A neutron gate is proposed for the accumulator with nonmagnetic walls. The gate is a part of the accumulator wall to which a magnetic field is applied during the neutron pulse as inflow of neutrons into the accumulator occurs. At this time, the gate operates based on the compensation of the nuclear potential of the neutron interaction by the magnetic potential. In intervals between neutron pulses, the probability of neutron absorption in the gate and in the entire accumulator is defined by the subbarrier reflection of neutrons from the accumulator wall, being as small as 10–5−10–4

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.

The neutron Fourier diffractometer FSS (Fourier Strain Scanner) was used between 1990 and 2010 at the FRG-1 stationary reactor at the GKSS research center (Geesthacht, Germany) for the study of residual stresses in structural materials and industrial products. In 2010, the FRG-1 reactor was finally decommissioned. In this regard, the FSS diffractometer was transported to the Frank Laboratory of Neutron Physics of JINR (Dubna, Russia) in 2014 and installed on channel no. 13 of the IBR-2 pulsed reactor. The results of upgrading the instrument and further prospects for its development are presented.

— 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.

The high-resolution Fourier diffractometer (HRFD) operates at the IBR-2 pulsed reactor, on which the correlation method of data registering has been implemented using a fast Fourier chopper and specialized electronics. A wide-aperture ring back-scattering detector for HRFD has been developed. The detector consists of six Z n S ( A g ) / 6 L i F-scintillation rings, each one of which is divided into 12 sections. Main parameters of this detector: covered solid angle 2 θ = ( 133 − 175 ) ∘ ; Ω d ≈ 2.0 sr; average absorption efficiency 85 %, geometric contribution to resolution Δ d / d < 0.0005. The concept of a detector and its data acquisition system are presented.

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.

Three neutron instruments at the Neutron Physics Laboratory (NPL) in Řež near Prague — small-angle scattering (SANS) MAUD, strain scanner SPN-100 and strain diffractometer TKSN-400 — have been modernized recently with new 2D position-sensitive detectors (PSDs) from JINR, Dubna. Here we report on the progress made in relation to the possibilities of the diffractometers due to the improved performance of the detectors. The first part of the paper is dedicated to a detailed description of the hardware and software of the PSDs, as well as its integration with the in-house experimental control software. Then practical examples of neutron scattering experiments for each of the upgraded facilities are presented.

A specialized diffractometer intended for use in studying real-time transient processes in condensed media, which also allows the recording of Bragg diffraction and small-angle neutron scattering spectra, has been created at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research. Frequently, only the given formulation of the experiment with the continuous recording of information on the process enables us to obtain data required for the correct interpretation of events. One of the crucial parameters of such experiments is the minimal time interval in which sufficient statistics can be acquired. The diffractometer parameters make it possible to measure diffraction and small-angle spectra within minute and even second (for certain types of transition processes) ranges. The possibilities of neutron scattering are discussed as applied to the study of transient processes, the diffractometer design is described, and its main characteristics and the test experiment results are presented.

The high-resolution Fourier diffractometer (HRFD) was commissioned at the IBR-2 pulsed reactor at FLNP JINR in 1994. The specific feature of the HRFD design is the use of fast Fourier chopper for modulating the primary neutron beam intensity and the correlation method of diffraction data acquisition. This allowed to reach with HRFD extremely high resolution (Δ d / d ≈ 0.001) over a wide range of inter-planar spacings at a relatively short flight path between chopper and sample ( L = 20 m). Over time, a lot of diffraction experiments on crystalline materials, the main goal of which was to study their atomic and magnetic structures, were performed at HRFD. Successful implementation of the Fourier diffractometry technique at the IBR-2 reactor stimulated the construction of yet another Fourier diffractometer intended for internal mechanical stress studies in bulk materials (FSD, Fourier Stress Diffractometer). In this paper the experience of using this technique at the IBR-2, which is a long-pulse neutron source, is considered, the examples of HRFD studies are given, and possible solutions for existing technical problems of using correlation diffractometry and ways of increasing the intensity and resolution of HRFD are discussed.

Описана модернизация детекторной системы и системы управления нейтронным порошковым дифрактометром (н.п.д.) на канале ГЭК-5 реактора ВВР-ц (филиал ФГУП “НИФХИ им. Л.Я. Карпова”, Обнинск). Cоздан подключенный к персональному компьютеру аппаратно-программный комплекс, обеспечивающий сбор и накопление данных, а также управление экспериментом. Кратко описаны разработанные в ЛНФ ОИЯИ основные блоки системы автоматизации н.п.д. и управляющего программного комплекса Sonix+. Модернизация позволила увеличить светосилу дифрактометра и полностью автоматизировать процесс измерений.

A new gas multi-section ring-shaped detector (MSRD) for thermal neutrons has been developed at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) for ...

A new gaseous annular sectional thermal-neutron detector for the new neutron diffractometer at the IBR-2 reactor has been designed and manufactured at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research (JINR). The detector is designed to study small-volume samples at high pressure and consists of 16 sections, each one of which is divided into six independent detector elements. We present the main design features of the detector, detecting electronics, data-acquisition and visualization software, and software system for experiment management. The results of the first neutronographic experiments that were carried out with the use of the detector are also presented.

The modernization of the detector system and control system of the neutron powder diffractometer (NPD) in the GEK-5 channel of the VVR-c reactor (Obninsk Branch, Karpov Institute of Physical Chemistry) is described. The PC-connected hardware and software complex, which ensures data acquisition and storage and control of the experiments, is created. The main modules of the NPD automation system and Sonix+ control software package, designed at the Frank Laboratory of Neutron Physics at JINR, are briefly described. The modernization has made it possible to increase the luminosity of the diffractometer and completely automatize the measurement process.

A vertically loaded shaft cryostat based on a closed-cycle cryocooler built around a Sumitomo SRP-062B pulse tube has been developed. The cryostat is intended for investigating the structure and phase transformations of materials via neutron diffraction experiments on samples at pressures up to 10 GPa created in high-pressure chambers with sapphire and diamond an vils in the temperature range of 6-300 K. The cryostat has been tested with the help of the DISK diffractometer of the Russian Research Centre Kurchatov Institute. A high-pressure chamber is loaded into the cryostat through its shaft with the help of an insert. The chamber is cooled by heat-exchange gas (helium-4) an d a heat exchanger that is thermally connected with the cryocooler's second stage. The minimum attained temperature of a sample is 6 K. The drift diameter of the shaft is 120 mm, making it possible to cool chambers with lengths up to 200 mm (in the vertical orientation) and 110 mm (in the horizontal orientation). The cryostat has been designed and manufactured at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research.

The Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research is one of the leading centers of neutron research in Russia. Within the works on the modernization of detector systems, researchers of the laboratory have designed and fabricated linear and area gas-filled position-sensitive detectors of thermal neutrons and the area monitor detector with a low attenuation of the incoming beam. These devices and their main characteristics have been described.

Neutron guides are widely used to transport the neutrons from the moderator to the sample. Due to the constructive features of the ring corridor of the fast pulsed reactor IBR-2, the minimal distance between the moderator and the guide entrance is around 6m. The main goal of the paper is to optimize the neutron optical system between the moderator and the entrance of the new neutron guides. Using Monte Carlo simulations we calculate the possible best gain of the neutron flux density at the guide exit. After the described optimization process, the optimal system is obtained. The recommendations for construction of the new beam line are provided too. Similar technique and the proposed system could be easily adapted for another similar beam line at the neutron sources.

Development of new high-flux-intensity neutron sources and the need to equip them with efficient spectrometers raises the problem of designing special-purpose direct-beam monitors-detectors. These detectors feature an extremely low efficiency and a very low attenuation of the incident neutron beam. In this work, a two-coordinate position-sensitive monitor-detector is described that was developed for real-time recording of the profile of neutron beams generated by both steady and pulsed neutron sources. The basic parameters of this device are the following: a coordinate resolution of 4 × 4 mm2, a sensitive area of 100 × 100 mm2, and a recording efficiency of 10−6−10−2. Use of nitrogen as a converter makes it possible to achieve a record low efficiency and still maintain other parameters at a desired level. The device can be combined not only with high-flux-intensity neutron sources already in use worldwide but also with next-generation sources being developed in the United States (SNS) and Japan (JPARC).

A one-dimensional position-sensitive detector of thermal neutrons has been developed to equip high-efficiency neutron spectrometers at the ИБР-2 research reactor. The detector is based on a multiwire proportional chamber filled with a mixture of 3He + CF4 and has an active area of 200 × 80 mm and a spatial resolution of 2 mm. The detector has been used to good effect in the REFLEX and HRFD spectrometers of the ИБР-2 reactor, as well as in the diffraction facility of the ИВВ-2M research reactor (Zarechnyi, Russia).

. At the IBR-2 pulsed reactor in Dubna a new neutron Fourier diffractometer FSD is under construction. FSD continues the development of neutron Fourier diffractometry at long-pulse neutron sources, which was started several years ago with the high-resolution Fourier diffractometer HRFD at the IBR-2. Whereas HRFD is mainly used for precise structural refinement, FSD is optimised for internal stress measurements in bulk materials. The FSD design satisfies the requirements of high luminosity, high resolution, a specific sample environment, a wide range of d hkl , and fixed scattering angles 2θ=±90°. It consists of a mirror neutron guide, a fast Fourier chopper for the neutron-beam intensity modulation, a ±90° MultiCon ZnS(Ag) 6 Li-loaded detector system with both geometrical and electronic focusing, a five-axis goniometer ‘Huber’ and loading machines, and VME-based RTOF analysers for data acquisition. Examples of the first experimental results obtained with FSD are presented.