Calculation of the parameters of the X-ray diffraction station with adaptive segmented optics on the side beam from the wiggler of the Sibir’-2 storage ring

The mounting of an X-ray diffraction station on the side beam of a 19-pole superconducting wiggler makes it possible not only to use the central synchrotron radiation beam with a wavelength of 0.5 ?, but also to solve problems requiring softer X rays at a synchrotron radiation (SR) intensity exceeding that for the beams from the bending magnet. A numerical simulation of the formation of photon beams from a source and their transmission through the elements of the station (and through the station as a whole) allows one to calculate the parameters of the station, compare it with the existing analogs, determine its potential and actual efficiency of its elements, and estimate the adjustment quality. A numerical simulation of the SR source on the side beam from the wiggler and the focusing channel (segmented condenser mirror, monochromator with sagittal focusing by the segmented second crystal, and segmented focusing mirror) has been performed. The sizes of the focus and the divergence of rays in it are determined with allowance for the finite sizes of segments. The intensity of radiation with a wavelength ?? = 1.0 ? in the focus is determined taking into account the loss in the SR extraction channel and in the focusing channel. The values of the critical wavelength for the side beam from the wiggler and the wavelength resolution are calculated. The intensities in the X-ray diffraction pattern and its angular resolution are found.     

Beam focusing on stations with a Sibir’-2 synchrotron source for single-crystal studies of atomic structures

A scheme for obtaining a stationary monochromatic beam that can be focused in the horizontal and the vertical planes and rapidly tuned to a desirable wavelength with the aid of a bending magnet on a Sibir’-2 synchrotron source has been designed. The channel parameters and the size and profile of a sagittally bent single crystal of the double-crystal monochromator were chosen with the use of numerical simulation.     

Spectrometer of Synchrotron Radiation Based on Diffraction Focusing a Divergent Beam Formed by a Compound Refractive Lens

The results of the first experimental realization of a spectrometer based on the effect of diffraction focusing of X rays by a flat single crystal are discussed. A secondary X-ray source with a relatively high angular divergence and small sizes was formed at the focus of a compound refractive lens having 50 beryllium biconcave elements with a curvature radius of 50 μm. The silicon spectrometer crystal was cut in the form of a wedge of variable thickness, oriented perpendicular to the diffraction plane. The reflection 111 was used for energies of 8.3 and 12 keV. To simulate the experiment, a computer program was developed, which takes into account accurately and for the first time the focusing of radiation by the lens and its subsequent diffraction in the crystal. A calculated curve for a monochromatic beam has made it possible to determine the monochromator spectrum with high resolution from experimental data for a polychromatic beam. It is shown that monochromator resolution increases with an increase in the distance from the compound refractive lens to the crystal.     

Station for X-ray structural analysis of materials and single crystals (including nanocrystals) on a synchrotron radiation beam from the wiggler at the Siberia-2 storage ring

The design of the station for structural analysis of polycrystalline materials and single crystals (including nanoobjects and macromolecular crystals) on a synchrotron radiation beam from the superconducting wiggler of the Siberia-2 storage ring is described. The wiggler is constructed at the Budker Institute of Nuclear Physics of the Siberian Division of the Russian Academy of Sciences. The X-ray optical scheme of the station involves a (1, ?1) double-crystal monochromator with a fixed position of the monochromatic beam and a sagittal bending of the second crystal, segmented mirrors bent by piezoelectric motors, and a (2θ, ω, φ) three-circle goniometer with a fixed tilt angle. Almost all devices of the station are designed and fabricated at the Shubnikov Institute of Crystallography of the Russian Academy of Sciences. The Bruker APEX11 two-dimensional CCD detector will serve as a detector in the station.     

Synthesis of high-quality CdSiP2 polycrystalline materials directly from the constituent elements

High-purity, single-phase CdSiP₂ polycrystalline materials were synthesized directly from the constituent elements by a new method without graphite boat sealed in silica ampoule. The problem of explosions was solved by careful control of the heating and cooling cycle and adopting the two-zone rocking furnace with specially designed temperature profile. Mechanical and temperature oscillations as well as gradient cooling were introduced in the synthesis process. The mechanism and advantages of this new method are discussed. X-ray diffraction (XRD) analysis and Energy dispersive X-ray (EDX) microanalysis both indicated that the synthesized compound is high-quality CdSiP₂ polycrystalline material.     

Technological properties of CSK-1 crystallizer for material research in space

The crystallizer CSK-1 is based on a tubular furnace with five heating elements. The crystallizer operates in an automatic mode, i.e., the setting up of the temperature fields, setting of the sample position in the tube and of the rate and direction of their movement are controlled by a microprocessor running according to a program stored on a magnetic tape. The crystallizer is placed on the Soviet Orbital Laboratory “MIR”. Basic technological properties of the crystallizer were studied by means of an standard probe connected with a computer and of the special ARP device, respectively. The topic of the study was especially the creation of various types of axial temperature fields and of various temperature gradients, the rate of heating and spontaneous cooling of the furnace, the temperature stability, and so on.     

Side Entry Specimen Stages

The basic concepts involved in the design of side entry specimen devices for performing in-situ experiments are discussed. Examples of several working specimen stage designs are shown in which common experimental variables such as tilting, heating, cooling, straining and atmosphere control are used in various combinations.     

Global heat loss and thermal stress analysis in Czochralski crystal growth

Based on our invention of an energy‐efficient Czochalski crystal growth furnace, a 2D‐axisymmetric numerical simulation model of LiNbO₃ crystal growth is developed. The heat transfer, melt and gas flow, radiation and the interface deflection have been examined. Heat losses in the furnace and the insulator, as well as the heating power and thermal stress distribution at three stages of crystal growth are calculated in detail. It is found that a large proportion of heat dissipates through the water‐cooling system, and at the steel shell of the furnace, gas convection heat transfer is the major cooling mechanism. Less heat dissipation by radiation and more heat flux by gas convection to the crystal sidewall results in a larger concentrated thermal stress, which may induce large crystal cracks in the growth process. The simulation results of heating power are in coincidence with the actual power of our furnace, which verifies the feasibility of our model. The detailed information with respect to the device obtained from simulation can help to optimize the energy‐saving design and growth process.     

The belok station for protein crystallography on the synchrotron radiation beam from the bending magnet in the Sibir-2 storage ring

Design modifications made in the initial project of the Belok station in the Sibir-2 storage ring and the alignment and calibration methods are considered. The main operating parameters of the station are reported. Protein single crystals in a capillary at T = 293 K and without a capillary at T = 95 K, powders (angular resolution Δ2? = 0.04°), and nanocrystalline Na and Cl₂ precipitates (sizes, shape, and orientation) in electron-irradiated NaCl crystals have been investigated. The problem of focusing of a short-wavelength synchrotron radiation beam with sagittal bending of the second crystal in the double-crystal monochromator at a limited source-to-sample distance is solved in the Belok project.     

Crystal monochromator with a large curvature of the sagittal bending

A new crystal monochromator is designed and tested. The crystal monochromator allows for the use of a large curvature of the sagittal bending and makes it possible to focus synchrotron radiation at a short wavelength and a limited distance from the synchrotron radiation source to the sample.     

Texturtopographie

Using the X-ray beam coming from a Johannsson monochromator the represented method records the diffracted intensity not at the place of focusing according to Guinier technique but in the double distance from the specimen. If the analysed object is e.g. a polycristalline metal sample with inhomogenious texture one can obtain a texture topograph with a relationship between reflectivity of the reflection spot and the blackening of the equivalent spot on the film. A necessary requirement is a soller slit placed between sample and film to eliminate other than the focused rays of the diffraction are.     

Study of a macrodefect in a silicon carbid single crystal by means of X-ray phase contrast

The morphology of a macrodefect in a single-crystal silicon carbide wafer has been investigated by the computer simulation of an experimental X-ray phase-contrast image. A micropipe, i.e., a long cavity with a small (elliptical in the general case) cross section, in a single crystal has been considered as a macrodefect. A far-field image of micropipe has been measured with the aid of synchrotron radiation without a monochromator. The parameters of micropipe elliptical cross section are determined based on one projection in two directions: parallel and perpendicular to the X-ray beam propagation direction, when scanning along the pipe axis. The results demonstrate the efficiency of the phase contrast method supplemented with computer simulation for studying such macrodefects when the defect position in the sample volume is unknown beforehand.     

溶剂热法制备Al掺杂ZnO薄膜的机理研究

采用溶剂热法在玻璃衬底上制备Al掺杂的ZnO薄膜,研究了溶剂热过程中升温、恒温和降温三个阶段分别对薄膜物相和形貌的影响,探讨了薄膜的生长机理.结果表明,升温阶段只是形核过程,基片仅在升温阶段与前驱液接触不能形成薄膜;基片在升温-恒温阶段与前驱液接触可制备(002)择优取向的薄膜;恒温阶段既有成核过程又有晶体生长过程,基片仅在恒温阶段与前驱液接触可以制备薄膜;降温阶段薄膜继续生长.     

On the surface shape of an X-ray monochromator

It is established that the surface of a monochromator for a point X-ray source in diffractometers is the surface of revolution of a circle arc around the straight line connecting the X-ray source and detector. It is shown that scattering occurs at the points of intersection of the monochromator surface with the set of ellipsoids of revolution, in whose focuses the X-ray source and detector are located. A formula is obtained for calculating the misorientation angle of mosaic blocks. The limits of variation in the angle for Fe \(K_{\alpha _1 } \), Cu \(K_{\alpha _1 } \), and Mo \(K_{\alpha _1 } \) radiations are determined. It is shown that there is no unified continuous reflecting monochromator surface, and the true reflecting surface is fractal.     

Growth of Bi-Sr-Ca-Cu-O based superconducting whiskers

Superconducting whiskers of the Bi system have been grown by heating a glassy melt-quenched plate in a stream of O₂ gas. We have examined the growing phase and superconductivity of the whiskers grown at the different heating and cooling conditions. The Bi₂Sr₂CaCu₂O₈ (2212 phase) whiskers are grown from a wide range of initial compositions when the melt-quenched plates are heated at 840°C. The Bi₂Sr₂CuO₆ (2201) phase is dominant in the whiskers grown at lower temperature, 820 and 810°C. The growing pure 2223 whiskers have not been obtained so far. For the superconductivity of the 2212 whiskers, high oxygen partial pressure (P_O2, rapid cooling and higher heating temperature are preferable. Low P_O2 and slow cooling are preferable for the 2223 phase contained in the 2212 whiskers as a minor part. Heating time does not give remarkable effects on the growing phase and superconductivity.     

Dielectric behaviour of TGS crystals poled by doping on repeated temperature cycling

Data characterizing the stability of basic dielectric properties against thermal treatement are presented for crystals of TGS and deuterated TGS doped with alanine or bivalent platinum. Complex permittivity and over-all polarization have been measured during a heating-cooling cycle. In alanine doped crystals the heating and cooling curves are perfectly reproducible. In Pt-doped samples the reproducibility is worse, for pure TGS the properties on cooling are strongly influenced by domain effects. These data made it possible to estimate the change of the figures of merit for pyroelectric ir detectors due to transient heating.     

Continuous cooling crystallization kinetics of a molten blast furnace slag

The crystallization characteristics and kinetics of a molten blast furnace slag during continuous cooling were investigated. Samples of molten blast furnace were continuously cooled both in tiny amounts in a differential scanning calorimetry (DSC) equipment and in bulk states in a cooling mold. The mineragraphy and morphology were investigated by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). The continuous cooling crystallization kinetics were studied using different models based on DSC data. The results show that akermanite (2CaO·MgO·2SiO₂) and gehlenite (2CaO·Al₂O₃·SiO₂) are the major minerals in the continuously cooled crystalline blast furnace slag. The mechanism of crystallization of the blast furnace slag during continuous cooling is dominated by both surface nucleation and one-dimensional growth with bulk nucleation, which is significantly different to that during heating. The activation energy of crystallizations of akermanite and gehlenite was determined by Kissinger and Matusita methods. The values obtained are much higher than that yielded during heating.     

Initial observations of dynamically heated bone

Understanding the chemical changes within bone during heat treatment has become essential within many fields including biomaterials, archaeology and forensic science. All current approaches report the systematic heating and cooling of bone specimens (a ‘static’ approach). These provide information on modifications to mineral structure and chemistry including recrystallisation and thermal decomposition from bone specimens cooled to room temperature. In order to understand these fundamental processes further, we adopted, for the first time, a dynamic heating protocol coupled to an X‐ray diffraction probe, which provides in situ analysis at temperature. This approach allows physico‐chemical processes to be observed at elevated temperatures for five different bone types: bovine, porcine, human, rostrum and red deer antler. The results, when compared to static heating studies, illustrate individually the effects of heating and cooling upon bone mineral. On heating, the onset of recrystallisation occurs rapidly over a short temperature range for all bone types. It is proposed the continued growth of the hydroxyapatite crystals is limited by the mineral to organic ratio. Investigation of the lattice parameters has also indicated significant differences between the bone types, suggesting species differentiation is possible using X‐ray diffraction analysis. Statistical analysis of the ‘a’ axis lattice parameter data revealed human bone is distinguishable from the other bone types.