Search

Experimental studies of X-ray diffraction from reflecting atomic planes (111) of X-cut quartz single crystal in Laue geometry influenced by the temperature gradient were carried out. It is shown that by using the temperature gradient it is possible to reflect a hard X- ray beam with photon energy near the 100 keV with high efficiency. It has been experimentally proved that the intensity of the reflected beam can be increased by more than order depending on the value of the temperature gradient.

Based on an analytical expression of electron dynamical diffraction derived recently, the exit wavefunctions of nonperiodic samples have been calculated. The results have shown that the amplitude and phase obtained by the analytical expression were in good agreement with those obtained using the multi-slice method. Besides, the influence of the higher-order Laue zone on the wavefunction for different sample thickness was studied in detail and the results showed that the exit wavefunction is dominated by the zero-order Laue zone. When the sample is very thin, the influence of the higher-order Laue zone should be considered.

Results of experimental measurements of transmitted-beam intensity under conditions of six-beam (220, 242, 044, 24, 02) symmetrical Laue diffraction of synchrotron X-ray plane-wave radiation in a silicon crystal are presented along with a computer simulation. A new experimental arrangement with a six-beam collimator was used for the first time. The enhancement of the anomalous-transmission effect (in 3.3 times for ?t = 12) in comparison with the (220) two-beam diffraction has been observed in a direct way. Experimental results agree with the plane-wave theory taking account of two-dimensional convolution.

A description of a method of obtaining Laue patterns from single crystals in sections of metal ingots and the experimental technique used for determining the orientation of the crystals.

Measurements with a double-crystal spectrometer of the intensities of the X-ray beams transmitted and Laue-reflected through germanium single crystals at room temperature are presented. The 220 germanium reflection is used. The half-width and maximum reflecting power of rocking-curves for 15 wavelengths between 0.497 and 2.290 A and crystal thicknesses between 0.04 and 2.28 mm are given. The rocking-curves calculated according to the dynamical theory of X-ray diffraction are in good agreement with those obtained experimentally.

A dynamic theory is developed for the generation of a second x-ray harmonic in an ideal crystal characterized by a quadratic nonlinearity. New types of phase matching near the Bragg diffraction direction are predicted. Directions are found of one-dimensional phase matching in x-ray frequency doubling in accordance with the Laue and Bragg schemes. Calculations are made of the dependences of the amplitudes of second-harmonic waves on the deviation from the exact Bragg reflection direction and on the thickness of a crystal.