Neutron scintillation detectors based on ZnS(Ag)/LiF, solid-state photomultipliers, and an organic glass light guide developed at the Institute for Nuclear Research, Russian Academy of Sciences (INR RAS) are successfully used in neutron diffractometers facilities at the INR RAS as a replacement for standard counters based on 3He. These detectors use optical light guides with diffuse reflection, which makes it possible to multiply the recorded signal (up to 95 photoelectrons) in comparison with detectors with wavelength shifting fibers. The article describes two types of bias circuit for silicon photomultipliers. A method of dynamic bias has been proposed, which makes it possible to reduce the recovery time of a silicon photomultiplier and to increase the loading capacity of neutron detectors by a factor of 8. Simulation and comparison of two types of preamplifiers showed an increase in the loading capacity. The new electronics makes it possible to increase the loading capacity of the detectors up to 400 kHz. A circuit for digital control of discrimination thresholds has been developed and described. A new data acquisition system for time-of-flight neutron diffractometers for 80 detectors with the possibility of scaling has been developed.

The efficiency of multilayer scintillation neutron detectors (counters) based on ZnS(Ag) : 6 LiF, designed at the Institute for Nuclear Research, Russian Academy of Sciences, is analyzed by Monte Carlo simulation. The spectral dependence of the counter efficiency on the angle of incidence of the neutron beam is obtained. A series of numerical experiments is performed using the model of a time-of-flight powder diffractometer with ring detectors, based on the developed counters, with the aim of estimating its resolution. The results obtained are useful for optimizing the configuration of counters and related detecting units, while maintaining their compactness and ease of manufacture.

New neutron scintillation detectors based on silicon photomultipliers and organic-glass light guides are described. This type of detector may become an alternative to gas-filled detectors, in which the medium used (3He) is expensive. In this work, ZnS:6LiF(Ag) is used as a scintillator with a calculated efficiency of 42% for thermal neutrons. An optically transparent plastic is used as the light guide. The dimensions of the finished detector are 60 × 5 × 5 mm. The thickness of the scintillator layers is fixed and equal to 0.5 mm. The fiber thickness is varied in the range from 0.3 to 1.8 mm depending on the number of scintillator layers; it is limited by the total detector thickness. A method for manufacturing and joining together such scintillation detectors is described. The first results of testing neutron counters with different numbers of scintillator layers are presented. When using two scintillator layers, the efficiency of this neutron-detector type is 42%. With an increase in the number of scintillator layers to five, the efficiency increased to 90%.

The results of Monte Carlo simulation and test reflectometry experiments on the "Gorizont" neutron reflectometer (on the IN-06 pulsed neutron source at INR RAS) after its upgrade with a two-dimensional detector with a positioning system are presented. The two-dimensional detector makes it possible to use the instrument not only for neutron reflectometry, but also for small angle neutron scattering. Estimates of the instrument resolution and the spectra of the neutron beam at different collimations have been obtained using Monte Carlo simulation. Test reflectometry experiments have been performed on mirrors with known characteristics. The characteristics match the manufacturer's data with an error of 5%, obtained from the simulation.

The cryogenic system for maintaining a target at a constant temperature in the range 5–25 K after shutting off the pulse tube (PT) cryogenic refrigerator is developed and tested. The temperature stability at the sample is ±2 mK for at least 20 hours. The cryogenic setup consists of cryostat, PT cryocooler, liquid helium vessel, helium gas supply, thermo-radiation shield, thermal resistance. The system provides 0.25 W of cooling power at the target. The appropriate thermal resistance should be used for different temperatures. The designed operation mode is 3 minutes off and 15 minutes on. The deactivation of PT cryocooler allows to achieve the target position stability of 1 micrometer or less during the X-ray characterization. The effect of neutron-shield was estimated using Monte-Carlo simulation.

The RADEX pulsed neutron source based on a linear proton accelerator at the Institute for Nuclear Research, the Russian Academy of Sciences, has one vertical channel with a 4-m path length and three horizontal channels with path lengths of approximately 10, 20, 30, and 50 m. The source is characterized by an unconventional configuration: the target and the water moderator are located perpendicularly to the proton beam; as a result, the neutron spectrum is enriched with epithermal and cascade neutrons. Using the source, investigations in the fields of nuclear physics, condensed-matter physics and nanostructures can be performed. The results obtained using various path lengths of horizontal channels of the RADEX neutron source are presented. Test measurements are conducted and direct beam spectra for the horizontal neutron channels and neutron diffraction patterns of test samples are obtained. The resolution for different path lengths of the neutron source is determined. The possibility of performing phase analysis is demonstrated.

A high-resolution neutron diffractometer has been fabricated on the basis of an IN-06 pulsed neutron source at the Institute for Nuclear Research, Russian Academy of Sciences. The diffractometer incorporates two blocks of detectors with helium neutron counters and time-of-flight (TOF) focusing at scattering angles of 156°–165°. A block of new-type high-efficiency scintillation detectors of thermal neutrons based on a ZnS(Ag)/LiF scintillator and silicon photomultipliers with TOF focusing is developed and tested. Test measurements are performed, and the diffractometer resolution is estimated. The diffraction pattern of nonmagnetic NiCrAl alloy is measured and used to determine the phase composition by means of the Rietveld method. It is demonstrated that the given setup can be applied to phase analysis.

A ring neutron detector has been developed for a time-of-flight diffractometer based on linear scintillation detectors. Light is transported over an organic glass light guide with a diffuse reflector. This scheme makes it possible to collect more photons than are collected in detectors based on wavelength-shifting fibers and to use avalanche photodiodes (SiPMs) instead of photomultiplier tubes. Testing confirmed that these detectors could be used as an alternative for widely used proportional neutron counters filled with 3He.

Neutron detectors based on scintillation screens ZnS(Ag)/LiF and solid-state photomultipliers have been developed. Lightguides are used to collect light. The application of a coincidence scheme provides a low dark count and a neutron detection efficiency as high as 70%. A scheme of x-y neutron detector based on wavelength shifting fibers is also proposed. Tests of the proposed versions of detectors in a neutron beam have shown their efficiency.

The diffraction of neutrons at a single crystal of potassium bromide in experiments performed at the 50-m-long baseline of the RADEX facility at the Institute for Nuclear Research in February 2012 is studied. The neutron-beam parameters are determined. The effect of splitting of the 200 reflection in the region of the p -wave resonance of 81 Br is found. The mosaicity of the studied sample is estimated. The estimate is indicative of the fine quality of the single crystal of potassium bromide.

В Институте ядерных исследований РАН (г. Троицк) введен в эксплуатацию импульсный нейтронный источник ИН-06 (spallation source). Измерены спектры нейтронов прямых пучков экспериментальных каналов импульсного источника, предназначенного для исследований конденсированных сред, наносистем и функциональных материалов. Cравнение расчетных и экспериментальных нейтронных спектров показывает их хорошее совпадение. Приводятся данные по плотности нейтронных потоков при заданных параметрах работы линейного ускорителя протонов, являющегося драйвером нейтронного источника ИН-06.

Исследована дифракция нейтронов на монокристалле бромида калия на 50-метровой пролетной базе установки РАДЭКС ИЯИ РАН во время февральского сеанса 2012 года. Определены параметры пучка нейтронов. Обнаружен эффект расщепления рефлекса 200 в области р-волнового резонанса 81Br. Получена оценка мозаичности исследуемого образца, которая свидетельствует о хорошем качестве монокристалла бромида калия.

A high-efficiency thermal-neutron detector based on ZnS(Ag)/LiF scintillator is described, which employs a new technique of signal pick-up with the aid of a light guide and avalanche photodiodes instead of optical fibers and photomultipliers. Results of tests on the RADEX pulsed neutron source are presented, in which neutron diffraction patterns of test objects have been obtained.

At the Institute of Nuclear Research, Russian Academy of Sciences, a pulse neutron source IN-06 (spallation source) is commissioned. The direct-beam neutron spectra from experimental channels of the pulse source intended for use in studying condensed media, nanosystems and functional materials are recorded. A comparison of the simulated and experimental neutron spectra shows good agreement. Data for the density of neutron beams at the given functional parameters of the linear proton accelerator, which is the driver of the IN-06 neutron source, are presented.

A simple system of neutron detection and data acquisition is considered. It is composed of sector sets of 3 He counters, timing amplifiers-discriminators, 8-stop time-to-digital converters (TDCs), and a gate duration generator, as well as branch and crate controllers coupled to a computer. The system is used in neutron diffraction setups on the neutron spallation source at the Institute for Nuclear Research. The output pulse from the timing amplifier-discriminator is timed with the fast electron component of an avalanche in the detector. Neutron time-of-flight spectra are formed by a TDC in its embedded memory over the recording enable time ranging from 1 to 63 ms. The TDC time range has 4096 gradations with time step of 0.125–128 μs. Fast data acquisition is ensured by the Linux kernel driver. The data acquisition software based on the Qt4 library recognizes modules in the CAMAC crate and displays spectra with their preliminary processing.