of phosphor layer from a liquid suspension by introducing particular velocity gradients in the flow pattern of said liquid suspension.

Abstract: A photo detection system is described utilizing an x-ray source to produce light emission on one or more phosphor materials being used to mark or tag various objects. More particularly, x-ray excitable phosphors are contained in a suitable medium such as marking ink to produce visible emission when irradiated by said x-ray source so that optical detection means positioned adjacent the x-ray source provide a response when objects marked with said phosphors are subjected to such inspection. In the preferred embodiments, an improved postal detection system is provided wherein the postal stamps are marked with at least one x-ray excitable phosphor and said photo detection system can further include a plurality of detection stations along with multiple optical photo detection means at a single station and even a supplemental source of ultraviolet radiation to excite one or more of said phosphors.

Abstract: Oxyhalides of lanthanum, gadolinium and lutetium coactivated with a first activator selected from bismuth and samarium to provide the color of light emission and a second coactivator which increases the amount of stored energy in a stored radiographic latent image are found to be superior in their conversion efficiency of x-rays to visible light.

Abstract: Rare earth oxyhalide phosphors activated with thulium ion are employed in X-ray intensifying screens having modified ultraviolet emission characteristics which reduce crossover effects without significant reduction in film speed and further increases screen brightness. Relatively low concentration levels of the thulium activator ion have been found to shift the ultraviolet emission of said phosphor when excited by X-rays to lower wavelengths in both the ultraviolet and near-ultraviolet spectral regions.

Abstract: Improved performance of rare earth oxyhalide phosphors in x-ray image intensifying screens may be realized by admixing a small but effective amount of inorganic salts such as MgSO.sub.4 or ZnSO.sub.4 with the phosphor prior to the preparation of the screen. It is believed that H+ and SO.sub.4 =ions are present in a protective surface film surrounding each phosphor particle to help preserve the original emission brightness of the phosphor when exposed to humidity as well as reduce attack by volatile organic components which migrate from an associated photographic film.

Abstract: Improved performance of rare earth oxyhalide phosphors in x-ray image intensifying screens may be realized by admixing a small but effective amount of certain fatty acids and fatty acid derivative with the phosphor prior to the preparation of the screen. Alternately, the phosphor powder can be washed with a liquid dispersion or solution of said additives as an equivalent means of providing improved moisture resistance as well as preserving the original emission brightness of the adhesively bonded material when used in x-ray screens.

Abstract: Rare earth oxyhalide phosphors activated with terbium and/or thulium ion are described exhibiting improved brightness which are particularly useful in x-ray image converter devices by reason of producing less light scattering and absorption as a result of superior crystalline characteristics. A multilayer x-ray screen construction utilizing said phosphor material is also described utilizing said phosphor material which exhibits improved image sharpness and a reduced crossover problem. An improved process for producing said phosphor material is further disclosed wherein the selected oxyhalide is recrystallized in a molten alkali metal halide flux to produce the superior crystalline characteristics.

Abstract: Various rare earth phosphor admixtures are described utilizing thulium-activated oxyhalides of lanthanum and/or gadolinium to provide improved performance in x-ray image converter devices. These phosphor admixtures are used in radiographic screens in combination with either blue sensitive or green sensitive photographic film.

Abstract: Improved performance of rare earth oxyhalide phosphors and X-ray image intensifying screens may be realized by admixing a small but effective amount of particular trivalent antimony compounds with the phosphor prior to screen preparation. If the phosphor powder is washed with an aqueous solution of said additive still further improvements are derived.

Abstract: An x-ray image converter for converting x-rays to visible light after passage through a photographed object in order to produce improved colored radiographs on an associated color photographic film attributable to localized color shift in the photographic film medium. The desired color shift produced by the x-ray image converter is achieved with use of a phosphor material which exhibits differential absorption of the x-radiation in the 35-50 KeV region due to K.sub..alpha. edge effects. In the conversion of x-rays to visible light in the desired manner, the new phosphor combination is useful in x-ray image intensifier tubes, in fluoroscopic screens, in radiographic intensifier screens, and other x-ray image converter devices.

Abstract: Thermoluminescent materials have been found suitable for measuring long term exposures to low level ionizing radiation. Oxyhalides of lanthanum, gadolinium and yttrium, including the oxychlorides and oxybromides are activated with terbium and have been found to be most efficient oxygen dominated phosphors having thermoradiant efficiencies with excitation by low level ionizing radiation. Thermoluminescence response increases when the previous materials have elemental hafnium and zirconium additives. The thermoluminescent oxyhalide of the invention is prepared by forming mixed oxalates of the metal constituents, firing the mixed oxalates in air to form an oxide mixture, blending the oxide mixture with an ammonium halide and firing the resultant mixture to form the oxyhalide.

Abstract: Use of terbium-activated rare earth oxyhalide phosphor material in a high-loaded fluorescent lamp having an operating temperature range of approximately 100.degree. C or greater provides high efficiency emission. The phosphor material can be utilized alone or in combination with other suitable phosphor materials at the elevated operating temperatures to generate white-light composite emission. For white-light emission, the phosphor admixture further includes a narrow band red-emitting phosphor along with a narrow band blue-emitting phosphor in suitable portions.

Abstract: The performance characteristics of (Ba,Sr)F, (Cl,Br) : Eu.sup.+2 phosphors may be improved by combining these phosphors with particular rare earth oxyhalide phosphors. In the preferred embodiments, the latter phosphors have relatively small and well-formed crystalline particles which become interspersed with the larger crystalline particles of the (Ba,Sr)F, (Cl,Br) : Eu.sup.+2 phosphor.