A High Intensity, Monochromatic, Spatially Coherent X-Ray Source

Abstract

An x-ray source is described that can have high brilliance, monochromaticity and spatial coherence. This source filters, by successive diffraction, spontaneous x-ray radiation produced by electron impact in a Bonse-Hart monolithic crystal monochromater. A germanium single crystal was grooved to form a monolithic monochromater and subsequently was fitted with a filament. Field emitted electrons from the filament impact on the crystal side walls. Thus, the passive Bonse-Hart monochromater is converted into an active x-ray source. The detailed diffraction geometry within the cavity, in the limit of kinematic diffraction theory, is described and compared to the experimentally observed radiation pattern. Since this radiation source achieves its monochromaticity and spatial coherence by filtering it is highly inefficient. However, the diffraction process is highly efficient when the radiation is in the proper geometric direction to satisfy Bragg's law. Thus, the stationary radiation source can have a high brilliance although the input of electrical energy could be well in excess of a rotating anode x-ray tube.