A method for implementing the diffraction of a widely divergent X-ray beam
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RACTION AND SCATTERING OF IONIZING RADIATIONS
A Method for Implementing the Diffraction of a Widely Divergent X-Ray Beam K. T. Avetyan and M. M. Arakelyan Yerevan State University, ul. A. Manukyana 1, Yerevan, 375025 Armenia e-mail: [email protected]; [email protected] Received November 21, 2007
Abstract—A method for implementing the diffraction of a widely divergent characteristic X-ray beam from a standard X-ray tube with a linear focal spot was improved. X rays, passing through a diaphragm 30 µm in diameter, diffract from a crystal adjacent to the diaphragm. The crystal, together with a photographic plate, rotates around the axis perpendicular to the plate. It is shown that the diffraction image is a set of hyperbolas in this case. The equations of the hyperbolas are obtained and investigated. A method for interpreting the diffraction images in the case of small crystal asymmetry is proposed. PACS numbers: 78.70.Ck, 61.10.-i, 61.10.Eq, 61.10.Nz DOI: 10.1134/S1063774508060059
A characteristic feature of the diffraction of a widely divergent characteristic X-ray beam is that a large number of Bragg reflections (sometimes more than 20) can be simultaneously detected in the form of conical cross sections by a plane of a photographic plate. X-ray diffraction images obtained by different methods based on the use of widely divergent beams contain a large amount of data on the crystal structure of the object under study; therefore, such methods are widespread. In particular, the geometric features of the methods for interpreting diffraction images and possibilities of these methods were considered in detail in [1–4]. Experiments were performed on a microfocus generator with a capillary tube of the shoot-through type, in which the anode was a ~20-µm-thick metal foil at the capillary face. The anode spot, about 10 µm in size, was formed on the inner surface of the window. The experimental setup and the first test diffraction images obtained from the local regions of a crystal by the method of a widely divergent beam in reflection geometry were described in [5–7]. The results of precise measurements of the lattice parameters of a dislocation-free diamond crystal were reported in [8]. The source of a divergent X-ray beam was a thin (~2 µm) copper foil, whose rear side was irradiated with a focused electron beam formed in a scanning electron microscope. High measurement accuracy was obtained due to the small size of the focal spot and large camera sizes (~700 mm). The measurements were carried out in transmission geometry at µt > 1, with an allowance for multiwave scattering. In [9], the crystal structures of polycrystalline Al and BaTiO3 samples were investigated. It was shown that the above-mentioned method makes it possible to find a correlation between boundaries of neighboring grains. A capillary tube of the
shoot-through type was used as a source of a divergent radiation beam (the anode was a thin iron foil and the anode voltage ranged from 30 to 40 kV). Anisotropy was revealed in nanostructures in the grazin
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