Apparatus for X-ray radiography

Claim 1

Apparatus for X-ray radiography, comprising: a first conductive planar electrode adapted to transmit a pattern of differentially-absorbed X-ray radiation, said first electrode having a surface with an array of a plurality of raised portions formed thereon; a second conductive planar electrode spaced from, and parallel to, said first electrode; a sheet of insulative material adjacent the surface of said electrode facing said first electrode; a structured photocathode fabricated as a two-dimensional array of spaced substantially rectangular parallelopiped columns of an x-ray photoemissive material, each of said column being fabricated upon one of said raised portions upon said first electrode surface and being substantially perpendicular thereto, each said column having a substantially constant cross-section and extending from said first electrode surface a portion of the distance to said insulative sheet; said columns defining a grid devoid of said photoemissive material therebetween; an avalanche-amplifying gas filling the gap between the insulative sheet and said array of columns and filling the volume of the grid between said columns; and means for forming an electric field between said first and second electrodes; the photoemissive material of said array of columns emitting, responsive to said X-ray radiation, with charged particles interacting with said gas and said field, respectively, for amplification and subsequent collection at said sheet.