Abstract: An extended radiating aperture for X-rays is provided by means of a stationary target of an X-ray emissive metal positioned for uniform illumination by high speed electrons emanating from a cathode and accelerating through a difference of potential between the cathode and the target. The target is in the form of a relatively thin film which can be deposited on a substrate transparent to X-radiation. The substrate cools the target. The generator is advantageously utilized with a zone plate which provides a coding on a roentgenogram which is then decoded by an optical processor to form a visible image of an object being X-rayed. An alternative embodiment of the invention includes the use of an inclined transmissive target for enhanced monochromaticity to emitted radiation.