Eurasian Journal of Physics and Functional Materials

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Vol 3, No 1 (2019)
10-17 27

The mass and total kinetic energy distributions of the fission fragments in the fission of even-even isotopes of superheavy elements from Hs (Z=108) to Og (Z=118) are estimated using a pre-scission point model. We restrict to nuclei for which spontaneous fission has been experimentally observed. The potential energy surfaces are calculated with Strutinsky’s shell correction procedure. The parametrization of the nuclear shapes is based on Cassini ovals. For the just before scission configuration we fix α = 0.98 , what corresponds to rneck ≈ 2 fm, and take into account another four deformation parameters: α1 , α1 , α4 , α6 . The fragment-mass distributions are estimated supposing they are due to thermal fluctuations in the mass asymmetry degree of freedom just before scission. The influence of the excitation energy of the fissioning system on these distributions is studied. The distributions of the total kinetic energy (TKE) of the fragments are also calculated (in the point-charge approximation). In Hs, Ds and Cn isotopes a transition from symmetric to asymmetric fission is predicted with increasing neutron number N (at N ≈ 168). Super-symmetric fission ocurs at N ≈ 160. When the excitation energy increases from 0 to 30 MeV, the peaks (one or two) of the mass distributions become only slightly wider. The first two moments of the TKE distributions are displayed as a function of the mass number A of the fissioning nucleus. A slow decrease of the average energy and a minimum of the width (at N ≈ 162) is found.

18-23 30

The emerging experimental program with brilliant gamma beams at the Extreme Light Infrastructure - Nuclear Physics facility (ELI-NP) is presented with emphasis on the prepared day-one experiments. Ex- periments at ELI-NP will cover nuclear resonance fluorescence measurements, studies of large-amplitude motions in nuclei, photo-fission and photonuclear reactions of astrophysics interest, and measurements of photonuclear reaction cross sections. The physics cases of the flagship experiments at ELI-NP and the performance of the related instruments, which are under construction for their realization, are discussed.

24-30 30

Charged-particle trajectories in the MAVR high resolution magnetic spectrometer are simulated. The latter has been constructed at the U400 accelerator for purifying the incident beam and identifying the products of nuclear reactions induced by the beams of stable and radioactive nuclei. In this paper we present the MAVRPC++ software package, aimed at reconstructing the spectrometer focal plane, optimizing the fields of quadrupole and dipole magnets, and estimating the solid-angle acceptance for secondary particles.

31-39 26

Theoretical description of the experimental data on the formation of various isotopes in reactions (3He+194Pt) and (3He+45Sc) requires taking into account neutron and proton transfer channels, as well as fusion-evaporation channels. To calculate the probabilities of nucleon transfer as well as transfer cross sections the time-dependent Schrodinger equation (TDSE) has been solved numerically. Fusion- evaporation was taken into account using the statistical model code of the NRV web knowledge base. Results of calculations are in agreement with experimental data.

46-52 31

The commissioning of the new fragment separator ACCULINNA-2 at FLNR JINR is accomplished. The separator is destined to expand the possibilities in studies of dripline nuclei performed with the exotic secondary radioactive ion beams (RIBs) at energies of (5 - 50) AMeV. The projected high transmission and purification level were confirmed experimentally for a number of RIBs in the last two years. The ACCULINNA-2 setup will become a backbone facility at FLNR for the research in the field of light exotic nuclei. This report shows the current status of the separator, describes the obtained RIBs parameters and first experiments as well, provides the overview of the developing detection, monitoring and control subsystems.

53-57 31

Differential cross sections of elastic scattering of12,14Be on12C and protons are analyzed within the microscopic model of the optical potential (OP). The microscopic OP consists of the double folding real part and the imaginary part which is constructed using the high energy approximation theory. The OP depends on the nuclear density distributions of12,14Be and thus, their microscopic models are tested in our study.

58-62 35

In the last years we carried out several experiments aimed to investigate properties of short-lived SF isotopes. The neutron-deficient isotopes of nobelium were produced in fusion-evaporation reactions using206,208Pb targets and an intense48Ca-beam. Fusion-evaporation residues were separated by the SHELS separator and implanted into a large-area double-sided (48 × 48) strip silicon detector surrounded by3He-based neutron counters. Half-lives and decay branching ratios for252,254No isotopes were measured. The average number of neutrons per spontaneous fission of254No determined for the first time.

63-70 30

The PITRAP-project for mass measurements of exotic nuclides is based on the use of high flux-reactor PIK and a high precision Penning trap mass spectrometry. This combination gives a synergy in exploration of different problems of fundamental physics: from astrophysics to neutrino physics.

71-83 30

Experiments in preparation for search for uranium ternary fission by means of nuclear track emulsion are summarized. The study will be focused on the possible involvement of the unstable nucleus8Be in the suggested scenario of the collinear tri-partition in the fission.

84-90 36

The GALILEO γ -ray spectrometer has been constructed at the Legnaro National Laboratory of INFN (LNL-INFN). It can be coupled to advanced ancillary devices which allows nuclear structure studies employing the variety of in-beam γ -ray spectroscopy methods. Such studies benefit from reactions induced by the intense stable beams delivered by the Tandem-ALPI-PIAVE accelerator complex and by the radioactive beams which will be provided by the SPES facility. In this paper we outline two experiments performed within the experimental campaign at GALILEO coupled to the EUCLIDES Si-ball and the Neutron Wall array. The first one was aimed at spectroscopic studies in A=31 mirror nuclei and the second one at measurements of lifetimes of excited states in nuclei in the vicinity of 100 Sn.

91-98 29

The paper presents the results of a study of the effect of proton and ion radiation on structural changes in nitride ceramics, which have a high potential for using as a structural material for GenIV nuclear reactors. Proton beams with an energy of 1.5 MeV and low-energy helium (He2+) and carbon (C2+) ions with an energy of 40 keV were used, to simulate defect formation and to estimate ceramics radiation resistance. According to the data obtained, it has been established that AlN nitride ceramics have high radiation resistance to the effects of proton radiation. While under irradiation with C2+ ions, the observed degradation of the surface layer is due to the accumulation of carbon in the structure with the subsequent formation of impurity carbide inclusions. It is established that the accumulation of slightly soluble ions of helium and carbon in the structure of the surface layer leads to an increase in the strain and distortion of crystal lattice due to introducing ions into the interstitial lattice and breaking chemical and crystalline bonds.

ISSN 2522-9869 (Print)
ISSN 2616-8537 (Online)