Material characterization based on the interaction of x and gamma radiation with matter is outlined and the need for a high intensity, monochromatic source highlighted. The design and properties of a new, fluorescent x-ray tube are described. This gives a high intensity (5.9 X 109 photons s-1 sr-1 mm-2), quasi- monochromatic output, consisting of the K fluorescent lines of its secondary target, a tantalum cone situated inside the tube. The spectral purity, stability and radiance are reported and comparisons made with radioisotope sources and a conventional tube monochromatized with a curved Ge crystal. In terms of radiance, the `Fluorex' x-ray set compares favorably with the former but not with the latter. However, it offers other advantages over these sources and without being fully optimized already has sufficient monochromatic output to find extensive use for material characterization.
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