M. V. Koval’chuk

Possibilities of Controlling an X-ray Beam with a Crystal Subjected to Long-Wave Ultrasonic Vibrations

X-ray diffraction is experimentally studied in the Laue geometry in a germanium crystal carrying a long-wave ultrasonic wave that creates an alternating lattice deformation along the sample surface. Stroboscopic equipment is used to separate different phases and, correspondingly, different profiles of a spatial deformation distribution from the periodic deformation. A uniform deformation is shown to change the angular position of the X-ray beam, and a nonuniform deformation broadens the angular region of reflection and decreases the peak intensity. Ultrasound can be used to compensate for the static deformation at the place where the single-crystal sample and the resonator are glued together. Apart from the fundamental long-wave harmonic, the crystal contains a parasitic deformation with a shorter wavelength. A simple theoretical model is developed, and it rather accurately describes the experimental results.

Observation of standing x-rays in Bragg diffraction on high-T c superconducting crystals Nd1.85Ce0.15CuO4−δ

Curves of the secondary-fluorescence yield from the constituent elements of high-Tc superconducting crystals Nd1.85Ce0.15CuO4−δ are measured in the dynamic x-ray diffraction regime. The form of the curves attests to the appearance of a standing x-ray wave in the crystal.

X-ray and synchrotron methods in studies of cultural heritage sites

X-ray and synchrotron methods that are most widely used in studies of cultural heritage objects (including archaeological sites)—X-ray diffraction analysis, X-ray spectroscopy, and visualization techniques— have been considered. The reported examples show high efficiency and informativeness of natural science studies when solving most diverse problems of archaeology, history, the study of art, museology, etc.

Evolution of X-ray rocking curves for paratellurite and lithium fluoride crystals under intense ultrasound

Local deformations of the crystal lattice under ultrasonic loading over a wide range of amplitudes have been investigated by means of recording the X-ray rocking curves for paratellurite and lithium fluoride single crystals.

Protein crystallization under microgravity conditions. Analysis of the results of Russian experiments performed on the International Space Station in 2005−2015

Conditions of mass transport to growing crystals have a considerable effect on the crystal size and quality. The reduction of convective transport can help improve the quality of crystals for X-ray crystallography. One approach to minimizing convective transport is crystallization in a microgravity environment, in particular, in space. The data obtained by our research team in protein crystallization experiments on the International Space Station are surveyed and analyzed.

Fast ultrasonic wavelength tuning in X-ray experiment

A method of tuning (scanning) X-ray beam wavelength based on modulation of the lattice parameter of X-ray optical crystal by an ultrasonic standing wave excited in it has been proposed and experimentally implemented. The double-crystal antiparallel scheme of X-ray diffraction, in which an ultrasonic wave is excited in the second crystal, is used in the experiment. The profile of characteristic line kα1 of an X-ray tube with a molybdenum anode is recorded using both the proposed tuning scheme and conventional mechanical rotation of crystal. The results obtained by both techniques are in good agreement.

Development of methods for ultrasonic scanning of X-ray wavelength

The method for X-ray wavelength tuning using an adaptive element (a quartz monolithic resonator modulated by a standing longitudinal low-frequency ultrasonic wave) has been proposed and implemented. This method is characterized by high tuning accuracy and possibility of scanning X-ray beam parameters with a time resolution of up to 3 μs.

Nature of impurities during protein crystallization

Lysozyme crystal growth was studied using reagents of different purity of three trademarks— Seikagaku Corporation (sixfold recrystallized lysozyme), Sigma-Aldrich (threefold recrystallized lysozyme), and Hampton Research (threefold recrystallized lysozyme). Solutions of these reagents were investigated by small-angle X-ray scattering, dynamic light scattering (DLS), ultracentrifugation, and electrophoresis. It was found that crystal-growth and oligomerization processes are more intense in solutions of the reagent of higher purity. The dependences of the fraction of lysozyme oligomers on the supersaturation and purity of the solution are analyzed.

Kossel lines as a new type of X-ray source

The radiation intensity distribution within the Kossel line corresponding to the extremely asymmetric pattern of X-ray diffraction has an anomalous form of a clearly manifested peak exceeding the background intensity by more than two orders of magnitude. A detailed theoretical analysis of this effect is carried out and versions of experimental observation of anomalous Kossel lines are proposed. The possibility of the employment of the effect for obtaining a new source of X rays with a narrow angular collimation is discussed.

Phase Problem in Three-Beam X-ray Diffraction

It is shown that, apart from the purely elastic scattering of X-rays, their inelastic coherent scattering by phonons can play, in some cases, a significant part in the formation of reflection curves for multiple X-ray diffraction. This process may affect the interference pattern for weak reflection, and it must be taken into account when extracting the triplet phase, as was demonstrated by an analysis of the experimental rocking curves obtained for the coplanar three-beam diffraction by a KDP crystal.