We presented a setup created on the RADEX neutron channel at the Institute for Nuclear Research of the Russian Academy of Sciences to study the properties of highly excited states of light nuclei. The first experiment was carried out on the setup to determine the cluster structure of highly excited states of the 6Li nucleus in the reaction 6Li(n, 3He n)3H at a neutron energy of 50 ± 5 MeV. Several variants of the data collection system have been tested. A preliminary spectrum of the excitation energies of the 6Li nucleus has been obtained.

The authors offer works using the MMF INR RAS neutron channel to study the cluster structures in light nuclei, in particular, 𝛼-4n-𝛼 and 8Be-4n in the highly excited state 12Be*. This needs the registration of charged particles from the 12Be* 𝛽-decay during its formation in the 𝑛+13C reaction in the intervals between cascade neutron pulses. The paper presents the first results of an experiment on measuring the spectra and time distributions of gamma-quanta and neutrons using a proton beam of 50 Hz and a duration of 0.3 𝜇s.

The paper presents the results of test measurements to determine the possibilities of studying the cluster structure of highly excited states of the 6Li nucleus in the 6Li(𝑛, 3He 𝑛) 3H reaction on the RADEX neutron channel of the Institute for Nuclear Research of the Russian Academy of Sciences. In the experiment, scattered neutrons were detected in coincidence with the decay products of highly excited states (helium-3). The first experimental data on the excitation energy of the 6Li nucleus have been obtained.

A change in the shape of the pulse is observed for fully depleted silicon surface-barrier detectors. This change depends on the condition of complete absorption or the passing of a charged particle through the detector. A way of obtaining such information is proposed for separating forward and reverse directions in loci on two-dimensional ΔE–E diagrams, with parameterization similar to the widely used PSD approach to separating γ-quanta and neutrons.

Standard spectrometric α-particle source Ra-226 is used to measure the dependences of the time parameters of silicon detectors on their bias voltage. The duration and the shape of the front of the signal are determined along with the amplitude and time resolutions. The time resolution of the setup for studying reactions on light nuclei is determined and calibrated. Recommendations are given for the optimum sequence of such measurements.

The neutron spectrum produced in the γ +9Be → 8Be + n reaction at different boundary energies of the photon spectrum is modeled in order to examine the possibility of measuring nuclear cross sections with fast quasi-monoenergetic neutron beams of the W–Be photoneutron source at the Institute for Nuclear Research. The obtained spectra are used to model the response of a hydrogen-containing detector to neutrons in the n + 1H → n + p reaction. An experimental setup for determining the energy spectrum of neutrons of the W–Be source is constructed. The spectra of secondary neutrons detected in an active hydrogen-containing target irradiated with neutrons are measured and compared to the ones modeled.

A kinematic simulation of the γ + 9Be → 8Be + n reaction is performed, in which the beam of quasi-monoenergetic photons is considered the input beam. The possibility of obtaining a beam of quasimonoenergetic neutrons at the photoneutron source of the Russian Academy of Sciences’ Institute for Nuclear Research is demonstrated. The efficiency of obtaining quasi-monoenergetic neutrons and the effect the quasi-monochromatization parameters of the photon bremsstrahlung spectra have on the neutron energy distribution are investigated.

Low-energy (0.04–3.0 MeV) neutron data for even-even 58–64Ni and 64–70Zn isotopes are analyzed in terms of the coupled channel optical model (CCOM) as a function of N p N n, where N p(N n) are the numbers of valent nucleons (particles or holes), and consider the relationship between the diffuseness parameter obtained from CCOM calculations and the value of the N p N n function. Considering the Ni and Zn isotope chains with the traditional magic number Z = 28 and the nontraditional N = 38 proves the existence of N = 28–38 subshells. The results from our analysis indicate the possible existence of the nontraditional magic nucleus 30 68 Zn38.

An interaction potential with a radial dependence in the Woods-Saxon form is used to describe low energy neutron data in the context of the coupled channel optical model. A single value of the diffuseness parameter was used for even-even nuclides over a wide range of A : a = 0.65 fm. Traditional and nontraditional magic and nonspherical nuclei were exceptions. The deviations can be used to find or verify the existence of nontraditional magic numbers.

Low-energy neutron data for even-even isotopes 1 142–150 Nd are considered. It is shown that the diffuseness parameter noticeably changes in going from one isotope to another (from a = 0.55 fm for 142 Nd to a = 0.75 fm for 150 Nd), which agrees with the theoretical indications of a decrease in the skin thickness for nuclei with closed shells. The analysis points to the possible existence of the semimagic number Z = 58.

It is shown that experimental values of the cross sections of inelastic low-energy neutron scattering on even-even nuclei together with the description of these cross sections in the framework of the coupled channel optical model may be considered as a reliable method for finding nuclei with a semimagic number (or numbers) of nucleons. Some examples of the application of this method are considered.

A unified description of the experimental data on low-energy neutron scattering on even Ru and Pd isotopes has been obtained within the rotational version of the coupled-channel optical model. The parameters of this model for Ru and Pd nuclei coincide with the values obtained by us in description of the neutron data on the nuclei in the range 46 ≤ A ≤ 246. It is shown that the coupled-channel optical model makes it possible to obtain unified description of the neutron interaction with spherical, deformed, and transition even-even nuclei.

Neutron strength functions and potential-scattering lengths for neutron interactions with even-even spherical nuclei have been calculated within the two-photon version of the coupled-channel optical model (CCOM). The results of these calculations have been found to comply well with experimental data. This agreement has been obtained with a single set of CCOM parameters that were deduced from a global fit to data on neutron cross sections (including data on total cross sections, cross sections for inelastic scattering accompanied by the excitation of 2(1)(+) levels, and differential elastic and inelastic cross sections) over the energy range 0.07-3.00 MeV.