Том 82, № 10 (2018)

Experimental data on the angular distributions of ²³²Th, ²³³U, ²³⁵U, ²³⁸U, ^natPb, and ²⁰⁹Bi fission fragments in reactions induced by neutrons with intermediate energies of up to 200 MeV are presented. Measurements are made using the GNEIS time-of-flight (TOF) spectrometer with the neutron source based on the 1-GeV proton synchrocyclotron of the Petersburg Nuclear Physics Institute. Angular distributions and the anisotropy of fission fragments W(0°)/W(90°) calculated from these distributions are given together with the results of other authors. The disagreement between the results obtained in different works is discussed. The data presented in this work for the anisotropy of ^natPb and ²⁰⁹Bi fission fragments in reactions induced by neutrons with energies ranging from the fission threshold to 200 MeV are obtained for the first time.

Observations of collective effects in (A + A) collisions of heavy nuclei confirm the formation of quark–gluon plasma. The systematic study of collective effects of hot nuclear matter associated with the quark–gluon medium and their separation from the effects of cold nuclear matter associated with nucleon medium is one of the main aims of modern high-energy physics. Such studies are conducted using different systems of colliding nuclei. The results are presented from measuring the nuclear modification factors of neutral pions in Cu + Au, p + Au, d + Au, and ³He + Au collisions at 200 GeV.

Studying the properties of strongly interacting quark–gluon plasma (sQGP) is one of the main aims of modern physics. Measuring the invariant yields of neutral pions is one of the best tools for sQGP research, since they can be measured in a wide range of transverse momenta with relatively small statistical and systematic errors. Analysis of specific features of meson production in U + U collisions should help to establish additional constraints on the parameters of theoretical models, and to measure the properties of sQGP more accurately. This work presents the invariant differential transverse-momentum spectra and nuclear modification factors of neutral pions produced in U + U collisions of four different classes of centrality at an energy of 192 GeV.

A simple algebraic model with rules of isospin superselection is formulated and tested on few-nucleon systems. It is shown that physically obtainable states corresponding to the bound states of these nucleons can be gained by applying symmetrical monoidal C* categories whose objects are G-modules, and whose morphisms are G-invariant homomorphisms.

The two-stage two-proton virtual nuclear decay theory and superfluid atomic nucleus model are used to investigate the total and partial widths, and the angular distributions of the emitted protons, for the two-proton diagonal virtual decay of the ground state of the \({}^{{19}}{\text{Mg}}\) nucleus into the ground state of the ¹⁷Ne nucleus. It is shown there is a set of parameters of the proton shell potential and superfluid proton–proton interaction for which the calculated total width of the two-proton decay of the \({}^{{19}}{\text{Mg}}\) nucleus agrees with its experimental value.

Results are presented from investigating deviations of the coefficients of P-odd asymmetries in the angular distributions of fragments produced by the low-energy fissioning of actinide nuclei by polarized neutrons, calculated using the quantum fission theory with allowance for wriggling vibrations, from the coefficients of these asymmetries described by Bohr’s formula. By comparing relative errors of the experimental measurements of Р-odd asymmetry coefficients and deviations of the theoretical values of asymmetry coefficients, calculated with allowance for the wriggling vibrations of a fissile nucleus, from their values obtained using Bohr’s formula, estimates of wriggling vibration parameters \({{C}_{{\text{w}}}} \leqslant 30\) and \({{C}_{{\text{w}}}} \leqslant 15\) are determined for ²³³U and ²³⁵U nuclei, respectively, for which deviations from Bohr’s formula can be detected.

A new formalism that combines the simplicity of the mathematical apparatus of the Poisson distribution and a correct description of the decay of the last nucleus of a system in a binomial distribution is proposed, based on Poisson and binomial distributions. The mathematical apparatus of the model for the creation and death of particles in a sub-Poisson distribution is presented, along with the results from comparing descriptions of the radioactive decay of nuclei using Poisson, binomial, and sub-Poisson distributions for a medium based on uranium-235.

The ^110mAg isomer is examined as a new object for studying the triggered de-excitation of nuclear isomers in pulsed laser plasma. The main advantages of ^110mAg are the low energy (1128 eV) of its transition to the trigger level (leading to the de-excitation of ^110mAg), which is comparable to the electron temperature of plasma, and the long lifetime of the trigger level (36 ns), which allows one to separate plasma interferences in detecting of ^110mAg de-excitation.

The geometry and material content of the Yalina-Booster two-zone subcritical assembly driven by external neutron sources are described, along with the instrumentation and conditions of experimental measurements. ²⁵²Cf isotope and a neutron generator with a TiT or TiD neutron-producing target are used as external neutron sources. The results are presented from analytical and experimental estimates of the levels of subcriticality in two core configurations: (1) with a fueled core (uranium dioxide of 10% enrichment in the thermal zone and uranium dioxide of 21% enrichment in the fast zone) and (2) with uranium dioxide of 10% enrichment in the thermal zone and without fuel in the fast zone. The calculated effective fractions of delayed neutrons in the considered thermal zone are compared. It is shown that the main kinetic parameters are defined by the thermal zone. The calculated results are compared to experimental ones, and the discrepancies are analyzed.

The dynamics of the structural and phase composition of Fe₃O₄ nanoparticles in different media is established. The dependence of the change in the degree of degradation on the acidity and the time of residence in a medium is established. X-ray diffraction and energy dispersive analyzes show there is a sharp increase in the concentration of defects in the crystal structure in acidic media, due to the presence of amorphous regions caused by the emergence of hydroxide compounds. It is established that using gold for the coating of Fe₃O₄ nanoparticles protects nanoparticles from degradation and amorphization. Knowledge of the rate and degree of degradation of nanoparticles allows clarification of the time frame for the applicability of nanoparticles with potential applications in biomedicine.

A prism mass spectrometer with triple focusing of the ion beam using a cone-shaped achromatic prism (CSAP) is considered. The CSAP has a record high angular mass dispersion of approximately 50 rad upon 100% variation of the mass. The performance of a prism mass analyzer with collimating and focusing transaxial lenses is simulated using the Monte Carlo method. The resolution and the quality parameters of such a mass analyzer are shown to exceed those of existing static devices by several times. A resolving power of several million can be obtained using narrow beams on a small device with sub-meter dimensions.