R. A. Sadykov

A new type of thermal-neutron detector based on ZnS(Ag)/LiF scintillator and avalanche photodiodes

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.

A system of detection and data acquisition for time-of-flight neutron diffraction setups

A simple system of neutron detection and data acquisition is considered. It is composed of sector sets of 3He 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.

Magnetic structure and spin-glass state of Fe1-xZnxCr2S4 spinels

Fe1-xZnxCr2S4 (0 <x < 1) solid solutions were synthesized and their magnetic properties and structure were investigated. The magnetic phase diagram of the solid-solution system was constructed. The results reveal a ferrimagnetic-spin glass-antiferromagnetic compositional transition in the FeCr2S4-ZnCr2S4 system.

Magnetic Properties and Spin-Glass State of CdCr2 – xInxSe4 and Cd1 – yInyCr2Se4 Solid Solutions

CdCr2 – xInxSe4 and Cd1 – yInyCr2Se4 solid solutions were prepared and their stoichiometry ranges were determined. Increasing the In content was found to increase the lattice parameter and decrease the Curie temperature. In both solid-solution systems, paramagnetic–ferromagnetic–spin-glass phase transitions were revealed.

Scintillation neutron detectors based on solid-state photomultipliers and lightguides

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.

High-Resolution Neutron Diffractometer Based on the IN-06 Pulsed Neutron Source at the Institute for Nuclear Research, Russian Academy of Sciences

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 for a Time-of-flight Diffractometer Based on Linear Scintillation Detectors with Silicon Photomultipliers

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.