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Tagged neutrons are used to perform an experimental investigation of the inelastic scattering of 14.1 MeV neutrons on 23Na and 35Cl nuclei as part of the TANGRA project at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research. The energies and yields of γ quanta for transitions observed in the experiment are measured, and the γ angular distribution coefficients for the highest intensity γ transitions are obtained. The experimental data are compared to others in the literature.

The TALYS 1.9 program is used to calculate cross sections of processes that occur during the scattering of fast neutrons on 48Ti, 52Cr, and 56Fe 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 inelastic scattering of 14.1 MeV neutrons off magnesium nuclei is studied at the TANGRA facility using tagged neutrons and an ING-27 standard neutron generator. The energies and partial cross sections of visible γ transitions induced in different reactions between neutrons and magnesium nuclei are determined. The measured angular distribution of γ quanta for 24Mg is analyzed and compared to results from other experimental studies.

An investigation of inelastic scattering of 14.1 MeV neutrons on an iron sample was carried out using an improved TANGRA (TAgged Neutron and Gamma RAys) setup at JINR (Dubna). The yields of the occurring $$\gamma $$ -transitions and anisotropy of the emitted $$\gamma $$ -rays were measured using the tagged neutron method. The setup with a high-purity germanium (HPGe) detector was used to obtain the energy spectrum of $$\gamma $$ -rays. The setup with 18 BGO scintillation detectors positioned in a circle around the sample was used to obtain angular distributions of $$\gamma $$ -rays. A detailed $$\gamma $$ -spectrum for $$(n,X\gamma )$$ reactions was obtained and the $$\gamma $$ -ray angular distribution was measured for the 847 keV and 1238 keV $$\gamma $$ -transitions. The distribution was fitted by Legendre polynomials up to fourth order and the angular distribution coefficients $$a_2$$ , $$a_4$$ were extracted. A comparison with other published experimental results is given. Model calculations using computer code TALYS 1.9 were performed. The results of calculations are discussed in comparison with the obtained experimental data.

The work is devoted to measuring the angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by 12C nuclei. A portable ING-27 neutron generator (designed and fabricated at VNIIA, Moscow) with a built-in 64-pixel silicon α-detector was used as a source of tagged neutrons. The γ-rays of characteristic nuclear radiation from 12C were detected with a spectrometric system that consisted of 22 γ-detectors based on NaI(Tl) crystals arranged around the carbon target. The measured angular distribution of 4.43-MeV γ-rays is analyzed and compared with the results of other published experimental works.

For investigation of the basic characteristics of 14.1 MeV neutron induced nuclear reactions on a number of important isotopes for nuclear science and engineering, a new experimental setup TANGRA has been constructed at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research in Dubna. For testing its performance, the angular distribution of γ-rays (and neutrons) from the inelastic scattering of 14.1 MeV neutrons on high-purity carbon was measured and the angular anisotropy of γ-rays from the reaction 12 C(n, n′ γ)12 C was determined. This reaction is important from fundamental (differential cross-sections) and practical (non-destructive elemental analysis of materials containing carbon) point of view. The preliminary results for the anisotropy of the γ-ray emission from the inelastic scattering of 14.1- MeV neutrons on carbon are compared with already published literature data. A detailed data analysis for determining the correlations between inelastic scattered neutron and γ-ray emission will be published elsewhere.

The characteristics of the setup for analyzing the elemental composition of organic substances using spectroscopy of γ rays induced by tagged neutrons with an energy of ∼14 MeV in an inelastic neutron scattering reaction are discussed. An ING-27 D-T neutron generator with a built-in position-sensitive α detector, fast neutron and γ detectors, and a multichannel detecting system providing a subnanosecond time resolution are parts of the experimental setup. The correlation between the exit angle of a neutron and the number of the α pixel, as well as the anisotropy in emission of γ rays in the inelastic neutron scattering reaction, are measured, and the errors of these measurements are estimated.

A tagged neutron technology for remote neutron monitoring is used to reduce the background counting rate in recording of useful events. The key elements of the technology are a neutron generator with a built-in α-particle detector, nanosecond electronic system, and fast detectors of secondary radiation produced by emitted neutrons. A module for monitoring and measuring the pulse-height and time parameters of the secondary radiation detector with a time reference to the α-particle detector is described. A prototype of the experimental setup comprising the main components of a standard system based on the tagged neutron technology has been designed to test the module. Numerical calculations have been performed to simulate the γ-ray and neutron transport and the event recording procedure as applied to the geometry of the experimental setup. The time errors and the main sources of background events in measurements using the tagged neutron technology have been investigated. Background counts are shown to affect only slightly the useful data acquired in this geometry.

A neutron generator developed for instrumentation for pulsed neutron logging of oil and gas wells is described in the paper. The generator consists of a power supply, a switching unit, and acceleration tubes placed coaxially on a common chassis in a 42 mm diameter housing. Laboratory and field testing of the generator is very briefly summarized. The small diameter, high neutron flux per pulse, and operating life make the generator suitable for use in experimental neutron physics, investigating nuclear reactors, thermonuclear installation neutron field monitoring, and neutron-activation analysis of elemental material composition. 4 refs., 4 figs.

Nowadays in Russia and abroad there are several groups of scientists, engaged in development of systems based on “tagged” neutron method (API method) and intended for detection of dangerous materials, including high explosives (HE). Particular attention is paid to possibility of detection of dangerous objects inside a sea cargo container. Energy gamma‐spectrum, registered from object under inspection is used for determination of oxygen/carbon and nitrogen/carbon chemical ratios, according to which dangerous object is distinguished from not dangerous one. Material of filled container, however, gives rise to additional effects of rescattering and moderation of 14 MeV primary neutrons of generator, attenuation of secondary gamma‐radiation from reactions of inelastic neutron scattering on objects under inspection. These effects lead to distortion of energy gamma‐response from examined object and therefore prevent correct recognition of chemical ratios. These difficulties are taken into account in analytical method, presented in the paper. Method has been validated against experimental data, obtained by the system for HE detection in sea cargo, based on API method and developed in VNIIA. Influence of shielding materials on results of HE detection and identification is considered. Wood and iron were used as shielding materials. Results of method application for analysis of experimental data on HE simulator measurement (tetryl, trotyl, hexogen) are presented.

New methods of non-destructive control must be developed and existing ones must be improved in order to solve the problem of control of fissile materials (FMs) in vessels with nuclear wastes, and to provide safe operation of nuclear power plants. This paper considers the application of active methods of control on the basis of DD or DT pulsed neutron generators. These methods are more comprehensive and sensitive than traditional passive methods for detection of neutron and gamma radiation from nuclear materials, such as U-235 and Pu-239. As a particular method for FM control we use a technique of differential die-away of neutrons, detected by He-3 proportional counters. Calculations performed for 60 litres containers showed the high sensitivity of detection of induced fission neutrons (up to 10 mg of U-235) in a graphite matrix and much lower sensitivity of detection for a container with an iron matrix.