441spectrometer with a single dispersing crystal with la, =O (i.e. a 'perfect' crystal) and a source of very small dimension in the plane of diffraction then a 'film' profile with s = 0 has twice the angular dispersion of the 'counter' profile (see Fig. 1 b). This suggests the possibility of increasing the numerical dispersion of the 'film' profile by using a non-standard 'inverse' scan mode with s=-l,-2, etc. to increase the effective dispersion relative to the 'counter' profile by 3, 4, etc. AbstractA general formula is obtained for the intensity distribution in the film behind a single crystal in the case of spherical-wave X-ray multiple diffraction. The theory takes into account the phase shift of the waves not only inside the crystal but also in the vacuum before and after the crystal along the wave path source-crystal-film of length L. The topographic images are calculated in the case of (220/242/044/244/202) six-beam diffraction of Cu Ka radiation in a germanium crystal of thickness 0.2 mm for different values of L The enhancement of the anomalous transmission effect is weakly displayed on the topographs because of strong scattering of the radiation inside the crystal. The intensity distribution depends on L. The possibility is shown of focusing X-rays to a considerable extent.
Results of an experimental and theoretical analysis are presented, concerning the six‐beam (220/242/044/―224/―202) diffraction of X‐rays in thick perfect Ge crystals, under the conditions when a part of the diffracted beams is Bragg reflected. Three cases are considered, when one, three, or all five diffracted beams are Bragg reflected. It is shown theoretically that an enhancement of anomalous transmission for the Laue beams takes place in all these cases. Experimentally this effect is observed in the third case on the incident beam topogram, when the two‐beam Borrmann effect corresponds to Bragg reflection and is more weakly revealed than in the Laue case. Experimentally as well as theoretically an unusual behaviour of the integral intensity for the (044) beam is observed, when the number of Bragg beams varied from one to five.
An X-ray one-dimensionally focusing system, a refracting-diffracting lens (RDL), composed of Bragg double-asymmetric-reflecting two-crystal plane parallel plates and a double-concave cylindrical parabolic lens placed in the gap between the plates is described. It is shown that the focal length of the RDL is equal to the focal distance of the separate lens multiplied by the square of the asymmetry factor. One can obtain RDLs with different focal lengths for certain applications. Using the point-source function of dynamic diffraction, as well as the Green function in a vacuum with parabolic approximation, an expression for the double-diffracted beam amplitude for an arbitrary incident wave is presented. Focusing of the plane incident wave and imaging of a point source are studied. The cases of non-absorptive and absorptive lenses are discussed. The intensity distribution in the focusing plane and on the focusing line, and its dependence on wavelength, deviation from the Bragg angle and magnification is studied. Geometrical optical considerations are also given. RDLs can be applied to focus radiation from both laboratory and synchrotron X-ray sources, for X-ray imaging of objects, and for obtaining high-intensity beams. RDLs can also be applied in X-ray astronomy.
An X-Ray Resonator for Silicon single crystal (440, 404) configuration's NiK 2-radiation is offered and principally carried out. Asymmetric reflections (where reflecting planes consist 30 0 angle with block planes) were used. In contrast to [1], the incident beam enters the resonator and undergoes a closed cycle only through Bragg's reflections. The devise was moving by a scanning mechanism perpendicular to the incident beam, and it made possible to take out of the resonator the beams reflected 1,2,3 …times and detect them (Fig. 1). It is obvious that there exists a position in which the beam stays in the resonator, providing a closed cycle (Fig. 2). The devise will give its best results in the case of synchrotron radiation, for in this case it is possible to choose a precise wavelength
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