Formation and Characterization of Concentration Inhomogeneities in Melt-Grown Crystals

Crystallography Reports - The specific features of the formation of concentration inhomogeneities in crystals grown by the Czochralski method (GaSb:Te, Ge:Ga) and by the Bridgman method...     

Radioactive-Ion Beams for the Fission Study of Heavy Neutron-Rich Nuclei

Physics of Atomic Nuclei - Quasi-elastic, multi-nucleon transfer reactions induced by the radioactive-ion beams with energy 4–6 MeV/u allow one to produce moderately excited neutron-rich...     

Exposure of nuclear track emulsion to 8He nuclei at the ACCULINNA separator

Nuclear track emulsion is exposed to a beam of radioactive ⁸He nuclei with an energy of 60 MeV and enrichment of about 80% at the ACCULINNA separator. Measurements of 278 decays of the ⁸He nuclei stopped in the emulsion allow the potential of the α spectrometry to be estimated and the thermal drift of ⁸He atoms in matter to be observed for the first time.     

Effect of properties of superheavy nuclei on their production and decay

Properties and stability of superheavy nuclei resulting from hot fusion are discussed. It is shown that the microscopic–macroscopic approach allows obtaining the closed proton shell at Z ≥ 120. Isotopic trends of K-isomeric states in superheavy nuclei are predicted. Evaporation residue cross sections in hot fusion reactions are calculated using the predicted properties of superheavy nuclei. Interruption of α decay chains by spontaneous fission is analyzed. Alpha decay chains through isomeric states are considered. Internal level densities in superheavy nuclei are microscopically calculated.     

X-ray diffraction diagnostics methods as applied to highly doped semiconductor single crystals

Si(As, P, B) and GaSb(Si) single crystals are used as examples to demonstrate the possibilities of methods of X-ray diffraction for the diagnostics (examination of a real structure) of highly doped semiconductor crystals. Prominence is given to characterizing the state of impurity: whether it is in a solid solution or at a certain stage of its decomposition. An optimum combination of X-ray diffraction methods is found to obtain the most complete information on the microsegregation and structural heterogeneity in crystals with low and high X-ray absorption. This combination is based on X-ray diffraction topography and X-ray diffractometry methods having an increased sensitivity to lattice strains.     

Mathematical modeling and experimental investigation of the effect of temperature gradients on crystallization processes under terrestrial and space conditions

Mathematical modeling of the processes of heat and mass transfer during directed crystallization under terrestrial and space conditions is performed on the basis of experimental data on the temperature distribution (boundary conditions). Convective processes are described by the system of Oberbeck-Boussinesq equations together with the heat-conduction equation (the Stefan problem). A dependence of the intensity of thermal gravitational convection on the radial and axial temperature gradients is established. It is shown that one of the necessary conditions for the growth of homogeneous semiconductor crystals under both terrestrial and zero-gravity (on board spacecraft) conditions is the absence of the free surface of a melt (the Marangoni convection) and optimization of the temperature gradients (first of all, the radial gradient).     

Implementation of Temperature-Controlled Method of Protein Crystallization in Microgravity

An experimental scientific equipment for implementing temperature-controlled protein crystallization in capillaries under microgravity has been developed, fabricated, and tested. This crystallization method, providing on-line separate control of crystal growth both in the stage of nucleation of crystals and during their further growth, requires small amounts of protein solution. The equipment has been tested on board of Foton-M4 spacecraft (growth of lysozyme protein crystals of high structural quality in microgravity) using a cyclogram developed in ground-based experiments. The results obtained have demonstrated efficiency and importance of the developed equipment and method for growing biomacromolecular crystals of high-structural quality.

     

X-ray topography study of microsegregation in crystals

Concentration microinhomogeneities in crystals were characterized using x-ray topography, digital image processing, and spectral analysis of signals. Based on the features in lattice strains in such layered inhomogeneous crystals, methods for optimizing the conditions of x-ray topography detection of growth striations were proposed to obtain quantitative information on the composition fluctuation amplitude and spatial characteristics.     

Lysozyme crystallization in a precision-controlled temperature gradient

The possibility to control the crystallization process of biomaterials by the temperature was examined by the mathematical simulation of lysozyme crystallization. The precision-temperature control with creation of a local temperature gradient in solution was demonstrated to allow the growth of lysozyme crystals with high structural perfection.     

Research program for the radioactive beams of the ACCULINNA-2 separator

The ACCULINNA-2 separator is intended to provide beams of exotic nuclei with Z = 1?30, energies of 10?C50 MeV/amu, and intensities that allow one to study excitation spectra and decay dynamics of neutron- and proton-drip nuclei. Examples from studies of the ¹⁰He and ⁶Be nuclei are presented.