X-ray image intensifier tubes having the photo-cathode formed directly on the pick-up screen

Claim 2

An x-ray image intensifier tube apparatus including an evacuated envelope structure having an x-ray transparent receiving face portion for passing x-ray images therethrough, an x-ray sensitive fluorescent layer forming a pick-up screen inside of said envelope for receiving the x-ray images and converting same to optical images, a photo-cathode for converting the optical images to electron image patterns, an electrode structure for accelerating the electron image patterns and focusing the electron patterns onto a fluorescent screen to produce an intensified optical image for viewing which corresponds to the xray image, wherein the improvement comprises, said x-ray sensitive fluorescent layer being made of a material selected from the class consisting of activated alkali metal halides, and said photo-cathode being formed as a layer directly on said x-ray sensitive fluorescent layer, whereby the sensitivity of the image intensifier tube is enhanced and wherein said layer of x-ray sensitive pick-up screen material is doped at its interface with said photo-cathode with an increased concentration of p-type dopant to produce a favorable band bending of the energy levels of said photo-cathode material, whereby the quantum efficiency of said photo-cathode is increased.

Claim 3

An x-ray image intensifier tube apparatus including an evacuated envelope structure having an x-ray transparent receiving face portion for passing x-ray images therethrough, an x-ray sensitive fluorescent layer forming a pick-up screen inside of said envelope for receiving the x-ray images and converting same to optical images, a photo-cathode for converting the optical images to electron image patterns, an electrode structure for accelerating the electron image patterns and focusing the electron patterns onto a fluorescent screen to produce an intensified optical image for viewing which corresponds to the x-ray image, wherein the improvement comprises, said x-ray sensitive fluorescent layer being made of a material selected from the class consisting of activated alkali metal halides, and said photo-cathode being formed as a layer directly on said x-ray sensitive fluorescent layer, whereby the sensitivity of the image intensifier tube is enhanced and wherein said layer of x-ray sensitive pick-up screen material is doped at its interface with said photo-cathode layer with an increased concentration of p-type dopant in sufficient quantities to produce an increased blue quantum efficiency typically falling within the range of 20 to 35 percent.

Claim 4

An x-ray image intensifier tube apparatus including an evacuated envelope structure having an x-ray transparent receiving face portion for passing x-ray images therethrough, an x-ray sensitive fluorescent layer forming a pick-up screen inside of said envelope for receiving the x-ray images and converting same to optical images, a photo-cathode for converting the optical images to electron image patterns, an electrode structure for accelerating the electron image patterns and focusing the electron patterns onto a fluorescent screen to produce an intensified optical image for viewing which corresponds to the x-ray image, wherein the improvement comprises, said x-ray sensitive fluorescent layer being made of a material selected from the class consisting of activated alkali metal halides, and said photo-cathode being formed as a layer directly on said x-ray sensitive fluorescent layer, whereby the sensitivity of the image intensifier tube is enhanced and wherein said layer of x-ray sensitive pick-up screen material is doped at its interface with said photo-cathode layer with an increased concentration of p-type dopant in sufficient quantities to produce an increased blue quantum efficiency typically falling within the range of 20 to 35 percent.

Claim 5

The apparatus of claim 2 wherein said pick-up screen layer is activated with an activator material and concEntration of such activator material to cause the optical fluorescence of said pick-up screen to occur principally in the blue spectral range of optical wavelengths at room temperature.

Claim 6

An x-ray image intensifier tube apparatus including an evacuated envelope structure having an x-ray transparent receiving face portion for passing x-ray images therethrough, an x-ray sensitive fluorescent layer forming a pick-up screen inside of said envelope for receiving the x-ray images and converting same to optical images, a photo-cathode for converting the optical images to electron image patterns, an electrode structure for accelerating the electron image patterns and focusing the electron patterns onto a fluorescent screen to produce an intensified optical image for viewing which corresponds to the x-ray image, wherein the improvement comprises, said x-ray sensitive fluorescent layer being made of a material selected from the class consisting of activated alkali metal halides, and said photo-cathode being formed as a layer directly on said x-ray sensitive fluorescent layer, whereby the sensitivity of the image intensifier tube is enhanced and including means for applying an electrical potential across said x-ray pick-up screen layer for causing current in said pick-up screen generated by absorbed x-rays to flow into said photo-cathode layer and there add to the photoemission current, said potential applying means including a first electrode formed by an electrically conductive x-ray transparent receiving face portion of said vacuum envelope contacting one face of said pick-up screen and a second electrode formed by an electrical contact made to said photo-cathode layer for contacting the other face of said pick-up screen.

Claim 7

An x-ray image intensifier tube apparatus including an evacuated envelope structure having an x-ray transparent receiving face portion for passing x-ray images therethrough, an x-ray sensitive fluorescent layer forming a pick-up screen inside of said envelope for receiving the x-ray images and converting same to optical images, a photo-cathode for converting the optical images to electron image patterns, an electrode structure for accelerating the electron image patterns and focusing the electron patterns onto a fluorescent screen to produce an intensified optical image for viewing which corresponds to the x-ray image, wherein the improvement comprises, said x-ray sensitive fluorescent layer being made of a material selected from the class consisting of activated alkali metal halides, and said photo-cathode being formed as a layer directly on said x-ray sensitive fluorescent layer, whereby the sensitivity of the image intensifier tube is enhanced and including means for applying an electrical potential across said x-ray pick-up screen layer for causing current in said pick-up screen generated by absorbed x-rays to flow into said photo-cathode layer and there add to the photoemission current, said potential applying means including a first electrode formed by an electrically conductive x-ray transparent receiving face portion of said vacuum envelope contacting one face of said pick-up screen and a second electrode formed by an electrical contact made to said photo-cathode layer for contacting the other face of said pick-up screen.