The high-resolution Fourier diffractometer (HRFD) has been in routine operation since 1994 at the long-pulse neutron source, the IBR-2 reactor, in Dubna. Its fast Fourier chopper provides probably the best compromise between very high resolution in reciprocal space (Δd/d ≈ 0.001) and the intensity. For further improving intensity of TOF-diffraction pattern, a wide-aperture ring backscattering detector (BSD) has been developed on the basis of ZnS(Ag)/6LiF scintillator. BSD is designed in the form of 6 concentric rings, each of which is subdivided into 12 identical parts. The main parameters of the detector are the following: range of scattering angles is 2θ = (133 - 175) degrees, covered solid angle is Ωd ≈ 2.0 sr, average percentage absorption efficiency gets closer to 85%, geometrical contribution to resolution function does not exceed Δd/d = 0.0005. In the report the concept of the detector is described and its data acquisition system is presented. The start of operation of the detector at the HRFD is scheduled for 2024.

Тонкопленочные конвертеры нейтронов на основе карбида бора B4C, обогащенного изотопом 10В, наносимые на подложки из алюминия, алюминиевой фольги и полимерных пленок большой площади, являются перспективным материалом для создания новых детекторов нейтронов. Нанесение пленок B4C методом магнетронного распыления на такие основания сильно осложняется необходимостью нагрева подложек до температуры 400 °С и более, что может приводить к их деформации. В работе показано, что применение ионного ассистирования в процессе магнетронного осаждения B4C приводит к формированию пленок нанокристаллической структуры, обладающих высокой прочностью и гибкостью, даже при понижении температуры подложки до 50 °С, а использование подслоя алюминия повышает адгезию. Получены тонкие пленки B4C на подложках из алюминия 0,5 × 100 × 100 мм2 и 0,5 × 280 × 400 мм2 в атмосфере аргона при температуре 400, 200 и 50 °С. Исследованы структура, состав и показатель преломления по пленкам на пластинах из кремния. Гибкость получаемых пленок и низкая температура формирования дают возможность нанесения конвертера нейтронов из 10B4C на тонкие полимерные основания.

— One of the most important activities of the IBR-2 DSC is the development of detector technologies, which will be used as a basis in designing detectors for future experiments. Detector systems developed by the IBR-2 DSC are described. Today they are used to good effect in research facilities or are prepared for application in the foreseeable future.

This article discusses the results of parallel measurements with two-coordinate position-sensitive He(3)detectors with a delay line, which are installed on REFLEX and GRAINS neutron spectrometers of the IBR-2 pulsed reactor with the simultaneous use of three data acquisition systems: DeLiDAQ-1, DeLiDAQ-2, and a system based on the N6730 digitizer produced by CAEN.

The heterogeneous ferromagnetic–superconducting layered heterostructures V/Fe0.7V0.3/V/Fe0.7V0.3/Nb and Nb/Ni0.65(0.81)Cu0.35(0.19), which contain magnetic clusters and ferromagnetic domains, are studied. The magnetic and superconducting properties of the structures depend on the magnetic-layer thickness, the magnetic field, and the time elapsed from structure preparation. We detected the interaction of clusters with a domain structure, diamagnetism and magnetization reversal of the magnetic layer during the superconducting transition in a ferromagnetic–superconducting heterostructure, and a superconducting transition in the magnetic layer. The magnetic and resistive properties of the heterostructures changed in several weeks and months.

The efficiency calculation of different variants of assembly designs consisting of 3, 4 and 5 Helium-41 type counters are presented. Optimization of the geometric parameters of the assemblies has been carried out to increase the homogeneity of efficiency and to simplify the design of the detector system. The GEANT4 package has been used to simulate the operation of the modules designed to replace the old counters of the spectrometer NERA at the IBR-2 reactor. The calculation results have been compared with the experimental ones.

Recently we have performed a comparative study of the characteristics of the data acquisition systems for the position-sensitive detectors with a delay line operating on the neutron instruments of the IBR-2 reactor. As a result, to have an optimal version of electronics we have chosen two directions of further development: the DeLiDAQ-2 system for high-flux measurements and the CAEN N6730 digitizerbased system for high-precision experiments. The study has also revealed an urgent need to integrate list mode measurements into the experiment control system on some of the neutron spectrometers. So far, the experiment control system SONIX operating on most of the IBR-2 spectrometers has received and displayed the data measured in the histogram mode. The report, besides the results of the comparative study, describes the software that is developed to solve the task of formation of events from raw data, their sorting, selecting by appropriate criteria, and histogramming as well as to be appropriate for integration into the SONIX. The proposed solutions are not limited to any specific types of electronics for PSD.

The possible concepts whereby a time-of-flight small-angle diffractometer optimized for a neutron moderator operating in the cold (at 30 K) and thermal (at 300 K) modes can be implemented at the IBR-2 reactor are studied on the basis of numerical calculations. Under cold conditions, the peak of the neutronbeam energy spectrum is shifted toward low energies (long wavelengths). This extends the sensitivity range of the instrument with respect to the sizes of the objects under study (1–100 nm and higher). A classical scheme enabling the separation of thermal/cold neutrons (E ~10–3–10–2 eV) from the background (formed mainly by fast neutrons), which is based on bent neutron-optical devices, is discussed. Due to restrictions imposed by the geometry of the beamline within which the instrument is planned to be located, a configuration with a short multichannel mirror device for beam bending (beam bender) is preferable. Simulation and optimization of the proposed small-angle instrument is carried out taking into account the real beamline geometry and the available space in the experimental reactor hall. A comparison of the setup has been made with the facility based on the curved neutron guide and the facility with direct view of the moderator.

На основе численных расчетов изучены возможные концепции реализации на реакторе ИБР-2 малоуг- лового времяпролетного дифрактометра, оптимизированного для двух режимов работы замедлителя нейтронов - холодного (температура 30 К) и теплового (температура 300 К). В холодном режиме максимум энергетического спектра нейтронов в пучке смещен в область низких энергий (больших длин волн), что расширяет диапазон чувствительности установки в отношении размеров исследуемых объектов (1-100 нм и выше). Рассмотрена классическая схема отделения тепловых/холодных нейтронов (E ~10-3-10-2 эВ) от фона (сформированного, главным образом, быстрыми нейтронами) на основе изогнутых нейтронно-оптических устройств. Из-за ограничений, накладываемых геометрией канала, на котором планируется поместить установку, предпочтительной является конфигурация с коротким многоканальным зеркальным устройством отклонения пучка. Выполнены моделирование и оптимизация предполагаемой малоугловой установки с учетом реальной геометрии канала и доступного места в экспериментальном зале реактора. Проведено сравнение с установкой на основе изогнутого нейтроновода и установкой с прямой видимостью замедлителя.

The variety of research being conducted at the instruments on the external beams of the IBR-2M pulsed fast reactor in Frank Laboratory of Neutron Physics Joint Institute for Nuclear Research (FLNP JINR) is the reason of the differences in the requirements of the detectors for these instruments. This leads to the necessity of developing a variety of detectors in the Laboratory that are used in experiments. This report reviews the neutron detection systems developed and used at the instruments on the external beams of the IBR-2M pulsed research reactor, the current status and operating features of which have been considered.

The article reviews thermal neutron detector developments in the Department of the IBR-2 Spectrometer Complex of the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research (FLNP JINR). A variety of detector types are considered: neutron monitors, ring detectors, position-sensitive detectors (PSD), and scintillation detectors. The experience of exploitation of these detectors at the research facilities of the FLNP JINR is presented.

We have studied the Nb(70 nm)/Ni0.65Cu0.35(6.5 nm)/Si layered structure in the temperature range T = 1.5–10 K using polarized neutron reflectometry. The correlation of the states of magnetic structures is observed at temperature T = 9 K, which is slightly higher than the superconducting transition temperature Tc = 8.5 K of the structure. At temperature T = 4 K, which is lower than Tc, the effect of reflexivity of magnetic states existing at T = 9 K was observed.

High-performance cold neutron moderator for the IBR-2 reactor is manufactured at the Frank Laboratory of Neuron Physics and operates in normal mode at present. Material for cold moderator is mixture of mesitylene and m-xylene in the form of solid beads with diameter of about 3-4mm. These beads are replaced in the moderator’s chamber periodically. Uniformity of chamber volume filling is one of the problems of moderator operation. Observation of filling process is realized by acquisition of 2D images of moderator on two coordinate PSD by the method of “camera-obscura”. Ready-built monitoring system allows controlling the level of working medium in chamber of moderator, to measure neutron spectra and to control of warming and drain of used mesitylene. At the present time monitoring system is installed at 8th channel of IBR-2 reactor, it detects 12times gain of 6-10Å neutron flux with using of new moderator. Also absence of appreciable spectrum degradation was observed.