A : The "Rainbow X-Ray" (RXR) experimental station at XLab Frascati of the Frascati's National Laboratories (LNF) INFN is a dedicated station for X-ray fluorescence studies based on the use of polycapillary lenses in a confocal geometry. The flexible RXR layout allows investigating specimens of the dimensions ranging from several millimeters up to half meter and weighting up to several tens of kilograms. Compared to similar existing XRF stations, apart of the possibility for investigating large samples, the main advantage of this equipment is the detection system with two spectrometers optimized to work separately at high and at low X-ray energies. The confocal geometry combined with a 3-axes fine motion system makes possible 3D µXRF elemental tomographic acquisitions (colour tomography). At present this station in operation at high XRF energies is used for cultural heritage and geological applications. We present and discuss here the analytical performances of this experimental station pointing out the advantages in di erent application areas. K : Computerized Tomography (CT) and Computed Radiography (CR); X-ray fluorescence (XRF) systems 1Corresponding author.

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The dynamic theory of coherent X-rays excited by a relativistic electron crossing an artificial periodic stratified structure in Bragg scattering geometryhas been developed for the general case of asymmetric reflection. Expressions describing the spectral-angularcharacteristics of radiation have been derived and investigatedyesБелгородский госуниверсите

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Abstract-The possibility of manifestation of the effects of dynamic diffraction in the coherent X ray radia tion of relativistic electrons in a periodic layered medium is studied theoretically in this paper.