Use of a 4-circle goniometer for neutron and X-ray diffractometer in the study of single crystals

Objectives. This study described the 4-circle goniometer Syntex P1N and its possible applications in X-ray and neutron structure analysis of single crystals.Methods. The 4-circle goniometer Syntex P1N, due to its high-precision mechanical characteristics and individual components from domestic equipment (sets of DRON type X-ray diffractometers), formed the basis for developing an instrument complex for X-ray and neutron-structure studies.Results. The neutron diffractometer was upgraded based on the Syntex P1N goniometer. Therefore, the 10BF3-based end neutron counter, included in the diffractometer kit, was replaced by the 3He-based domestic side counter, SNM-16. Such a significant reduction in the linear dimensions of the detector allowed us to expand the range of measured angles of 2θ from 90° to 140° and increase the accuracy of the measured interplanar distances accordingly. The goniometer was adjusted relative to the primary neutron beam by placing it on a specially designed plate. Highly accurate measured parameters of the unit cell and the intensity of the reflexes were achieved by optimizing the installation geometry and the protection of the goniometer and detector. Based on the Syntex P1N goniometer, an instrument complex for X-ray diffraction studies has also been developed. Both the developed X-ray and the upgraded neutronography facilities were used to perform experiments to measure the unit cell parameters, the coordinates of atoms, and the parameters of their thermal vibrations on several crystals of domestic synthetic samples: diamond C, silicon Si, halite, or rock salt NaCl, and corundum α-Al2O3. An excellent correlation was achieved by comparing the data obtained with the corresponding chemical crystals’ parameters and reference samples recommended by the International Union of Crystallographers.Conclusions. This paper described a neutron installation and a Syntex P1N neutron diffractometer for the study of single crystals. Based on the latter, an instrument complex for X-ray diffraction studies has also been developed. Experiments on standard samples have shown a high level of accuracy in measuring the lattice parameters, the coordinates of atoms, and the parameters of their thermal vibrations on both the X-ray and neutron diffractometers.

Detector Response to D-D Neutrons and Stability Measurements with 4H Silicon Carbide Detectors

The use of wide-band-gap solid-state neutron detectors is expanding in environments where a compact size and high radiation hardness are needed, such as spallation neutron sources and next-generation fusion machines. Silicon carbide is a very promising material for use as a neutron detector in these fields because of its high resistance to radiation, fast response time, stability and good energy resolution. In this paper, measurements were performed with neutrons from the ISIS spallation source with two different silicon carbide detectors together with stability measurements performed in a laboratory under alpha-particle irradiation for one week. Some consideration to the impact of the casing of the detector on the detector’s counting rate is given. In addition, the detector response to Deuterium-Deuterium (D-D) fusion neutrons is described by comparing neutron measurements at the Frascati Neutron Generator with a GEANT4 simulation. The good stability measurements and the assessment of the detector response function indicate that such a detector can be used as both a neutron counter and spectrometer for 2–4 MeV neutrons. Furthermore, the absence of polarization effects during neutron and alpha irradiation makes silicon carbide an interesting alternative to diamond detectors for fast neutron detection.

The MULTI spectrometer for measurement of β-decay process in exotic nuclei

The construction of the portable spectrometer, MULTI, is designed for the measurement of β-γ-neutron coincidences on beams of radioactive exotic nuclei. It will be used in measurements of the β-decay process of neutron-rich nuclei with large Qβ values accessible in radioactive beams facilities. The experimental technique includes the measurement of the ratios between gamma-ray emission and multi-neutron emission, following beta-decay of radioactive nuclei implanted into an active target. The construction of a gamma-ray spectrometer based on high-volume CeBr3+NaI(Tl) phoswich scintillation detectors is introduced. Results of the measurements of its fundamental characteristics – total detection efficiency, peak efficiency and Compton suppression effect with a 60Co source are presented. Design of the neutron counter array, consisting of 40 proportional counters filled with 3He gas, was optimized with Monte Carlo simulations. Results were validated with a 252Cf spectroscopic source, leading to expected detection efficiency of ∼35% for neutrons with energy < 1MeV. Further development plans are discussed.