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We describe parabolic compound refractive lenses for hard x- rays that are genuine imaging devices similar to glass lenses for visible light. They open considerable possibilities in both full field and scanning x-ray microscopy, microanalysis, and coherent scattering. They can operate in a range from about 2 keV to 100 keV, are robust, and withstand the white beam of a third generation undulator source. Using aluminum lenses in full field microscopy a field of view of about 300 micrometer can be imaged with magnifications between 10 and 50 and a resolution of about 300 nm. With beryllium lenses an improvement of the resolution to below 100 nm is expected. For microbeam applications, the synchrotron source is imaged onto the sample in a strongly demagnifying setup. With focal distances between 0.3 m and 2 m, the source can be demagnified by a factor 20 to 200 producing a beam with lateral extensions in the micron and sub-micron range. For aluminum lenses, monochromatic microbeams with fluxes above 1010 ph/s and a gain above 1000 are routinely produced at third generation undulator sources. Compound refractive lenses will allow to produce microbeams at energies up to at least 100 keV, making for example, microfluorescence experiments at the K-edges of heavy elements possible. The modular setup of compound refractive lenses allows to adjust the focal length to ideally match the experimental requirements. Assembling and aligning the lens take about 15 minutes. No order sorting apertures are required and the straight optical path allows to remove the lens to align other components.
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