Исследована роль замкнутых и деформированных протонных и нейтронных оболочек в делении ядер \({}^{248}\) Cf и \({}^{254,256}\) Fm с энергией возбуждения от 40 до 56 МэВ. Массово-энергетические распределения осколков деления этих ядер, образованных в реакциях \({}^{16}\textrm{O}+^{232}\) Th и \({}^{16,18}\textrm{O}+^{238}\) U, были измерены при энергиях налетающих ионов вблизи кулоновского барьера с помощью времяпролетного спектрометра CORSET. Показано, что во всех исследованных реакциях повышенный выход осколков в районе массы 100 а.е.м. связан с влиянием деформированной протонной оболочки \(Z\sim 38\) . Обнаружено проявление SuperShort-моды в делении \({}^{256}\) Fm при энергии возбуждения составного ядра 40 МэВ.

Mass and energy distribution of fission fragments of 236U* nuclei, formed in the reaction 232Th(α,f) at incident alpha energy of 29 MeV were studied to reveal the influence of shell effects. The experiment was carried out by 2E method at U-150M accelerator at Institute of Nuclear Physics, Almaty city. Acquired experimental data was decomposed into yields of separate shells, including deformed shells, assuming that the shell yield has the form of gauss distribution. The manifestation of deformed shells N84, Z52 and deformed shells Z36, Z38 was revealed.

Background: Shell effects have been found to influence both the compound nuclear fission (CNF) and quasifission processes. Besides quasifission processes, which fission modes remain active at excitation energy (E*) as high as 56 MeV should be investigated. Purpose: We investigate the signatures of fission modes in Fm-254 populated by O-16 + U-238 through the mass distribution (MD) and total kinetic energy distribution (TKED). Method: The mass-total kinetic energy distributions (M-TKED) of fission fragments of the reaction O-16 + U-238 have been measured at two laboratory energies E-lab = 89 and 101 MeV. The spontaneous fission (SF) of Fm-254, one-dimensional (1D) fragment MD, and two-dimensional (2D) M-TKEDs of O-16 + U-238 have been described by the multimodal random neck rupture (MM-RNR) model. Results: Channel probabilities and the characteristics of different fission modes are obtained and discussed in detail. The enhancement observed in the mass yield (approximate to 10(-2) %) in the region 60-70 u for the light fragments at E* approximate to 45 MeV goes away at the higher E* approximate to 56 MeV. The heavy fragments of S1 and S2 modes are found to be associated with Z approximate to 53 and Z approximate to 56 shells, respectively. The slope of asymmetric to symmetric fission yields (when plotted against E*) of O-16 + U-238 is found to be similar to that of previously reported O-18 + Pb-208. Conclusions: Analysis of 2D M-TKED data by the MM-RNR model reveals the possible presence of fission modes in O-16 + U-238. The liquid-drop-like broad symmetric SL mode is found to peak at a lower energy than predicted by the Viola systematic, which matches mostly with that of Standard 2 mode. No signature of asymmetric quasifission is observed. The MD widths show a linear dependence with the measured energies.

The role of closed and deformed proton and neutron shells in the fission of Cf-248 and Fm-254,Fm-256 nuclei at excitation energies from 40 to 56 MeV is studied. The mass-energy distributions of fission fragments of these nuclei formed in the O-16 + Th-232 and O-16,O-18 + U-238 reactions at projectile-ion energies close to the Coulomb barrier are measured by means of the CORSET time-of-flight spectrometer. It is shown that, in all of the reactions under study, an enhanced yield of fragments in the mass region around 100 a.m.u. is due to the effect of the Z similar to 38 deformed proton shell. A manifestation of a supershort mode is found in the fission of Fm-256 at the compound-nucleus excitation energy of 40 MeV.

A method for determining the etching rate of phosphate glass irradiated with heavy ions is presented. The etching rates in the track area and in the undamaged material area are quantitatively estimated. The work is aimed at studying the possibility of determining the charges of synthesized superheavy ions in phosphate glass detectors at the Factory of Superheavy Elements at the Joint Institute for Nuclear Research.

The role of closed and deformed proton and neutron shells in the fission of ^248 Cf and ^254,256 Fm nuclei at excitation energies from 40 to 56 MeV is studied. The mass–energy distributions of fission fragments of these nuclei formed in the ^16O + ^232 Th and ^16,18O + ^238 U reactions at projectile-ion energies close to the Coulomb barrier are measured by means of the CORSET time-of-flight spectrometer. It is shown that, in all of the reactions under study, an enhanced yield of fragments in the mass region around 100 a.m.u. is due to the effect of the Z∼ 38 deformed proton shell. A manifestation of a supershort mode is found in the fission of ^256 Fm at the compound-nucleus excitation energy of 40 MeV.

The characteristics of heavy ion tracks in phosphate glasses after irradiation under various temperature conditions are presented. Calibration experiments are performed to obtain the dependence of the parameters of the etched tracks on the sample heating temperature and time and on the moment of heating a sample in relation to irradiation and etching. To effectively identify the ion charges, the stability of reproducing the optimum chemical etching conditions (etching chemical solution composition, concentration, etching time) is strictly observed in processing irradiated glasses. The results obtained allow us to conclude that phosphate glasses can be effectively used to detect and identify the superheavy nuclei synthesized at the Factory of Superheavy Elements of the Joint Institute for Nuclear Research (JINR).

The detection and identification of heavy ions in phosphate glasses is based on an analysis of geometric parameters of tracks that manifest themselves upon the etching of irradiated glasses in a special solution. The shape and size of emerging tracks depend both on the parameters of the ions being studied (charge, energy, and angle of incidence) and on the etching conditions (etchant composition and concentration and etching time). Phosphate glass belongs to the class of solid-state tracking detectors whose principle of operation relies on the fact that multiply charged particles destroy a local solid-state structure along their trajectory. This local damage can be intensified by means of subsequent etching, whereby the tracks under study are visualized. The damaged parts of the material react with an etchant more intensely than intact parts do. This reaction leads to the formation of characteristic etching cones.The radiation damage of the material is proportional, as well as the specific energy loss of charged particles is, to the square of the particle charge and also depends on the particle speed.

The system size problems are the important component of the multi-particle dynamics, which, however, is not sufficiently taken into account in the cosmic ray researches. Therefore, in addition to a broad and important program of new сollider and target experiments to study the interactions of protons with light nuclei, we propose to consider the features of multi-particle processes on light nuclei. In the work these problems are studied in the centrality selected interactions of light – (C, O, Ne) – (beam) and heavy – (Au, Pb) – (beam) ions with light – (C/N/O) – (target) and heavy – (Ag/Br) – (target) nuclei on the data of JINR-AGS-SPS target emulsion experiments with limited statistics. In order to reveal the possible system structure dependence, the analyses of E-by-E fluctuations on the longitudinal event shape and multiplicity are performed in two directions: on vertically, – for different (beam-target) pairs of nuclei under certain impact parameters, and on horizontally, – for the same (beam-target) pairs of nuclei on different impact parameters. The strong fluctuation enhancement for the central collisions of (C, O, Ne) – beam + (C/N/O) – target was interpreted as the sign of intrinsic virtual alpha-clustering in light nuclei.

The experimental data on mass and energy distributions of fission fragments of compound nuclei 236U, 237, 240, 242Pu, 244Cm formed in 232Th (α, f), 233, 236, 238U (α, f) и 240Pu (α, f) reactions at incident alpha particle energies of Eα = 29 MeV is presented. Excitation energy of the compound nuclei for all reactions was 21±2 MeV. Experiments were carried on the isochronous cyclotrone U-150M at The Institute of Nuclear Physics, Almaty city.тIt was shown that behavior of mass distributions Y(m) depends mainly on proton number in heavy and light fragmentsтthat are being formed. For isotopes of one element (237, 240, 242 Pu) charge distributions ofтfragments Y(Z) are almost the same. The discovered differences between behaviors of fragments mass distributions Y(m) and their energy distributions (Ek(m) и σ2(m)) points to these characteristics being formed at a different stages of fission process. Kinetic energy is determined by the conditions at rupture point, mass distributions are formed at earlier stages of fission process, when future fragments are still connected by a thick neck.

A better understanding of initial conditions of nuclear interactions is one of the most important heavy ion physics problems. The paper considers these problems in the centrality selected interactions of light (C, O, Ne) – (beam) and heavy (Au, Pb) – (beam) ions with light (C/N/O) – (target) and heavy (Ag/Br) – (target) nuclei using the data of JINR-AGS-SPS target emulsion experiments with limited statistics. To reveal a possible system structure dependence, the analyses of E-by-E fluctuations on the longitudinal event shape and multiplicity have been performed, vertically and horizontally.

Mass–energy distributions of fission fragments are measured in the proton energy region of 7 to 55 MeV in order to study shell effects in the fissioning of 232Th nuclei induced by protons at low and intermediate energies. Experiments at proton energies of 13 to 55 MeV are performed using proton beams from the K-130 cyclotron at the University of Jyväskylä (Finland) using the CORSET two-armed time-of-flight spectrometer. Experiments at proton energies of 7, 10, and 13 MeV are performed using the beam from the U‒150M cyclotron at the Institute of Nuclear Physics in Almaty (Kazakhstan) using a 2Е spectrometer for detecting fission fragments. It is found that the yield of symmetric fragments falls along with the proton energy, while the yield of asymmetric fragments rises. Deep below the Coulomb barrier at the lowest proton energy of 7 MeV, an increased yield of fission fragments is observed in the region of 60−70 a.m.u., which corresponds to the superasymmetric mode of fission.

The problem of the dependence of multiparticle reaction-product formation on the interactionregion size is considered both at cosmic-ray and accelerator energies. In cosmic rays, a comparative analysis of interactions induced by protons and light nuclei was performed on the basis of data obtained by the Stratosphere Collaboration. At accelerator energies, the problem was studied by employing data of the EMU Collaboration. The results revealed a substantial distinction between the production processes in these event groups. An analysis of interactions between light nuclei, (C, O, Ne) + (C/N/O); between intermediate and light nuclei, (Si, S) + (C/N/O); and between heavy nuclei, (Au, Pb) + (Ag/Br), showed that there is a sizable enhancement of fluctuations as the size of the interaction region becomes smaller. A sharp growth of multiplicity and pseudorapidity correlations in the most central interactions, (C, O, Ne) + (C/N/O), is interpreted as a manifestation of internal virtual alpha-particle clustering of light nuclei.

The system size dependence for multiparticle processes has been recognized in both cosmic ray (“Stratosphere” collaboration) and at accelerator (“EMU” collaboration) experiments. The strong enhancement in multiplicity fluctuations for the most central light-light – (C, O, Ne) + (C/N/O) – collisions has been revealed at JINR-AGS-SPS energies. The sharp difference of light nuclear interactions are interpreted as the sign of intrinsic alpha-clustering in light nuclei.

The mass-energy distributions and cross sections of proton-induced fission of 232 Th have been measured at the proton energies of 7, 10, 13, 20, 40, and 55 MeV. Experiments were carried out at the proton beam of the K-130 cyclotron of the JYFL Accelerator Laboratory of the University of Jyväskylä and U-150m cyclotron of the Institute of Nuclear Physics, Ministry of Energy of the Republic of Kazakhstan. The yields of fission fragments in the mass range A = 60–170 a.m.u. have been measured up to the level of 10−4%. The three humped shape of the mass distribution up has been observed at higher proton energies. The contribution of the symmetric component grows up with increasing proton incident energy; although even at 55 MeV of proton energy the shoulders in the mass energy distribution clearly indicate the asymmetric fission peaks. Evolution of shell structure was observed in the fission fragment mass distributions even at high excitation energy.

The interactions of cosmic ray light nuclei and protons with different targets were studied at "Stratosphere" experiment at energies above 10 TeV in the Lab system. The results show that in the rare events, produced by alpha-particles and light nuclei, transverse momentum spectra of secondary γ-quanta in the soft region (up to 2 GeV/c) have exponential character with large values of inverse slope of the distributions: TA ∼ 0,8 GeV/c. On the contrary, in the proton interactions the slope is essentially smaller Tp ∼ 0,2 GeV/c. For charged secondary particles the high order intermittency analyses have again demonstrated the large difference between events produced by protons and nuclei. So, essential system size dependence in the forward production dynamics was obtained with the limited statistics. Such processes with a large energy flux in the forward direction are difficult to measure at the Collider experiments. Current Large Hadron Collider forward (LHCf) experiment and future RHICf experiment are very important to give the information about the dynamics of strong interaction in both , high energy heavy ion physics and in high energy cosmic rays. However, there are different serious problems to compare directly the results of Stratosphere and LHCf experiments, including problem with different kinematics and the requirement for the study of the light nuclei interactions at the Colliders as well. In the present paper, as the first step, we compare the data of Stratosphere and LHCf experiments for PT spectra of γ-quanta and neutral pions production in the proton-induced interactions in commensurable rapidity intervals.