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The history and current status of investigations of the unique two-step (n, γf) reaction observed in heavy nuclei under the influence of neutrons are discussed using the example of measurements made on the neutron time-of-flight spectrometer GNEIS in Gatchina. It is shown what is already known and what kind of information can be derived from experiments to study the (n, γf) reaction on resonance neutrons for the most important fissionable nuclei 235U and 239Pu, including information on the properties of primary gamma transitions between highly excited states near the neutron bonding energy.

Fragment angular distributions in heavy-nuclei fissions induced by neutrons with intermediate energies of 1–200 MeV are measured. Fragment-emission anisotropy W(0°)/W(90°) is studied as a function of incident-neutron energy. Results are consistent with those of other measurements using similar techniques, indicating that the reported measurements are free of significant systemic errors.

The measured angular distributions of fission fragments of 240Pu nuclei have been presented and theoretically analyzed. Measurements at energies above 10 MeV have been performed for the first time. A model description of the energy dependence of the angular anisotropy of fission fragments in the entire studied range of neutron energies has been proposed.

Problems of describing experimental data on the angular distributions of fragments of nuclear fission induced by intermediate-energy neutrons are discussed. A way of calculating angular distributions based on using the TALYS program is proposed. The capabilities of the technique for obtaining new information on the fission process and reactions at intermediate energies are shown by the example of describing data obtained for the $${}^{{237}}{\text{Np}}$$ nucleus.

Using the Geant4 software package, a numerical simulation of a neutron source of the time-offlight spectrometer GNEIS created on the basis of the SC-1000 synchrocyclotron with 1 GeV proton energy at the NRC Kurchatov Institute—PNPI (Gatchina) has been carried out. The influence of the structural features of the neutron source of the spectrometer on the spatial and energy distributions of neutrons has been studied. The intensity and spectral characteristics of the neutron flux in the range of 1–1000 MeV have been determined on the basis of the obtained information and detailed allowance for all elements of the neutron beam guide system. It is found that the best agreement between the experiment and calculation performed by means of Geant4 is observed when using the QGSP_INCLXX_HP model. In the neutron energy range of 1–200 MeV, the difference between the experimental and calculated shapes of the spectra is less than 25%.

The article presents a description of the ISNP/GNEIS testing facility with a neutron spectrum that reproduces the spectrum of atmospheric neutron radiation. The facility was developed at the Petersburg Nuclear Physics Institute (PNPI) of the National Research Center Kurchatov Institute in collaboration with the Institute of Space Device Engineering, a branch of JSC (Joint Stock Company) United Rocket and Space Corporation. The spallation neutron source of the facility is based on the 1-GeV SC-1000 proton synchrocyclotron at the PNPI. The internal neutron-production lead target produces 10-ns pulses of neutrons with a repetition rate of 45–50 Hz and an average neutron intensity of 3 × 1014 n/s (in the 4σ solid angle). In the irradiation area located at a distance of 36 m from the neutron source, a high-quality collimated neutron beam with a broad energy spectrum of 1–1000 MeV and a neutron flux of 4 × 105 n/(cm2 s) allows conducting accelerated single-event soft error testing of electronic components. In the course of the irradiation, the neutron energy spectrum and intensity and the spatial profile of the beam are controlled using a fission ionization chamber (beam monitor) and a position-sensitive multiwire proportional counter (beam profile meter). The data acquisition system of the ISNP/GNEIS facility utilizes 250 MS/s 12 bit CAEN waveform digitizers for the processing of signals from the monitor and profile meter by the neutron time-of-flight technique. In the report, parameters of the ISNP/GNEIS testing facility are discussed in comparison with analogous world-class facilities, as well as requirements and recommendations of the standards used in this field.

The experimental data on the angular distributions of fragments from the fission of 237Np nuclei induced by 1–200 MeV neutrons have been presented. Such measurements for neutron energies above 16 MeV have been performed for the first time. These distributions have been analyzed and the angular anisotropy in the center-of-mass of fragments has been determined in the entire energy range under study. A method involvng the complex dynamics of the formation and decay of highly excited nuclei and based on the TALYS program has been proposed to calculate the angular distributions of fission fragments in a wide energy range for the collision of nuclei with neutrons. It has been shown that the developed model describes well the main features of the energy dependence of the angular anisotropy for the 237Np target nuclei and can be used to extract new information on the reaction and fission process.

Experimental data on the angular distributions of 232Th, 233U, 235U, 238U, natPb, and 209Bi fission fragments in reactions induced by neutrons with intermediate energies of up to 200 MeV are presented. Measurements are made using the GNEIS time-of-flight (TOF) spectrometer with the neutron source based on the 1-GeV proton synchrocyclotron of the Petersburg Nuclear Physics Institute. Angular distributions and the anisotropy of fission fragments W(0°)/W(90°) calculated from these distributions are given together with the results of other authors. The disagreement between the results obtained in different works is discussed. The data presented in this work for the anisotropy of natPb and 209Bi fission fragments in reactions induced by neutrons with energies ranging from the fission threshold to 200 MeV are obtained for the first time.

In recent years, investigations of angular distributions of fragments in neutron-induced nuclear fission have been extended to intermediate energies, up to 200 MeV, as well as to a wide range of target isotopes. Using as an example the latest data obtained by our group for the reaction 237-Np(n,f), we discuss the specific features of fission fragment angular distribution and present a method for their simulation based on the code TALYS. It is shown that a simplified model reasonably describes energy dependence of the angular distribution in the whole range 1-200 MeV. The ways to improve the model are discussed along with the possibilities to use it for obtaining new information on fission and pre-equilibrium processes in neutron-nucleus interaction. We consider also the relevant problems of describing fission fragment angular distributions., Comment: 11 pages, 3 figures, Research was presented at the THEORY-5 Scientific Workshop on "Nuclear Fission Dynamics and the Emission of Prompt Neutrons and Gamma Rays", Castelvecchio Pascoli, Barga, Italy, September 24-26, 2019

The analysis of angular and energy distributions of prompt neutrons from the thermal neutron induced fission of 233U and 235U measured recently in the WWR-M research reactor (Gatchina, Russia) have been performed. The yield of “scission” neutrons has been estimated by comparing the measured distributions with calculations within the model of emission of neutrons from completely accelerated fragments. Besides taking into account “scission” neutrons, for the best description of measured angular and energy distributions of fission neutrons, the calculation should be performed under the assumption that neutrons with a higher (7-9%) probability are emitted along the fission axis in the center-of-mass system of fission fragments.

The angular distributions of fragments from the neutron-induced fission of natPb and 239Pu nuclei have been measured in the energy of range 1–200 MeV using the neutron time-of-flight spectrometer GNEIS. Fission fragments have been detected by position sensitive multiwire proportional counters. The results for the anisotropy of fission fragments deduced from the measured angular distributions have been presented. The results have been compared with the experimental data of other authors.

A brief description of the spallation pulsed neutron source and neutron TOF spectrometer GNEIS based on the 1 GeV proton synchrocyclotron of PNPI in Gatchina is presented. The main parameters of the GNEIS are given in comparison with the analogous world-class facilities. The experimental capabilities of the GNEIS are demonstrated by the examples of some nuclear physics and applied research experiments carried out during four decades of its operation.

The study investigates the language difficulties of the Linguistic Landscape (LL) optimization for the establishment of a convenient system of navigation for foreign tourists in Russian Federation. The authors discuss the approaches to translating Russian urbanonyms into the English language. Particular attention is paid to existing evaluation guidelines for the translation of urbanonyms. The study reveals a systemic approach in translation as well as errors and inconsistent practical implications resulted in Linguistic Landscape of different cities. The results on the analysis of the translated urbanonyms implemented during the preparation for 2018 FIFA World Cup Russia (Ekaterinburg) are reported to give the evaluation of weaker and stronger translations in terms of unimpeded communication. Of special importance are difficult cases of translation where the authors suggest alternative solutions.

New results of the neutron-induced fission experiments carried out at the neutron time-of-flight spectrometer GNEIS of the PNPI are given. Angular distributions of fission fragments from the neutron-induced fission of 233U and 209Bi nuclei have been measured in the energy range 1–200 MeV using position sensitive multiwire proportional counters as fission fragment detector. The recent improvements of the measurement and data processing procedures are described. The data on anisotropy of fission fragments deduced from the measured angular distributions are presented in comparison with the experimental data of other authors.

A description of the testing facility ISNP with spectrum resembling that of terrestrial neutron radiation developed at the PNPI (Gatchina) is given. A broad spectrum (1–1000 MeV) spallation neutron source of the facility with a neutron flux of $4 \cdot {10^5}\;\text{n}/(\text{cm}^2{\cdot}\text{s})$ is used for accelerated soft error testing. High-quality collimation of the neutron beam in conjunction with the TOF-technique enables to carry out precise and reliable monitoring of the neutron beam. The results of recent tests carried out at the ISNP by the Branch of JSC “URSC” - “ISDE” (Moscow) are presented.

The energy spectrum of prompt neutrons emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) “Evaluation of Prompt Fission Neutron Spectra of Actinides”was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei. The following technical areas were addressed: (i) experiments and uncertainty quantification (UQ): New data for neutron-induced fission of 233U, 235U, 238U, and 239Pu have been measured, and older data have been compiled and reassessed. There is evidence from the experimental work of this CRP that a very small percentage of neutrons emitted in fission are actually scission neutrons; (ii) modeling: The Los Alamos model (LAM) continues to be the workhorse for PFNS evaluations. Monte Carlo models have been developed that describe the fission phenomena microscopically, but further development is needed to produce PFNS evaluations meeting the uncertainty targets; (iii) evaluation methodologies: PFNS evaluations rely on the use of the least-squares techniques for merging experimental and model data. Considerable insight was achieved on how to deal with the problem of too small uncertainties in PFNS evaluations. The importance of considering that all experimental PFNS datamore » are “shape” data was stressed; (iv) PFNS evaluations: New evaluations, including covariance data, were generated for major actinides including 1) non-model GMA evaluations of the 235U(nth,f), 239Pu(nth,f), and 233U(nth,f) PFNS based exclusively on experimental data (0.02 ≤ E ≤ 10 MeV), which resulted in PFNS average energies E of 2.00±0.01, 2.073±0.010, and 2.030±0.013 MeV, respectively; 2) LAM evaluations of neutron-induced fission spectra on uranium and plutonium targets with improved UQ for incident energies from thermal up to 30 MeV; and 3) Point-by-Point calculations for 232Th, 234U and 237Np targets; and (v) data testing: Spectrum averaged cross sections (SACS) calculated for the evaluated 235U(nth,f) PFN field agree within uncertainties with evaluated SACS experimental data. Despite the observed reduction of the PFNS E by about 30 keV for neutron-induced fission of 233U, 235U, and 239Pu, the criticality benchmark outcomes suggested that new evaluations can achieve the same (or better) integral performance with respect to existing evaluations, but the strong compensating effects observed need to be addressed. Summarizing, this project has significantly improved PFNS evaluations and evaluation methodology, provided new PFNS data for applications, and also highlighted the areas for future research« less

This article summarizes the results of pre-design studies to reduce pollutant emissions of gas turbine compressor packages. The amount of pollutant emissions of compressor packages used at the Ukrainian gas transmission system as well as gas turbines manufactured by Ukrainian companies is presented. The main methods for reduction in pollutant emissions of gas turbines were analyzed. It was shown that one of the promising methods is to use special catalyst systems in the exhaust ducts. To select the catalyst location, a series of numerical simulations have been performed in the exhaust system of gas turbine compressor package GPA-C-16S type. It was shown that flow in the exhaust system has a complex structure mostly caused by features of the flow at the exhaust collector outlet. It was also found that swirling of the flow at the turbine outlet causes significant change of the flow at the exhaust system (18 % of the mass flow of exhaust gas moves along one of the wall and 82 % along another one). To prevent the degradation of the flow because of swirling at the turbine outlet the especially designed tongue was used at the exhaust collector. To reduce the overall non-uniformity of the flow the exhaust duct design with tubular straightener has been developed.To produce utility heat compressor packages of GPA-C-16S type can be equipped with heat recovery units, of between 3.5 to 9 MW. Their application allows achievement of thermal efficiencies of 0.36 to 0.46. The heat recovery units can contain several separate heat exchangers. Heat power control of the heat recovery units is carried out by heat exchangers on-off and by controlling the flow rate of exhaust gases through them. The design of the heat recovery units allows filling heat exchangers with water without shut-down of the gas turbine. To avoid high thermal stresses heat exchangers are cooled with atmospheric air supplied by fan of the heat recovery unit cooling system., This article summarizes the results of pre-design studies to reduce pollutant emissions of gas turbine compressor packages. The amount of pollutant emissions of compressor packages used at the Ukrainian gas transmission system as well as gas turbines manufactured by Ukrainian companies is presented. The main methods for reduction in pollutant emissions of gas turbines were analyzed. It was shown that one of the promising methods is to use special catalyst systems in the exhaust ducts. To select the catalyst location, a series of numerical simulations have been performed in the exhaust system of gas turbine compressor package GPA-C-16S type. It was shown that flow in the exhaust system has a complex structure mostly caused by features of the flow at the exhaust collector outlet. It was also found that swirling of the flow at the turbine outlet causes significant change of the flow at the exhaust system (18 % of the mass flow of exhaust gas moves along one of the wall and 82 % along another one). To prevent the degradation of the flow because of swirling at the turbine outlet the especially designed tongue was used at the exhaust collector. To reduce the overall non-uniformity of the flow the exhaust duct design with tubular straightener has been developed. To produce utility heat compressor packages of GPA-C-16S type can be equipped with heat recovery units, of between 3.5 to 9 MW. Their application allows achievement of thermal efficiencies of 0.36 to 0.46. The heat recovery units can contain several separate heat exchangers. Heat power control of the heat recovery units is carried out by heat exchangers on-off and by controlling the flow rate of exhaust gases through them. The design of the heat recovery units allows filling heat exchangers with water without shut-down of the gas turbine. To avoid high thermal stresses heat exchangers are cooled with atmospheric air supplied by fan of the heat recovery unit cooling system.

Angular distributions of fission fragments from the neutron-induced fission of 232Th, 235U, and 238U have been measured in the energy range 1–200 MeV at the neutron time-of-flight (TOF) spectrometer GNEIS using position sensitive multiwire proportional counters as fission fragment detector. A short description of the experimental equipment and measurement procedure is given. The anisotropy of fission fragments deduced from the data on measured angular distributions is presented in comparison with experimental data of other authors.

Angular distributions of fission fragments from the neutron-induced fission of 232 Th, 233 U, 235 U, 238 U and 209 Bi have been measured in the energy range 1–200 MeV at the neutron TOF spectrometer GNEIS based on the spallation neutron source at 1 GeV proton synchrocyclotron of the PNPI (Gatchina, Russia). The multiwire proportional counters have been used as a position sensitive fission fragment detector. A description of the experimental equipment and measurement procedure is given. The anisotropy of fission fragments deduced from the data on measured angular distributions is presented in comparison with experimental data of other authors, first of all, the recent data from WNR at LANSCE (Los Alamos, USA) and n_TOF(CERN).

Questions of influence of average interval, accuracy of application of intervals between shoots and field germination of seeds on relative harvest are considered. The depen-dences of the relative yield of sugar beet from the average interval between shoots, the coefficient of variation of the interval between shoots with the influence of field germination are got. These dependencies are installed with process simulation of flow transformation of seeds obtained from the sowing, in the flow of plants and then calculating the relative yields. The basis of the simulation is mathematical, logical and experimental data, so the results are close to the actual ones.

The main results of studying the properties of “instantaneous” neutrons and γ photons during the fission of 233, 235U(nth, f) and 239Pu(nth, f) nuclei and spontaneous fission of 252Cf, which were performed on the WWR-M reactor at the St. Petersburg Nuclear Physics Institute, Russian Academy of Sciences, are presented. Along with obtaining the main characteristics of the instantaneous radiation from fission fragments, these studies were also aimed at gaining deeper insight into such exotic processes as the emission of break neutrons and γ photons from a fissioning nucleus near the break point. These investigations were performed on different experimental setups using different analytical methods. This approach allowed us not only to find but also to reduce to minimum possible systematic effects. The yields of break neutrons were found to be about (5–7) × 10−2 of the total number of neutrons per 233, 235U(n, f) fission event and approximately twice as much for 239Pu(n, f) and 252Cf. The coefficient of T-odd asymmetry for γ photons is in agreement with the estimate obtained on the assumption that the observed effect is mainly related to the γ photons emitted by excited fragments with highly oriented angular momenta. This fact gave grounds to conclude that the desired break γ photons cannot be reliably selected (within the obtained experimental accuracy) against the much larger background of γ photons from fission fragments.

A neutron beam with an energy spectrum resembling that of atmospheric neutron radiation has been developed at the 1000-MeV synchrocyclotron of the Petersburg Nuclear Physics Institute. The beam is intended for testing the radiation resistance of electronics and meets the requirements of the JEDEC international standard. The only test facility in which the neutron spectrum is close to the standard in the energy range of 0.1–750 MeV has been developed at the Los Alamos National Laboratory on the basis the LAMPF linear proton accelerator and used by aviation and space companies of the United States, Europe, and Asia to test their electronic equipment. In contrast to the test facilities in Los Alamos and Uppsala (Sweden), the method of neutron production on an internal accelerator target is used by the Petersburg Nuclear Physics Institute. The development of the neutron beam and the test facility extends considerably the experimental potential of radiation research and can act as a basis for establishing a unique center for radiation tests of aviation and space electronic equipment in compliance with the requirements of international standards.

Nowadays, there is an increased interest in a complete study of the neutron-induced fission of 237Np. This is due to the need of accurate and reliable nuclear data for nuclear science and technology. 237Np is generated (and accumulated) in the nuclear reactor core during reactor operation. As one of the most abundant long-lived isotopes in spent fuel (“waste”), the incineration of 237Np becomes an important issue. One scenario for burning of 237Np and other radio-toxic minor actinides suggests they are to be mixed into the fuel of future fast-neutron reactors, employing the so-called transmutation and partitioning technology. For testing present fission models, which are at the basis of new generation nuclear reactor developments, highly accurate and detailed neutron-induced nuclear reaction data is needed. However, the EXFOR nuclear database for 237Np on neutron-induced capture cross-section, σγ, and fission cross-section, σf, as well as on the characteristics of capture and fission resonance parameters (Γγ, Γf, σoΓf, fragments mass-energy yield distributions, multiplicities of neutrons vn and γ-rays vγ), has not been updated for decades.

To estimate the main characteristics of neutrons emitted shortly before the scission of a fissioning nucleus, various experiments sensitive to the presence of these scission neutrons in thermal-neutron-induced fission of 235U and spontaneous fission of 252Cf were performed. The results of the experiments were analyzed within theoretical calculations allowing for various possible neutron-emission mechanisms, including the possibility of the emergence of neutrons from the scission of a nucleus.

The neutron capture cross section of 237 Np has been measured relative to the 10B (n, α)7Li* cross section by the time-of-flight method in the energy range from 0.02 to 100 eV. The 46 MeV electron linear accelerator at the Research Reactor Institute, Kyoto University, was used as a pulsed neutron source. The BGO scintillation detector was employed in conjunction with the flash ADC-based data taking system for measurement and data accumulation. For the first time the capture cross section of 237 Np in resonance energy range was measured using the total energy gamma-ray detector. The results of present measurements have been compared with the evaluated capture cross sections of ENDF/B-VI and JENDL-3.3, as well as with the data measured by other authors.

During the last several years, the measurements of neutron-induced fission cross-sections of actinides and stable isotopes have been performed at the GNEIS facility. At present moment, the new series of experiments for measurements of fission cross-section ratios relative to 235 U have been began for 240 Pu, 243 Am and nat W in a wide energy range of incident neutrons from 1 MeV to 200 MeV. The measurements were performed using the multiplate ionization chamber and time-of-flight technique. The first results of this measurement in case of 240 Pu and 243 Am are presented in comparison with the other data.

The description of an experimental set-up for neutron multiplicity measurements and its specific data processing procedures are presented together with some results for 252 Cf ( sf ) . With this experimental set-up the light and heavy fission fragment kinetic energies for every fission event can be registered simultaneously with the number of prompt neutrons emitted by each of the complementary fission fragments. The proposed data processing makes it possible to perform the reconstruction of pre-neutron fission fragment masses and kinetic energies as well as the initial neutron multiplicity distribution.

A 16-section BGO scintillation detector having a total volume of 8.54 l and an associated 40 MHz flash-ADC-based data taking system were developed. This detector system is intended for measurements of neutron capture cross-sections of radioactive nuclei by the time-of-flight method. The detector response function and efficiency, gamma-ray and neutron energy resolution, and backgrounds were evaluated experimentally and by calculation. Neutron capture cross-section measurements with 10 B , 197 Au and 237 Np samples were carried out in the energy range of 1– 1000 eV to demonstrate the performance of the system.

In order to develop a neutron flux monitor for long-term neutron irradiation, the thermal neutron(2,200 m/s neutron) capture cross section (≤σ0) and the resonance integral (I 0)of the 109Ag(n,γ)110mAg reaction were measured by the activation and γ-ray spectroscopic methods. Silver foils were irradiated with and without a Cd shield capsule at the Rikkyo Research Reactor. The Co/A1 and Au/A1 alloy wires were irradiated together with silver foils in order to monitor the thermal neutron flux and the fraction of the epi-thermal neutron part (Westcott's index). A high purity Ge detector was used for the γ-ray measurements of the irradiated samples. The σ0 and the I 0 of the 109Ag(n,γ)110mAg reaction are 4.12±0.10 b and 67.9±3.1 b, respectively. The σ0 is 12% smaller than the tabulated one (4.7±0.2 b). On the other hand, the I 0 is in agreement with the tabulated one (72.3±4.0 b) within the limits of error.

Fission cross section ratios of 233U, 238U, 232Th, 239Pu, 237Np, natural Pb and 209Bi to 235U have been measured in a wide energy range of incident neutrons from 1 MeV to 200 MeV using a time-of-flight technique at the neutron spectrometer GNEIS based on the 1-GeV proton synchrocyclotron of PNPI. For actinide targets, the threshold cross section method and evaluated data below 14 MeV were used for normalization of the shape measurement data, while the evaluated and recommended fission cross sections of 235U were used to convert the ratio data to absolute fission cross sections. For Pb and Bi targets, an absolute normalization of the measured cross section ratios has been done using the thickness of the targets and detection efficiencies.

The description of an experimental set-up for the study of the excitation energy distribution of fission fragments by means of coincident measurement of fission neutrons is presented. For every fission event the kinetic energy and mass of both fragments are registered simultaneously with the number of prompt neutrons emitted by each of the complementary fission fragments. With this set-up, the fission fragments are detected by a twin ionization chamber and the neutrons - by two large Gd-loaded liquid scintillator tanks.

The number of prompt neutrons emitted in the fission event have been measured separately for each complementary fragment in coincidence with fragment mass and kinetic energies in spontaneous fission of 252Cf, 244Cm and 248Cm. Two high efficient Gd-loaded liquid scintillator tanks were used for the neutron registration. Approximately 3 106 fission events coincident with prompt neutron emission have been accumulated for each isotope. The mean neutron multiplicity, the dispersion and the covariance of the multiplicity distributions have been obtained as a function of fission fragment mass and kinetic energy. The neutron multiplicity data have been corrected for neutron registration efficiency, background and pile-up. Dependencies of the moments of the multiplicity distributions on the fragment mass and total kinetic energy for different mass bins, as well as mass and total kinetic energy distributions of the fission fragments are presented, discussed and compared for the different isotopes investigated. The ...

The Pade approximations of the Doppler broadening function ψ(θ, x) have been used for the calculations of resonance self-shielding factors used in activation measurements. It is shown that this method of the calculations is effective from the point of view of fastness and accuracy.

A description of the proton (IS SC-1000, IS OP-1000) and neutron (IS NP/GNEIS) test facilities at the 1 GeV synchrocyclotron SC-1000 of the PNPI used for radiation resistance testing of electronic components and systems intended for avionic and space research is presented. A unique conjunction of proton beams with variable energy 100–1000 MeV and atmospheric like neutron beam with broad energy range (1–1000 MeV) spectrum enables to perform complex testing of the semiconductor electronic devices within a single testing cycle.

The neutron capture cross section of 237Np has been measured relative to the 10B(n,α)7Li* cross section in the energy range from 0.02 to 100 eV. The measurements were carried out by the time‐of‐flight method using the 8.54‐liter BGO scintillator as a 4π capture gamma‐ray detector and the 46‐MeV Linac as a pulsed neutron source. The results of present measurements have been compared with experimental data of other authors and evaluated data.

A method of thermal neutron‐capture cross‐section measurement by using a pair spectrometer and unfolding prompt gamma‐ray spectra is described. To evaluate the validity of the method, it was applied for the measurement of the thermal neutron cross section of 14N. A pair spectrometer system was used to measure prompt gamma rays emitted from 15N produced by thermal neutron capture. Response functions of the system were calculated by using EGS‐4 code. To verify the reproducibility of the response functions, the measured spectrum of prompt gamma rays of 15N was reproduced by using EGS‐4 code, which was used for calculating response functions.

The neutron‐induced fission cross‐section ratios relative to 235U has been measured for 240Pu, 243Am and natW in a wide energy range of incident neutrons from 1 MeV to 200 MeV at the GNEIS facility. The measurements were performed using the multiplate ionization chambers and time‐of‐flight techniques. The results obtained in this measurement are presented in comparison with the other data.

Neutrons emitted in fission events were measured separately for each complementary fragment in correlation with fission fragment energies. Two high‐efficiency Gd‐loaded liquid scintillator tanks were used for neutron registration. Fission fragment energies were measured using a twin Frisch gridded ionization chamber with a pinhole collimator. The neutron multiplicity distributions were obtained for each value of the fission fragment mass and energy and corrected for neutron registration efficiency, background, and pile‐up. The dependency of these distributions on fragment mass and energy for different energy and mass bins as well as mass and energy distribution of fission fragments are presented and discussed.

A new method to obtain information about the properties of low energy p-resonances in heavy fissile nuclei is described. It is based on a study of neutron energy dependence of the forward-backward asymmetry of angular distribution of fission. fragments. which is the result of s- and p-wave interference in neutron capture. The investigations of this effect for U-235 have been carried out using the neutron TOF-spectrometer GNEIS in Gatchina. The irregular energy behavior of the asymmetry coefficient α nf fb was observed in accordance with theory predictions. For some strong p-resonances the positions and effective widths have been determined at first.

The neutron total cross sections are measured with an accuracy △σ/σ ∼ 10−3 for Bi and Si in energy range from 1 eV to 100 eV and for 208Pb and C in the range from 1 eV to 10 keV using the time-off-light facility GNEIS in Gatchina. An estimated value of the neutron electric polarizability is αn=(2.6±1.4)·10−3 fm3.