K. M. Podurets

Analysis of synthetic diamond single crystals by X-ray topography and double-crystal diffractometry

Structural features of diamond single crystals synthesized under high pressure and homoepitaxial films grown by chemical vapor deposition (CVD) have been analyzed by double-crystal X-ray diffractometry and topography. The conditions of a diffraction analysis of diamond crystals using Ge monochromators have been optimized. The main structural defects (dislocations, stacking faults, growth striations, second-phase inclusions, etc.) formed during crystal growth have been revealed. The nitrogen concentration in high-pressure/high-temperature (HPHT) diamond substrates is estimated based on X-ray diffraction data. The formation of dislocation bundles at the film-substrate interface in the epitaxial structures has been revealed by plane-wave topography; these dislocations are likely due to the relaxation of elastic macroscopic stresses caused by the lattice mismatch between the substrate and film. The critical thicknesses of plastic relaxation onset in CVD diamond films are calculated. The experimental techniques for studying the real diamond structure in optimizing crystal-growth technology are proven to be highly efficient.

Investigation of the magnetic phase transitions at high pressure by neutron depolarization

Abstract We propose to use the combination of the polarized neutron facility and the anvil high-pressure cell for investigation of magnetic phase transitions in solids. The magnetic phase transition manifests itself in the rise or loss of neutron depolarization. Neutron depolarization in Fe70Ni30 alloy and MnAs under high pressure was studied. Phase transitions from ferromagnetic state to paramagnetic state and vice versa were detected. Ferromagnetic state of MnAs at pressure of about 80 kbar was observed at room temperature.

Study of the crystal device for deflecting high-energy proton beams using synchrotron radiation diffraction

Currently, bent silicon single crystals are used at large accelerators to extract and collimate proton beams. A device for multiple deflection of a proton beam based on several bent silicon strips operating in the volume reflection mode has recently been developed. In this device, the bending of silicon strips successively located on the surface of a thick plate is implemented due to the internal stress induced by grooves mechanically formed on the crystal surface (Twyman effect). Topography based on angular scanning and synchrotron radiation was applied to measure the bending of individual deflector strips and the crystal as a whole. The measurement results are compared with the data obtained with a proton beam.

Characterization of multi-strip crystal deflector for high energy proton beams by synchrotron radiation topography with angular scanning

Currently, for extraction and collimation of proton beam at the large accelerators bent silicon single crystals are used. Recently the new device for multiple deflection of the proton beam was developed, it consists of several bent strips of silicon in the reflection mode. In the device the successive bending of silicon strips at the surface of a thick plate is achieved due to internal stresses in the material of the crystal due to the Twyman effect as a result of applying mechanical grooves. Method of X-ray topography at synchrotron radiation with angular scanning was applied for measurement of bending of the individual strips of the deflector and the crystal as a whole. The results of the measurement are compared with the results obtained in the proton beam.

Comparison of the data of X-ray microtomography and fluorescence analysis in the study of bone-tissue structure

The possibility of localizing clusters of heavy atoms is substantiated by comparing the data of X-ray microtomography at different wavelengths, scanning electron microscopy, and X-ray fluorescence analysis. The proximal tail vertebrae of Turner’s thick-toed gecko (Chondrodactylus turneri) have been investigated for the first time by both histological and physical methods, including X-ray microtomography at different wavelengths and elemental analysis. This complex methodology of study made it possible to reveal the regions of accumulation of heavy elements in the aforementioned bones of Turner’s thick-toed gecko.

Diagnostics of coated fuel particles by neutron and synchrotron radiography

The nondestructive monitoring of coated fuel particles has been performed using contact neutron radiography and refraction radiography based on synchrotron radiation. It is shown that these methods supplement each other and have a high potential for determining the sizes, densities, and isotopic composition of the particle components.

Neutron diffraction investigation of the atomic and magnetic structures of MnAs at high pressures

The atomic and magnetic structures of the MnAs compound are investigated using neutron diffraction at high pressures up to 38 kbar in the temperature range 15–300 K. It is found that, as the temperature decreases under high pressure, the MnAs compound undergoes a spin-reorientation transition from the ferromagnetic orthorhombic phase to a new phase whose magnetic moment has both the ferromagnetic and antiferromagnetic components. The structural and magnetic parameters of the high-pressure phases of the MnAs compound are determined.

Double-crystal diffractometer study of thermal neutron specular reflection

Abstract A double-crystal diffractometer with perfect crystals is used to study the specular reflection of thermal neutrons. If the mirror surface is placed between the crystals then it is possible to separate the effects of surface reflectivity and surface geometry. The critical angle can be determined with an accuracy of 1″ even if the mirror curvature reaches 1′.

Study of Bronze Statues “John the Baptist” and “Dancing Cupid” from the Collections of the Pushkin State Museum

Bronze statues “John the Baptist” and “Dancing Cupid” from the collections of the Pushkin State Museum of Fine Arts have been investigated at the National Research Centre “Kurchatov Institute.” These statues were previously damaged in fire. Before carrying out restoration, it was necessary to perform their complex study, including identification of statue materials; elemental and phase analysis of contaminations; estimation of the state of surfaces and internal parts; and detection of technological elements, as well as hidden defects, corroded parts, and cracks. To this end, scanning electron microscopy with X-ray microanalysis, synchrotron radiation diffraction, and neutron radiography and tomography have been used.

Refraction Introscopy Imaging at Synchrotron Radiation for Medical Diagnostics

The technique of X‐ray refraction introscopy imaging is reviewed. Experiments on the refraction imaging carried out at the Kurchatov Synchrotron Radiation Source with mammographic phantom, small laboratory animals, and model objects are described. Contrast enhancement compared to conventional imaging is demonstrated.