A DOUBLE-CRYSTAL X-RAY MONOCHROMATOR IN ANTIPARALLEL POSITION WITH A SAGITTALLY BENT CRYSTAL

The double-crystal x-ray monochromator (spectrometer) in (+,+) setting is high-resolution equipment. Focusing and a considerable increase of the x-ray monochromatic flux without any lowering of resolution may be reached if one of the crystals is properly bent into conical shape. The parameters of the bending are dependent on the wavelength. This ideal conical bending may be replaced by an easier-realizable cylindrical bending where the virtual source and the focus are located on the axis of the cylinder. In this case the higher monochromatic flux, as compared with the flat crystals, may be reached only for Bragg angles from about 35-degrees to about 60-degrees. The highest flux is for the Bragg angle theta = 45-degrees and its nearest neighborhood.