The H7 system was populated in the H2(He8,He3)H7 reaction with a 26 AMeV He8 beam. The H7 missing mass energy spectrum, the H3 energy and angular distributions in the H7 decay frame were ...reconstructed. The H7 missing mass spectrum shows a peak, which can be interpreted either as unresolved 5/2+ and 3/2+ doublet or one of these states at 6.5(5) MeV. The data also provide indications of the 1/2+ ground state of H7 located at 1.8(5) MeV with quite a low population cross section of ∼25 μb/sr within angular range θc.m.≃(17°-27°).
The proton and deuteron pickup reactions
and
were studied with the
radioactive beam produced by the new fragment separator ACCULINNA-2 at FLNR, JINR. These measurements were initially motivated as ...the test reactions intended for the elucidation of results obtained in the study of the extremely neutron-rich
H and
H systems created in the
and
reactions with the use of the same setup. In the
reaction the
Li ground-state (
) and its first excited state (2.69 MeV,
) were identified in the low-energy region of its excitation spectrum. The differential cross sections for the
population were extracted at the forward center-of-mass angles (
) and compared with the FRESCO calculations. Spectroscopic factor of
, derived by a model suggesting the
clustering was found in accord with the experimental data. The energy spectrum of
Li populated in the
reaction shows the strong peak which corresponds to the excitation of the second excited state of
Li (2.25 MeV,
). The fact that the ground and the first excited states of
Li were not observed in this reaction is consistent with the shell-model structure of the nuclei involved.
Setup fitting the requirements for the detailed study of the five-body decay of the
7
H nucleus obtained as a result of the proton transfer from the
8
He projectiles to the deuterium target nuclei is ...being built at the radioactive beam line of ACCULINNA-2 separator in the G.N. Flerov Laboratory of Nuclear Reactions. Described here is the assembly of 100 BC-404 plastic scintillators, intended for neutron detection, the annular Si detector telescope for the
3
He recoils, and the detector array providing the Δ
E
–
E
-TOF registration of
3
H nuclei emitted at the
7
H decay. Results obtained by the Monte Carlo simulations made for the energy values and flight passes of all these particles are given together with the luminosity expected for the discussed experiments.
Quasi-elastic, multi-nucleon transfer reactions induced by the radioactive-ion beams with energy 4–6 MeV/u allow one to produce moderately excited neutron-rich nuclei with atomic numbers
. This ...offers a new approach to the study of the so far unknown nuclei in the neighborhood of the recently discovered island of super-heavy elements and to the acquirement of new data specifying significant fission characteristics of the actinide nuclei appearing in the r-process nucleosythesis.
The transport parameters were determined for the
18
O isotope (in the form of H
2
18
O), the Br
−
ion, and atrazine in intact columns of allophanic Andosol (Mexico State, Mexico). A one-dimensional ...model for the convective-dispersive transport of chemicals with account for the decomposition and equilibrium adsorption (HYDRUS-1D), which is widely applied for assessing the risk of the chemical and bacterial contamination of natural waters, was used. The model parameters were obtained by solving the inverse problem on the basis of laboratory experiments on the transport of the
18
O isotope, the Br
−
ion, and atrazine in intact soil columns at a fixed filtration velocity. The hydrodynamic dispersion parameters determined for the
18
O and Br
−
ions in one column were of the same order of magnitude, and those for atrazine were higher by 3–4 times. The obtained parameters were used to calculate the transport of these substances in another column with different values of the water content and filtration velocity. The transport process was adequately described only for the
18
O isotope. In the case of the Br
−
ion, the model significantly underestimated the transport velocity; for atrazine, its peak concentration in the column was overestimated. The column study of the transport of the three chemical compounds showed that transport parameters could not be reliably predicted from the results of a single experiment, even when several compounds were used in this experiment.
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.
A neutron spectrometer based on stilbene crystals has been developed by the Flerov Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research (Dubna, Russia). The timing resolution ...is determined as a function of the signal amplitude (σ
T
= 0.18 ns at an amplitude of 1 MeV in the electron equivalent). The measured energy resolution of the detecting modules for γ rays is σ
E
/
E
= 4.5% at
E
= 1 MeV. The quality of the
n
–γ discrimination is investigated. It is shown that reliable discrimination is possible, beginning with a deposited energy of 100 keV in the electron equivalent, which corresponds to the kinetic energy of recoil protons of ∼700 keV. The neutron spectrometer helps to significantly expand the experimental capabilities and to carry out correlation experiments with radioactive beams on the ACCULINNA-2 fragment separator at a new level of quality.
The one-neutron transfer
2
H(
9
Li,
p
)
10
Li reaction has been investigated at 29
A
MeV incident energy at the ACCULINNA-2 facility (Flerov Laboratory of Nuclear Reactions, Joint Institute for ...Nuclear Research). The setup has been used in order to detect the recoil protons at backward angles in coincidences with the outgoing
9
Li and neutrons from the
10
Li decay at forward angles. This setup allows to study the
10
Li emitted in the crucial region at forward angles in the center of mass. The preliminary results in the part of the analysis of double proton–
9
Li coincidence are reported.
Investigation of the
7
H-system in the experiment conducted at the fragment separator ACCULINNA-2 in the
8
He(
2
H,
3
He)
7
H reaction requires to detect the recoil
3
He ions with energy down to 6 ...MeV. For this purpose two
particle telescopes are used, with each telescope having in front a thin (20-μm) Si strip detector (
). The maps of thickness heterogeneity of the thin detectors were determined by measuring the energy losses of the
226
Ra α-particles. The adopted thickness normalization method provides a good identification of the
3
He nuclei being recorded in the presence of a high
4
He background. Two approaches were used for calculating the energy losses of the identified
3
He and
4
He reaction ejectiles and reconstructing their energy values available at the exit from the deuterium target. The developed techniques were applied for the
7
H missing-mass reconstruction.
Search for the population of the low-energy continuum of tetraneutron system was performed for reactions of the \(^{8}\)He beam on deuterium target. These studies are performed for the data I.A. ...Muzalevskii et al., Phys. Rev. C 103, 044313 (2021), previously used for the studies of \(^{7}\)H and \(^{6}\)H in the \(^2\text{H}(^8\text{He},{^3\text{He}})^{7}\)H and \(^2\text{H}(^8\text{He},{^4\text{He}})^{6}\)H reactions. Evidence for a hump in the \(^4n\) continuum at \(3.5 \pm 0.7\) and \(3.2 \pm 0.8\) MeV, was observed in the \(^2\)H(\(^8\)He,\(^6\)Li)\(^4\)n and \(^2\)H(\(^8\)He,\(^3\)He)\(^7\)H\(\rightarrow ^3\)H+\(^4\)n reactions, respectively. The observed statistics is quite low (6 and up to 40 events) corresponding to very low cross sections of few microbarns or tens of microbarns. The background conditions for the \(^2\)H(\(^8\)He,\(^6\)Li)\(^4n\) reaction are shown to be good, favoring the physical nature of the observed events. The \(^2\)H(\(^8\)He,\(^3\)He)\(^7\)H\(\rightarrow ^3\)H+\(^4n\) process transforms to the \(^2\)H(\(^8\)He,\(^6\)Li\(^{\ast})^4n\) reaction in the limit of the highest \(^7\)H decay energies. The population of the low-energy region in the \(^{4}\)n spectrum is found to be perfectly correlated with the population of the lowest \(^{6}\)Li states in the \(^{3}\)He+\(^{3}\)H continuum. Theoretical calculations of \(^{8}\)He in a five-body \(\alpha\)+\(4n\) and of \(^{4}\)n in a four-body hyperspherical models are presented. The \(^{8}\)He wave function is shown to contain strong specific correlations, which may give rise to very low-energy structures in tetraneutron continuum in extreme-peripheral reaction scenarios.
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