Abstract
The theory of a two-dimensionally focusing double-crystal Bragg spectrometer consisting of two crystals bent cylindrically in mutually perpendicular planes is developed. The spectral resolution of this spectrometer is calculated for asymmetrical geometry of diffraction. The value of the resolution is shown to be affected by the following factors: an asymmetry factor, the crystal bending radius and the x-ray source size. Comparison of the focusing double-crystal spectrometer with focusing single-crystal spectrometers for the Johann, Johann–Hamos, Johannson–Hamos and backscattering geometries is carried out.