The nature and topological distribution of optical centers within various regions of hot pressed disks of transparent magnesium aluminates spinel ceramics doped with LiF were studied. In the optical absorption spectra of this type of ceramic, bands were revealed at 4.75 eV and 5.3 eV, which were identified with F + -and F-centers, respectively. Because both bands are formed by anionic vacancies which captured one or two electrons, the topological distribution of anionic vacancies was determined. The band at 5.65 eV was also found which is tentatively identified with complex centers of anionic vacancies that capture fluorine ions and electrons. Using X-ray irradiation the variety of absorption bands of hole centers related to cationic vacancies was established. The spatial distribution of cationic vacancies within the ceramic disk was also determined.
The emergence of powerful sources of ionizing radiation, the needs of nuclear energy, technology and medicine, as well as the need to develop reliable methods of protection against the harmful effects of penetrating radiation stimulated the development of such branches of science as radiation chemistry, radiation biology, radiation medicine. When an organic dye solution is exposed to ionizing radiation, it irreversibly changes color. As a result, the absorbed dose can be determined. The processes of interaction of neutron fluxes with an aqueous solution of an organic dye methyl orange (МО) – C14H14N3О3SNa, containing and not containing 4% boric acid, have been investigated. The work was carried out on a LINAC LUE-300 at NSC KIPT. A set of tungsten plates was used as a neutron-generating target. The electron energy was 15 MeV, the average current was 20 μA. The samples were located behind the lead shield and without it, with and without a moderator. Using the GEANT4 toolkit code for this experiment, neutron fluxes and their energy spectra were calculated at the location of experimental samples without a moderator and with a moderator of different thickness (1-5 cm). An analysis of the experimental results showed that when objects without lead shielding and without a moderator are irradiated, the dye molecules are completely destroyed. In the presence of lead protection, 10% destruction of the dye molecules was observed. When a five-centimeter polyethylene moderator was installed behind the lead shield, the destruction of dye molecules without boric acid on thermal neutrons was practically not observed. When the fluxes of thermal and epithermal neutrons interacted with a dye solution containing 4% boric acid, 30% destruction of dye molecules was observed due to the exothermic reaction 10B (n, α). The research has shown that solutions of organic dyes are a good material for creating detectors for recording fluxes of thermal and epithermal neutrons. Such detectors can be used for radioecological monitoring of the environment, in nuclear power engineering and nuclear medicine, and in the field of neutron capture therapy research in particular.
Elementary convection cells (ECC) are formed in horizontal layers of liquid heated from below, and they are experimentally investigated in this work. Results of experimental studies were adequately described by the theoretical model of ECC. It is shown that the addition of aluminum powder to oil transforms oil to a suspension, such that boundary conditions on the solid wall can be regarded as free because there is a slip through the tape of pure oil. Change in the character of boundary conditions is confirmed by the results of numerical processing of experimental results on formation of convective rings on the layer surface by other authors. Two independent methods for determining the velocity of mass transfer in cells with various diameters are described in the article. For cells with a large diameter (17 mm), the maximum velocity of mass transfer was measured at the upper boundary on a deflection angle of the probe. Measured in this way velocity was equal to V<sub>Oil</sub> ≈ 0.2 mm/sec. For cells with a smaller diameter (2 mm), the velocity of oil on the surface of a cell was measured using an optical method and constituted the value from 3.5 mm/s to 5.2 mm/s.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.