The new experimental setup has been built at the 11b channel of the IBR-2 research reactor at FLNP, JINR, to study the elemental composition of samples by registration of prompt gamma emission during thermal neutron capture. The setup consists of a curved mirror neutron guide and a radiation-resistant HPGe high-purity germanium detector. The detector is surrounded by lead shielding to suppress the natural background gamma level. The sample is placed in a vacuum channel and surrounded by a LiF shield to suppress the gamma background generated by scattered neutrons. This work presents characteristics of the experimental setup. An example of hydrogen concentration determining in a diamond powder made by detonation synthesis is given and on its basis, the sensitivity of the setup is calculated being ∼4 μg.

The TALYS 1.9 program is used to calculate cross sections of processes that occur during the scattering of fast neutrons on 48 Ti, 52 Cr, and 56 Fe isotopes. Results from model calculations are compared to data obtained in the TANGRA project using tagged neutrons from the yields of γ-quanta for Ti, Cr, and Fe isotopes, and the results from earlier experiments. Analysis of the model description’s sensitivity to the choice of the direct reaction mechanism shows the most informative characteristic from this viewpoint is the differential cross section of inelastic scattering.

The neutron reflectometry method is used to measure the spatial profile of the potential of interaction between neutrons and a medium. At the interface between media, the interaction potential is the sum of potentials of individual isotopes. Neutrons and gamma radiation emitted by the atomic nuclei of an element are recorded to determine the potential of interaction between neutrons and individual isotopes. Channels for the recording of gamma quanta and spin-flipped neutrons are created using a REMUR spectrometer. Channel testing results are given, model calculations of the neutron absorption coefficients are carried out, and prospects related to the recording of gamma quanta and polarized neutrons are discussed.

A study of the reaction of inelastic scattering of 14.1 MeV neutrons by 23 Na nuclei was carried out at the TANGRA facility using the tagged neutron method. In this work, the energies of visible g-transitions are determined, the yields of g -quanta are obtained, the angular distributions of g -quanta for 23 Na are measured. The results obtained are in good agreement with the data of other published experimental works.

The reaction induced by the inelastic scattering of 14.1-MeV neutrons on chromium nuclei is studied by means of the tagged-neutron method at the TANGRA (TAgged Neutrons and Gamma RAys) facility deployed at Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, and based on the ING-27 standard neutron generator. The energies of visible gamma transitions occurring in various reactions of neutron interaction with chromium nuclei and their partial cross sections are determined. The results obtained by measuring the angular distribution of gamma rays for $${}^{52}$$Cr are analyzed and are compared with respective results of other experimental studies available in the literature.

This paper is dedicated to n+C-12, n+Mg-24, n+Cr-52 -reactions investigation at 14.1 MeV neutron energy. Characteristics of these reactions have been calculated using TALYS code to estimate perspectives of using of this code in data interpretation in the TANGRA project. This project is performed in Frank Laboratory of Neutron Physics (FLNP JINR) to investigate properties of (n,xy)-type reactions, important for fundamental and practical applications.

Neutron reflectometry is a method for measuring the spatial profile of the neutron interaction potential with the medium. The interaction potential is the sum of neutron interaction potentials with separate isotopes of the medium. To determine the neutron interaction potential with the structure units, secondary radiation is simultaneously registered with neutrons. Channels for registering secondary radiation of charged particles, gamma rays and neutrons, having experienced spin flip, have been developed on the REMUR spectrometer of the IBR-2 reactor in Dubna (Russia). The necessity of registering secondary radiation in neutron reflectometry is justified, a method developed for measuring secondary radiation is described and the results of testing channels for registering secondary radiation on the REMUR spectrometer are presented in the paper.

An ionization chamber is installed to the REMUR neutron spectrometer, situated at channel no. 8 of the IBR-2. A layered structure containing a layer of the isotope under study with a thickness of several nanometers is placed into the chamber. A neutron beam enters the chamber and is incident on the structure. The reflected neutron beam and the neutron beam transmitted through the structure are recorded by a detector located outside the chamber. A fraction of neutrons incident on the structure is captured by the nuclei of the isotope under study. As a result, secondary radiation is generated in the form of charged particles, which are recorded by the ionization chamber. The dependences of the neutron and charged particle intensities on the transmitted wave vector of neutrons are used to determine the spatial dependences of the potential of interaction between neutrons with the entire structure and with a layer of the isotope under study. The neutron spectrometer in grazing geometry, using which the neutrons and charged particles are recorded in studying the layered structures, is described. The results of spectrometer testing with the use of structures containing the 6Li isotope are given.

A series of experiments has been conducted at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in order to study the possibility of determining the moisture content of coke using a standard neutron source. The proposed method is based on a measurement of the spectrum of prompt γ rays emitted when samples are irradiated by fast and/or thermal neutrons. The moisture content is determined from the area of the peaks of characteristic γ rays produced in the radiative capture of thermal neutrons by the proton (Eγ = 2.223 MeV) and inelastic scattering of fast neutrons by 16O (Eγ = 6.109 MeV). The 239Pu–Be neutron source (〈E n 〉 ~ 4.5 MeV) with an intensity of ~5 × 106 n/s was used to irradiate the samples under study. A scintillation detector based on a BGO crystal was used to register the characteristic γ radiation from the inelastic fast neutron scattering and slow (thermal) neutron capture. This paper presents the results of humidity measurement in the range of 2–50% [1, 2].

The possibility of increasing the sensitivity of a neutron detector based on a TlInSe 2 crystal by introducing the 6 Li isotope into this crystal is investigated. Introduction of the isotope is conducted by the method of electrochemical intercalation from aqueous and nonaqueous solutions of LiCl and also from the melt of the LiCl–KCl eutectic. It is shown that intercalation by the electrochemical method from a LiCl solution in propylene carbonate, performed along the “c” axis of the crystal (along strong bond chains) is efficient. The attained concentration of introduced lithium amounts to (1–1.2) × 10 21 cm –3 , which increased the sensitivity of the detector by approximately four times. Good agreement between the calculated and experimental values of the detector sensitivity is demonstrated.

Исследовалась возможность увеличения чувствительности детектора нейтронов на основе полупроводника TlInSe2 путем введения в кристалл изотопа лития 6Li. Введение проводилось методом электрохимической интеркаляции из водных и неводных растворов LiCl, а также из расплава эвтектики LiCl-KCl. Показана эффективность интеркалирования электрохимическим методом из раствора LiCl в пропиленкарбонате, проводимого вдоль оси "с" кристалла (вдоль цепочек сильной связи). Достигнутая концентрация введенного лития составила (1-1.2)· 1021 см-3, что примерно вчетверо увеличило чувствительность детектора. Показано хорошее согласие между рассчитанным и фактическим значением чувствительности детектора. DOI: 10.21883/FTP.2017.06.44555.8170

We review the experimental results on the P -even and P -odd angular correlations of fission fragments in the fission of the 235 U and 239 Pu nuclei induced by unpolarized and polarized resonance neutrons, and on the TRI and ROT effects in the ternary and binary fission of actinides induced by polarized thermal neutrons. Also reported are the measured yields of prompt and delayed neutrons per fission event. The experimental data are analyzed within a novel theoretical framework developed by the JINR—RNC KI Collaboration, whereby the reduction of the multidimensional phase space of fission fragments to the JπK -channel space is consistently validated and the role of resonance interference in the observed correlation effects is revealed.

We performed an experimental search for the bound state singlet deuteron predicted in some microscopic calculations. The experiment consists in a high statistics measurement of gamma ray spectra after thermal neutron capture by hydrogen nuclei. The upper limit is obtained for the probability of the 3S1 - 1S0 -transition population of the deuteron singlet bound state with the bound energy in the interval 25-125 keV.

The possibilities of an isotope-indentifying study of layered structures in different regimes of a neutron wave field are considered. The detection of specularly reflected neutrons and secondary radiation (caused by neutron capture) in the form of charged particles, γ quanta, and nuclear fission fragments, as well as neutrons spin-flipped in a noncollinear magnetic field and on nuclei of elements with spin, makes it possible to implement isotope-indentifying neutron reflectometry.

The new cadmium and gadolinium-loaded polymethylmethacrylate based plastic scintillators with the mass fraction of the metals up to 2 % and 4 %, respectively, are described in this article. There are presented the techniques of the new materials preparation and their main properties: transmission spectra, light output and thermal neutrons detection efficiency. The light output of Cd-loaded scintillator with 2 % of metal is 67 % relative to the unloaded sample; the light output of Gd-loaded plastic scintillator with 4 % of the metal is reduced to 67.6 %. There is regular increase of the thermal neutrons detection efficiency for the both series of the scintillation materials.