IBR-2 Reactor Research Articles

Modeling of the focusing device and the elliptical neutron guide for the DN-6 diffractometer at IBR-2 reactor

Possible options for modernization of the neutron beam forming system of the DN-6 diffractometer for the study of crystal and magnetic structures of microsamples at high pressures are being considered. It was demonstrated that for samples with the cross-section not exceeding 5×5 mm2 the most efficient option would be the use of an elliptical neutron guide. It allows to deliver neutrons for large distances from the source to samples with minimal losses using, as a rule, just one neutron reflection per dimension i.e. one at a side and one at top or bottom. For the present moment due to technical difficulties of such option realization, the simplified solution was proposed. At the end of the curved neutron guide it is planned to install a vertical plane focusing 7-meter-long parabolic section. Such a modernization will increase the neutron flux at the sample by a factor 1.5–3.5 and reduce respectively the typical measurement times.

Optimization and Comparing a Different Various of Head Part of a Moderator of “Central” Direction for IBR-2 Reactor

The performance of the upstream moderator for neutron beams 1, 4, 5, 6, and 9 extracted from the IBR-2 reactor is simulated towards selecting its optimum configuration. For different moderator options, gain factors with respect to the existing comb-shaped water moderator are computed. Taking into account the technological issues in manufacturing a combined moderator, the scheme with optimal physical characteristics is selected.

Small-angle neutron scattering investigations of Co-doped iron oxide nanoparticles. Preliminary results

Preliminary small-angle neutron scattering investigations on aqueous suspensions of several cobalt doped ferrites (CoxFe3-xO4, x=0; 0.5; 1) nanoparticles prepared by chemical co-precipitation method, are reported. The measurements were accomplished at the YuMO instrument in function at the IBR-2 reactor. Results of intermediary data treatment are presented and discussed.

Studies of electrochemical interfaces by TOF neutron reflectometry at the IBR-2 reactor

The operation performance of electrochemical energy conversion and storage systems such as supercapacitors and batteries depends on the processes occurring at the electrochemical interfaces, where charge separation and chemical reactions occur. Here, we report about the tests of the neutron reflectometry cells specially designed for operando studies of structural changes at the electrochemical interfaces between solid electrodes and liquid electrolytes. The cells are compatible with anhydrous electrolytes with organic solvents, which are employed today in all lithium ion batteries and most supercapacitors. The sensitivity of neutron reflectometry applied at the time-of-flight (TOF) reflectometer at the pulsed reactor IBR-2 is discussed regarding the effect of solid electrolyte interphase (SEI) formation on metal electrode surface.

Analysis of arsenic and mercury content in human remains of the 16th and 17th centuries from Moscow Kremlin necropolises by neutron activation analysis at the IREN facility and the IBR-2 reactor FLNP JINR

A neutron activation analysis (NAA) of three samples of human remains of the 16th and 17th centuries from the necropolises of the Moscow Kremlin has been carried out at FLNP JINR. The samples were irradiated at two facilities: the IREN source of resonance neutrons and the IBR-2 reactor. Spectra of the induced activity of the irradiated samples were measured by using the automatic measurement system developed at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR). This system consists of a high-purity germanium detector with spectrometric electronics, a sample changer, and control software. Mass fraction of arsenic, mercury, and some other elements were calculated using two NAA methods—relative and absolute. The obtained values confirm the fact of acute mercury poisoning of Anastasia Romanovna, the first wife of Tsar Ivan Vasil’evich the Terrible, the first Russian Tsarina (died in 1560). High levels of mercury were detected in the bone remains of Tsarevich Ivan Ivanovich (died in 1581), the son of Tsar Ivan the Terrible, and Prince Mikhail Vasil’evich Skopin-Shuiskii (died in 1610). The results provide an opportunity to introduce into scientific circulation the exact values of mass fraction of mercury, arsenic, and other elements in the samples taken from the burials of the Russian historical figures of the second half of 16th–early 17th century.

Neutron time-of-flight reflectometer GRAINS with horizontal sample plane at the IBR-2 reactor: Possibilities and prospects

A new time-of-flight neutron reflectometer GRAINS with a horizontal sample plane (vertical scattering plane) has recently been put into operation at the pulsed reactor IBR-2 (JINR, Dubna). The scattering geometry applied makes it possible to carry out complex studies of nanostructured interfaces in solid and liquid states by measuring the specular reflectivity and the intensity of diffuse scattering of thermal neutrons from open surfaces and hidden interlayer boundaries, including solid-liquid interfaces, over a wide momentum transfer range. The classical analysis of specular reflectivity allows one to determine the scattering length density profile in the object under study in a direction perpendicular to the interface for a thickness of ~100 nm with a resolution of 1 nm. The analysis of off-specular (diffuse) neutron scattering makes it possible to characterize lateral correlations on surfaces and interlayer boundaries. The paper summarizes the first experience in the operation of the GRAINS reflectometer. The instrument characteristics are presented together with the possibilities for experiments with solid and liquid samples illustrated with simple systems. Further steps for the development of the reflectometer are discussed.

The influence of neutron radiation damage on the optical properties of plastic scintillator UPS 923A

Plastic scintillators are vital in the reconstruction of hadronic particle energy and tracks resulting from the collision of high energy particles in the Large Hadron Collider (LHC) at CERN. These plastic scintillators are exposed to harsh radiation environments and are susceptible to radiation damage. The effects of radiation damage on the transmittance, luminescence and light yield of Ukraine polystyrene-based scintillator UPS 923A were studied. Samples were irradiated with fast neutrons, of varying energies and fluences, using the IBR-2 reactor FLNP (Frank Laboratory for Nuclear Problems) at the Joint Institute for Nuclear Research. Results show a small change in the transmittance of the higher energy visible spectrum, and a noticeable change in the light yield of the samples as a result of the damage. There is no change observed on the luminescence as a result of radiation damage at studied fluences. The doses and uences of the neutrons shall be increased and changes in optical properties as a result of the radiation shall be further studied.

Expected performance of time-gradient magnetic field SESANS diffractometer at pulsed reactor IBR-2

The application of the time-gradient magnetic field neutron spin-echo technique (TGF-NSE) aiming to extend the possibilities of the REFLEX reflectometer at the pulsed reactor IBR-2 (Dubna, Russia) towards a high and medium resolution small-angle scattering is considered. This technique requires the use of a linearly increasing magnetic field in the form of the sequence of saw-teeth pulses. Such a technique is well-suited to the pulsed structure of the neutron beam at the IBR-2 reactor. The wide range of neutron wavelengths employed in the time-of-flight (TOF) operation mode allows for the simultaneous coverage of a wide range of spin-echo lengths (corresponding to a wide Q-range in conventional SANS). Virtual experiments carried out using the VITESS simulation package demonstrate that such a setup at IBR-2 will allow for the coverage of the length scales from 100 Å to 6000 Å in a single instrument setting. The use of the TGF-NSE technique in the TOF mode leads to gaps in the measured SANS curves due to the jumps of magnetic field at the end of saw-teeth pulses. However, crucially, these do not harm the quality of the data. Moreover, the lost data can be retrieved by an additional measurement with a delayed start of the magnetic pulse sequence.

III International Conference on Small Angle Neutron Scattering dedicated to the 80 anniversary of Yu.M. Ostanevich

Preface“Among the many well-known fundamental and applied consequences of neutron discovery, one of the first was the emergence of structural neutron diffraction - one of the methods for studying the spatial structure of condensed matter at the atomic level. Investigating the dynamics of biological macromolecules by neutron diffraction methods is an area that is almost untouched. We believe that also in this direction one should expect rapid progress.”Yu.M.Ostanevich and I.N.Serdyuk Uspekhi Fizicheskih Nauk (1982)More than 30 years after Ostanevich and Serdyuk reviewed the then 50 years from the neutron discovery, we are happy to support their statement and prediction by reporting on the further progress in the field of neutron scattering research. Frank Laboratory of Neutron Physics has organized the III International Conference on Small Angle Neutron Scattering (YuMO2016) that was – not coincidently – dedicated to the 80th anniversary of Ostanevich.Yuriy Mechislavovich Ostanevich (1936–1992) has had a determinative and crucial contribution to the construction of spectrometers at the pulsed reactor IBR in Dubna, Russia. He contributed in particular to the development of time-of-flight small-angle neutron scattering (SANS) technique, and the selection of advanced scientific areas for its application. The SANS instrument at the IBR-2 reactor is called YuMO in his honour. The Ostanevich’s leadership and outstanding scientific achievements in SANS studies of polyelectrolytes, small molecules, fractals, metallic glasses, macromolecules, polymers, etc., were recognized also by a number of awards including the State Prize of the Russian Federation in 2000. To this end of course, we should not forget mentioning the contribution of close collaborators of Ostanevich: Laszlo Cser, Josef Plestil as well as Alexander Kunchenko, Vadim Bezzabotnov and Nikolay Gorski.The YuMO2016 conference focused on providing opportunities to discuss various possibilities of exploiting the SANS technique in the many aspects of condensed matter research as once appreciated and predicted by Ostanevich, and perhaps even surpassing his predictions. The FLNP have had an opportunity to welcome more than 110 participants from 14 different countries and 3 continents comprising Europe, North America and Australia. The scientific program was filled with 43 oral presentations extending over 930 minutes, while more than 60 posters were presented during the poster sessions and breaks.The content of the conference and its proceedings are fully commensurate with world-wide trends in neutron scattering applications. The contribution dedicated to the SANS methods and instrumentation describes for example a role of polarized neutrons in the localization of free radicals in the structural biology. It is hard to imagine another probe than neutron, and another technique than small-angle scattering that have such many utilization possibilities in the studies of drug delivery systems, neurodegenerative diseases, and other aspects of biomembranes and soft matter in general, to name but a few.Besides the neutron’s sensitivity to the light elements, and H/D differentiation making the hydrogen-rich biomaterials an innate target, magnetism is accessible to neutrons too. Our proceedings document studies where neutron scattering techniques come to the rescue when other methods have failed, and/or provide examples of synergy between the various methods. Atomic force microscopy, NMR, Raman spectroscopy, molecular dynamics simulations, and X-ray scattering are clearly the complementary methods of choice for condensed matter research. It is a matter of time, and already happening future in some cases, for the studies concerning nanoparticles and nanocomposites to spin-off into advanced and industrial applications.It is more than intriguing to realize the role of neutrons and/or small angle scattering method in such studies across various scientific fields. The neutron history is written by those who touched the neutron. Let us pay a tribute to one of them. We are fortunate to open our collection of YuMO2016 conference dedicated to the 80th anniversary of Yu.M. Ostanevich by the very personal commemorations of his close colleague and friend Dr. Laszlo Cser.NORBERT KUČERKA, MARIA BALASOIU, AND ALEXANDER I. KUKLINFrank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, RussiaApril 2017

On the theory of pneumotransport of beads in cold neutron moderator of the IBR-2 reactor

The paper presents some aspects of pneumotransport theory of solid ball motion along a pipeline of complex geometry having application for the pelletized cold moderator of the IBR-2 reactor. Motion equations for a ball carrying by gas flow along a round tube both smooth and rough, are obtained. Aerodynamics forces and momentum of forces, acting on the ball depending on its velocity are defined on the base of numerical modeling of ball movement, and analytical simplified model of pneumotransport of balls along round tube is created. This model meets the demand for practical application as it shows satisfactory agreement with experimental modelling of ball movement in a glass tube. One of important results of the work is giving proofs of irregular movement of ball along a tube stipulated by roughness of the tube side.

Neutron Sources at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research

The IBR-2 reactor and IREN facility are the two main neutron sources at the Frank Laboratory of Neutron Physics. This contribution presents data on the IBR-2 reactor parameters before and after modernization. The general schemes of the IBR-2 reactor as well as of the IREN facility are presented.

Determination of the origin of the medieval glass bracelets discovered in Dubna, Moscow region, Russia using the neutron activation analysis

The work is dedicated to the determination of the origin of archaeological finds from medieval glass using the method of neutron activation analysis (NAA). Among such objects we can discover not only things produced in ancient Russian glassmaking workshops but also imported from Byzantium. The authors substantiate the ancient Russian origin of the medieval glass bracelets of pre-Mongol period, found on the ancient Dubna settlement. The conclusions are based on data about the glass chemical composition obtained as a result of NAA of 10 fragments of bracelets at the IBR-2 reactor (Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research).

Prompt fission neutron investigation in 235U(nth,f) reaction

The prompt neutron emission in thermal neutron induced fission of 235 U has been investigated applying digital signal electronics. The goal was to compare the results of this digital data acquisition and digital signal processing analysis to the results of the pioneering work of Apalin et al. Using a twin Frisch grid ionization chamber for the fission fragment detection and a NE213 equivalent neutron detector in total about 10 6 neutron coincidences have been registered. The fission fragment kinetic energy, mass and angular distribution has been investigated along with prompt neutron time of flight and pulse shape using a six channel synchronous waveform digitizer with sampling frequency of 250 MHz and 12 bit resolution. The signals have been analyzed using digital pulse processing algorithms, developed by authors. The thermal neutron beam was transported from the IBR-2 reactor to the target with bent mirror neutron guide.

Possibility of loading the chamber of the “central” pelletized cold moderator for IBR-2 reactor beams 1, 4–6, and 9

This paper presents the results of experiments performed at the cold moderator test stand with beams 1, 4–6, and 9 for studying the possibility of loading the moderator chamber with frozen balls (pellets) 3.5 to 3.8 mm in diameter through the cryogenic pipeline of complex configuration with a 4-m-long section ascending at an angle of 50°. The optimum parameters for the successful loading of the moderator chamber are found to be the following: mass flow rate of the carrier gas (helium), 2 g/s; temperature of the pipeline walls and helium, 79–85 K; angular velocity of the disc in the ball dispenser, 3.6°/0.5 s; ball ejection rate from the dispenser to the pipeline, 8 balls/s; and maximum chamber loading time, 6 h. During the construction of the test stand, the cryostat is replaced with a new one with two gas blowers, which is necessary for maintaining a low temperature in two independent cooling circuits (for two cold moderators or for a cold moderator and the test stand) and the software for the control of the operation parameters is modified.

De-Li-DAQ-2D – a new data acquisition system for position-sensitive neutron detectors with delay-line readout

Software for a data acquisition system of modern one- and two-dimensional position-sensitive detectors with delay-line readout, which includes a software interface to a new electronic module De-Li-DAQ-2D with a USB interface, is presented. The new system after successful tests on the stand and on several spectrometers of the IBR-2 reactor has been integrated into the software complex SONIX+ [1]. The De-Li- DAQ-2D module [2] contains an 8-channel time-code converter (TDC-GPX) with a time resolution of 80 ps, field programmable gate array (FPGA), 1 Gbyte histogram memory and high-speed interface with a fiber-optic communication line. A real count rate is no less than 106 events/s. The De-Li-DAQ-2D module is implemented in the NIM standard. The De-Li-DAQ-2D module can operate in two modes: histogram mode and list mode.

Pelletized cold moderator of the IBR-2 reactor: current status and future development

Current status and future development of the pelletized cold moderator of the IBR-2 reactor in Neutron Physics Laboratory of JINR are represented. Nowadays cold moderator works for physical experiments and allows conducting experiments in the region of wavelengths more than 4 Å up to 10-13 times faster in comparison with the warm water moderator. Future development of the pelletized cold moderator is aimed at increasing the time of its operation for experiments and is based on three components: creation of a system of continuous charging and discharging of beads, supplementation of various additives, and use of new materials, such as triphenylmethane.

On the use of a composite moderator at the IBR-2 reactor: Advantages for the neutron-diffraction texture analysis of rocks

A unique cold moderator based on a mixture of mesitylene and m-xylene is developed for the IBR-2 pulsed reactor. If combined with a standard warm-water moderator, it provides a high neutron flux in a wide wavelength range. The advantages of the use of this composite moderator in neutron-diffraction texture analysis are discussed using the example of a sample of slate (formed from five minerals) studied using the SKAT diffractometer. The diffraction data obtained in experiments with warm-water and composite moderators are compared.

Condensed matter research at the modernized IBR-2 reactor: from functional materials to nanobiotechnologies

An overview of the main scientific areas of condensed matter research, which are extended with the use of the IBR-2 high-flux research reactor, is presented. It is demonstrated that the spectrometer facility of the upgraded reactor has great potential for studying the structural, magnetic, and dynamical properties of novel functional materials and nanobiosystems, which ensures the leading position of the Joint Institute for Nuclear Research in neutron research of condensed matter for the long-term prospect.

New generation of data acquisition and data storage systems of the IBR-2 reactor spectrometers complex

The paper presents an overview of works on the creation of data acquisition and data storage systems, which have been carried out in the Department of the IBR-2 spectrometers complex (DCS) of the Frank Laboratory of Neutron Physics (FLNP) over the past 15 years (before, during, and after the modernization of the IBR-2 reactor). These systems represent a unified set of identical (from the viewpoint of hardware) modules limited in type but functionally complete, wherein distinctions in parameters, functional capabilities, encoding, correction and preliminary data processing procedures specific to each spectrometer are realized on the level of microprograms, electronic tables, and integrated software control system.

Magnetostructural phase transitions in NiO and MnO: Neutron diffraction data

Structural and magnetic phase transitions in NiO and MnO antiferromagnets have been studied by high-precision neutron diffraction. The experiments have been performed on a high-resolution Fourier diffractometer (pulsed reactor IBR-2), which has the record resolution for the interplanar distance and a high intensity in the region of large interplanar distances; as a result, the characteristics of both transitions have been determined simultaneously. It has been shown that the structural and magnetic transitions in MnO occur synchronously and their temperatures coincide within the experimental errors: Tstr ≈ Tmag ≈ (119 ± 1) K. The measurements for NiO have been performed with powders with different average sizes of crystallites (~1500 nm and ~138 nm). It has been found that the transition temperatures differ by ~50 K: Tstr = (471 ± 3) K, Tmag = (523 ± 2) K. It has been argued that a unified mechanism of the “unsplit” magnetic and structural phase transition at a temperature of Tmag is implemented in MnO and NiO. Deviation from this scenario in the behavior of NiO is explained by the quantitative difference—a weak coupling between the magnetic and secondary structural order parameters.