[en] Measured and calculated angular dependences of components of the polarization tensor of a ¹²C nucleus in the 2⁺ state at 4.44 MeV formed in various reactions involving light particles, as well as ²⁴Mg(2⁺, 1.369 MeV) and ²⁸Si(2⁺, 1.78 MeV) nuclei formed in inelastic alpha-particle scattering, are presented. The experimental tensor polarization in question was reconstructed on the basis of the densitymatrix spin-tensors found previously for these nuclei. The parameters of the quadrupole and hexadecapole orientation of the nuclei under study were obtained. The experimental polarization features were compared with the results of calculations based on the coupled-channel method. Special features of the behavior of tensor polarizations in various reactions were discussed. The similarity of the experimental angular dependences of the components of tensor polarizations in inelastic deuteron and ³He scattering on ¹²C nuclei, as well as in inelastic alpha-particle scattering on ²⁴Mg and ²⁸Si nuclei, was demonstrated.

[en] A project of the center for studying reactor materials and solving problems of materials science is presented which will be equipped with the following neutron instruments: a small-angle Membrana diffractometer, a spin-echo spectrometer, and a time-of-flight spectrometer. It is proposed to irradiate materials in the PIK reactor core and use neutron-scattering tools to analyze the structure and dynamics of these materials and investigate radiative defects in the complete experimental cycle (initial material-irradiation-strength tests, thermal loads, and other effects) using materials science techniques.

[en] The angular dependences of the differential cross sections of the ¹³C(d, p)¹⁴C reaction at the deuteron energy of 15.3MeV are presented according tomeasurements for the cases where the final nucleus is produced in the ground state (0⁺) and in the 1⁻ excited state at 6.094 MeV. The angular distribution of protons corresponding to the sum 0⁺ (6.589 MeV) + 3⁻ (6.728 MeV) + 0⁻ (6.903 MeV) of states of the ¹⁴C nucleus that were not separated experimentally is also obtained. These experimental results are compared with their counterparts calculated by means of the FRESCO code for the mechanisms of neutron stripping and sequential neutron and dineutron transfer. The neutron and dineutron spectroscopic amplitudes are calculated for pure and mixed shell configurations. The best set of optical-potential parameters is determined for the entrance and exit reaction channels. It is shown that the neutron-stripping mechanismpermits describing themeasured angular distributions for all states of the ¹⁴C nucleus that were investigated here.

[en] Experimental angular dependences of cross sections for elastic and inelastic scattering and the result obtained by reconstructing the populations of magnetic sublevels, multipole-moment orientation tensors, and polarization tensors are presented for "2"4Mg (2"+, 1.369 MeV) aligned nuclei produced in inelastic proton scattering at E_p = 7.4 MeV. The experimental results in question are compared with the results of calculations based on the coupled-channel method and on the compound-nucleus model, the 3/2"+ resonance in the "2"5Al compound nucleus being taken into account. The orientation features of "2"4Mg (2"+, 1.369 MeV) nuclei produced in inelastic proton and deuteron scattering on "2"4Mg at E_x ≈ 7.5 MeV per nucleon are found to be generally similar despite a substantial difference in the respective differential cross sections

[en] The angular dependence of the differential cross sections for alpha-particle scattering on ²⁸Si nuclei and double-differential cross sections for the reaction ²⁸Si(α, αγ)²⁸Si at E_α = 30.3 MeV is measured for the case of alpha-particle emission angle between 20^o and 160^o and the excitation of low-lying states of the ²⁸Si nucleus (0⁺, ground state; 2⁺ state at 1.78 MeV; 4⁺ state at 4.62 MeV; 0⁺ state at 4.96 MeV; and 3^- + 4⁺, 6.88 MeV + 6.89 MeV). The spin-tensor components of the density matrix for the 2⁺ state at 1.78 MeV and the 4⁺ state at 4.62 MeV in the ²⁸Si* nucleus are reconstructed in a modelindependent way. Seven rank-6 components are reconstructed for the 3^- state at 6.88 MeV. Orientation features of ²⁸Si* are determined. The experimental data in question are compared with the results of the calculations performed under the assumption of the collective-excitation mechanism and by the coupled-channel method.

[en] At the proton energy of E_p = 7.4 MeV, the double-differential cross sections for the reaction ²⁷Al(p, α₁γ)²⁴Mg were measured for 11 values of the alpha-particle emission angle in the range of θ_α = 30°–160°(lab). All even components of the density-matrix spin-tensors were reconstructed for the oriented ²⁴Mg nucleus in the 2⁺ state at 1.369 MeV, and the polarization features of this nucleus, including the populations of magnetic sublevels of the nucleus for all spin projections, multipole-moment orientation tensors, and the quadrupole and hexadecapole tensor polarizations, were determined. Relevant experimental results were compared with their counterparts calculated for the triton-pickup mechanism within the coupled-channel method and in the statistical limit of the compound-nucleus model.

[en] The double-differential cross sections for the reaction ²⁴Mg(d, dγ_1.369)²⁴Mg at the projectiledeuteron energy of E_d = 15.3 MeV weremeasured for deuteron emission angles in the forward hemisphere. All even spin-tensor components of the density matrix for the 2⁺ state of the ²⁴Mg nucleus at 1.369 MeV were reconstructed, and its orientation properties were determined. These experimental results were compared with the results of calculations based on various versions of the coupled-channel method

[en] The results are presented that were obtained by measuring the differential cross sections for the reaction ¹²C(d,d) ¹²C occurring at E_d = 15.3 MeV and leading to the production of a ¹²C nucleus in the ground and the first excited state. The energy dependences of the differential reaction cross sections were measured for three angles of deuteron emission in the range of projectile-deuteron energies E_d between 12 and 15.3 MeV. The double-differential cross sections for the reaction in question were measured for the 2⁺ state of the ¹²C nucleus at 4.44 MeV, and the angular dependences of the even spin-tensor components of the density matrix were determined, along with the angular dependences of the populations of magnetic sublevels and the components of the tensors of multipole-moment orientation. These experimental results are compared with their theoretical counterparts obtained under the assumption of various reaction mechanisms, including collective interaction, heavy-particle stripping, a two-step mechanism that takes into account the delay in the interaction, and the mechanism of compound-nucleus formation

[en] The supraatomic structure of single crystals of synthetic quartz was studied by thermal neutron small-angle scattering in the initial state (dislocation densities 54 and 570 cm^-2) and after irradiation in the WWR-M reactor (Petersburg Nuclear Physics Institute) by fast neutrons with energies E_n > 0.1 MeV at fluences F_n = 0.2 x 10¹⁷ -5 x 10¹⁸ neutrons/cm². It is established that fast neutrons form point, linear, and volume defects in the lattice throughout the entire volume of a sample. Large-volume structures-amorphous-phase nuclei-reach sizes of ∼100 nm in quartz, while occupying a small total volume of ∼0.3% even at the maximum fluence 5 x 10¹⁸ neutrons/cm². The main fraction of the damaged volume (up to 5%) corresponds to point (with a radius of gyration of 1-2 nm) and linear defects, giving a comparable contribution (∼1-4%). The extended linear structures with a radius of 2 nm, even at a moderate fluence of 7.7 x 10¹⁷ neutrons/cm², have a significant total length per volume unit (∼10¹¹ cm/cm³) and can form a connected network with a cell ∼30 nm in size in the sample. Foreign atoms and molecules can migrate through channels of this network

[en] The supraatomic structure of single crystals of synthetic quartz in the initial state with a dislocation density of 570 cm^-2 and after irradiation in the VVR-M reactor at the Petersburg Nuclear Physics Institute with fast neutrons having the energy E_n > 1 MeV in the range of fluences F_n = 7.7 x 10¹⁷ -2.1 x 10²⁰ neutrons/cm² has been studied by small-angle scattering of thermal neutrons. It is established that fast neutrons form point, linear, and volume lattice defects throughout the entire sample volume. Large-volume structures (nuclei of the amorphous phase) in quartz, reaching ∼100 nm in size, occupy a small total volume (∼1.5%) even at the maximum fluence 2.1 x 10²⁰ neutrons/cm². The majority of damage is related to the point defects with the radius of gyration of 1-2 nm and linear defects, which give comparable contributions up to several percent