Neutron Resonance Capture Analysis (NRCA) is presently being developed at the Frank Laboratory of Neutron Physics (FLNP) to determine the elemental composition of samples. The NRCA is a nondestructive method that allows measuring objects’ bulk composition. The procedure is based on detecting neutron resonances in radiative capture and the measurement of the yield of reaction products in these resonances. The experiments are carried out at the Intense REsonance Neutron source (IREN). In this study, we applied the NRCA to investigate an archaeological object provided by the Museum and Exhibition Complex (MVK) "Volokolamsk Kremlin". The object was a women’s Old Believer cross (second half of the 17th century) found in the Moscow region, Volokolamsk district, the village of Chubarovo.

Investigation of spatial parity in reactions of polarized neutrons with light nuclei is an important topic in the framework of exploring the fundamental problem of understanding the manifestation of the weak interaction in nuclear reactions and for estimating the parameters of the weak nucleon–nucleon interaction. In this paper, the ongoing experimental program of highly sensitive and high-precision measurements of P‑odd asymmetries in the reactions of polarized thermal and cold neutrons with lithium and boron nuclei is reviewed. Within this program, the coefficients of P-odd asymmetry of reaction products in the reactions induced by cold- and thermal-neutrons on the isotopes of light nuclei 6Li and 10B were measured with record-high sensitivity ~10–8 as $$\alpha _{{P{\text{ - odd}}}}^{{^{{\text{6}}}{\text{Li}}{\text{,exp}}}} = - (8.8 \pm 2.1) \times {{10}^{{ - 8}}}$$ , $$\alpha _{{P{\text{ - odd}}}}^{{^{{10}}{\text{B}},\gamma ,\exp }} = (0.0 \pm {{2.6}_{{{\text{stat}}.}}} \pm {{1.1}_{{{\text{syst}}{\text{.}}}}}) \times {{10}^{{ - 8}}},$$ and $$\alpha _{{P{\text{ - odd}}}}^{{{{\alpha }_{0}} + {{\alpha }_{1}}{{,}^{{10}}}B,\exp }} = - (11.2 \pm 3.4) \times {{10}^{{ - 8}}}$$ . For the first time ever, nonzero values were obtained for two of these asymmetries. Our data for tritium emission in the $$^{6}{\text{Li(}}n,a{{)}^{3}}{\text{H}}$$ reaction and γ emission in the $$^{{10}}{\text{B}}{{(n,a)}^{{74}}}{\text{Li}}^{*} \to \gamma \to {{\,}^{7}}{\kern 1pt} {\text{Li(gr}}{\text{.st}}{\text{.)}}$$ reaction agree with those of other experiments when interpreted within the cluster model, but rule out the so-called “best DDH values” of weak-interaction coupling constants. Interpreting the data on these reactions relying on “first principles” only would be highly desirable.

Abstract—Neutron Resonance Capture Analysis (NRCA) is currently being developed in the Frank Laboratory of Neutron Physics (FLNP) for the purpose of determining the element composition of samples. This method is based on registering neutron resonances in radiative capture and measuring the yield of reaction products in these resonances. To test the capabilities of this method, such investigations have been carried out in collaboration with the Institute of Archaeology of the Russian Academy of Sciences at the IREN pulsed neutron source, FLNP, for ancient coins from Phanagorian treasure. A cylindrical multisectional liquid scintillator detector is used to detect γ-quanta.

The temporal characteristics of a time-of-flight spectrometer installed on the first channel of the IBR-2 reactor are investigated. A change in the flash time of the reactor relative to the start depending on the measurement time from the beginning of the reactor operation cycle is discovered. The neutron deceleration time is measured as a function of the neutron wavelength. A dependence of the half-width of the reflections on the neutron wavelength is established. The measurements are carried out in a wide range of Bragg angles from 0.0567232 to 0.34180977 rad (from ~3° to ~19°). An estimate is made for the mosaic pattern of a single crystal.

A new method of measuring neutron lifetimes on pulsed neutron sources based on changes in the neutron spectrum during the time of the neutron transit along a rather large path length due to their decay is proposed. The main advantage of this method is the use of relative measurements. Simulating the experiment made it possible to explore the influence of background and neutron losses caused by both the interaction with residual gas and the different level of detector efficiency on the systematic errors. All parameters can be measured experimentally.

At the JINR Laboratory of Nuclear Physics, neutron–nucleus interactions are investigated for fundamental and applied purposes using the IREN pulsed neutron source. The applied research includes an elemental analysis of constituent materials of various devices. This paper describes the elemental-analysis techniques employed and reports the measurement of palladium abundances in the engine components of the Proton rocket carrier. The elemental-analysis technique involving resonance neutrons, currently implemented with the Romashka apparatus, is shown to be sensitive to palladium abundances at a level of 2 mg/g for samples with masses on the order of 60 g. Further developing the method will boost its sensitivity and allow for elemental analyses of larger samples and their assemblies.

We present measurements of P-odd asymmetry of emission of a-particles in the 10B(n, alpha)(7) Li nuclear reaction, which are carried out using beams of polarized cold neutrons at Petersburg Nuclear Physics Institute (PNPI, Gatchina, Russia) and Institut Max von Laue-Paul Langevin (ILL, Grenoble, France) nuclear reactors. The alpha-particle detector is an ionization chamber with insensitive gaseous layer. We measured the P-odd asymmetry coefficient to be equal to alpha(p-odd) (10 beta,alpha) = -(11.2 +/- 3.4).10(-8). (C) 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license.

We present measurements of P-odd asymmetry of emission of α-particles in the B10(n,α)Li7 nuclear reaction, which are carried out using beams of polarized cold neutrons at Petersburg Nuclear Physics Institute (PNPI, Gatchina, Russia) and Institut Max von Laue – Paul Langevin (ILL, Grenoble, France) nuclear reactors. The α-particle detector is an ionization chamber with insensitive gaseous layer. We measured the P-odd asymmetry coefficient to be equal to αP-oddB10,α=−(11.2±3.4)⋅10−8.

26 March 2016 marked 60 years since the Joint Institute for Nuclear Research was founded in 1956 and within which the Laboratory of Neutron Physics was established. Already four years later, in 1960, the world's first pulsed fast reactor (known by its Russian acronym as IBR) operating in the periodic mode was put into operation, followed in 1984 by IBR-2. The research achievements over the last decade are summarized, the state-of-the-art laboratory hardware is discussed, and the prospects for the future are reviewed.

The paper presents results of preliminarymeasurements of the left–right asymmetry in integral spectra of γ-quanta emitted in the interaction of polarized thermal neutrons with nuclei. These results indicate that for all cases of measured statistically significant P-odd asymmetry, the left–right asymmetry coefficient is much smaller than the P-odd asymmetry coefficient. This observation is not consistent with the predictions of theoretical calculations.

One of the applications of neutron spectroscopy for applied purposes is a nondestructive determination of the isotopic composition of samples under study. The method is based on the registration of neutron resonances and the measurement of the yield of reaction products in the resonances. The resonance energies are known practically for all stable nuclei and the set of energies does not coincide completely for any pair of isotopes. It allows determining the isotope composition. These measurements have been performed for a number of targets at the IREN Facility.

For incident neutrons with energy about few MeV there are not so many cross section experimental data and between existing data there are differences from one group to another. For fast neutrons many channels are open and the cross sections usually are small (order of tens or hundred of milibarns) and their measurements are difficult and affected by high background. On the other hand in this incident neutrons energy region the mechanism of nuclear reaction is passing from compound to pre-equilibrium and direct processes. In this work the cross sections for nuclear reactions induced by fast neutrons and emission of charged particles using the computer code Talys were evaluated and they are compared with experimental data obtained mainly at FLNP JINR. The theoretical and experimental cross section values obtained for nuclei as Sm, Zn, Nd and other nuclei can be used in many fields of sciences and one of great interest nowadays is the nuclear astrophysics for rates calculations.

The new experimental setup TANGRA (Tagged Neutrons & Gamma Rays), for the investigation of neutron induced nuclear reactions, e.g. (n,xn’), (n,xn’γ), (n,γ), (n,f), on a number of important isotopes for nuclear science and engineering (235,238U, 237Np, 239Pu, 244,245,248Cm) is under construction and being tested at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in Dubna.The TANGRA setup consists of: a portable neutron generator ING-27, with a 64-pixel Si charge-particle detector incorporated into its vacuum chamber for registering of α-particles formed in the T(d, n)4He reaction, as a source of 14.1 MeV steady-state neutrons radiation with an intensity of ∼5x107n/s; a combined iron (Fe), borated polyethylene (BPE) and lead (Pb) compact shielding-collimator; a reconfigurable multi-detector (neutron plus gamma ray detecting system); a fast computer with 2 (x16 channels) PCI-E 100 MHz ADC cards for data acquisition and hard disk storage; Linux ROOT data acquisition, visualization and analysis software. The signals from the α-particle detector are used to ‘tag’ the neutrons with the coincident α-particles. Counting the coincidences between the α-particle and the reaction-product detectors in a 20ns time-interval improves the effect/background-ratio by a factor of ∼200 as well as the accuracy in the neutron flux determination, which decreases noticeably the overall experimental data uncertainty.

The P-odd effect in the radiation cross section of capture of longitudinally polarized neutrons in a sample of natural lead is measured. The experiment was performed at PF1B facility at the Institut Max von Laue-Paul Langevin. The neutron polarization P n was 92%, the total flux of polarized neutrons was ∼3 × 1010 n/s, and the mean neutron wavelength was λ = 4.7 Å. Taking into account “0-test” we estimated the asymmetry: a γ(natPb) = (2.3 ± 3.5) × 10−7, i.e., α γ ≤ 8.1 × 10−7 at 90% confidence level.

The nuclear-physical characteristics obtained for a gallium target in a series of experiments using the time-of-flight method, the method of threshold indicators and a spectrometer based on a 3He proportional counter on the IREN setup (JINR, Dubna) are presented. The absolute values of the energy spectra of leakage neutrons in the energy range from 10 keV to 15 MeV were measured. The activation method was used to measure the neutron flux density on the surface of a gallium target: (2.882 ± 0.098) · 108 sec–1 · cm–2. The integral yield of neutrons obtained from the gallium target on the basis of these data was 1.54 · 1014 sec–1 with average current 4 mA. The time dependence of the activation level of the gallium target was measured. It was shown as a result of the analysis that the background level is reached on the surface of the irradiated gallium target in 5 days.

Parity violation effects (PV) in nuclear reaction were discovered in the 60 years of the last century in the capture of thermal transversal polarized neutrons by 113Cd nucleus. In this reaction experimentally was measured a non zero asymmetry of emitted gamma quanta and the results was interpreted by the existence of weak non leptonic interaction between nucleons in the compound nucleus. This first experimental result gave a serious impulse of theoretical and experimental developments of parity violation question in nuclear reactions. The weak interaction acts in the background of strong interaction (with order of magnitude higher) and therefore it is very difficult to observe and evidence it. One possibility is the evaluation of asymmetry effects induced by PV phenomena. For neutrons scattering there are a few asymmetry effects (like polarization of incident neutron beam, spin rotation and emitted neutrons asymmetry of incident transversal polarized neutrons) explained by the presence of weak interaction. In natural Lead were observed an unexpected high value of neutron spin rotation due to the PV phenomena. The natural Lead contains four isotopes and the main contribution to the PV effects is given by 204Pb. Further to explain the high value of neutron spin rotation it was supposed the existence of a new negative P resonance with energy EP = - 16 eV. In this work were estimated the PV effects in neutrons scattering in order to extract the weak matrix element and to verify the existence of the new negative resonance of 204Pb nucleus.

At present, more precise data on capture and fission cross-sections and on fluctuation of prompt fission neutron and gamma-ray yields are needed for nuclear industry. A new experimental setup for investigating the resonance neutron induced capture and fission of 239Pu has been constructed at the Frank Laboratory of Neutron Physics. It consists of 2 rings of 12 NaI(Tl) detectors with variable diameter and distance between both rings. Such a setup makes possible to measure the multiplicity, energy and angular distribution of prompt fission gammas. The signals from the 24 detectors are recorded simultaneously in digitized form and stored on the computer hard disks for further off-line analysis.