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On October 22, 1934, in a fateful experiment, Enrico Fermi and his associates at the University of Rome discovered that neutrons in hydrogen-rich media slow down and acquire enhanced capability for nuclear reactions. The utilization of this phenomenon had far-reaching implications in science and world events. [ABSTRACT FROM AUTHOR]

Aiming to produce a multifunctional efficient shield for gamma rays and slow neutrons simultaneously, a host glass of 30B2O3–10CaO–10ZnO–50Na2O (BCZNPb1) was prepared and reinforced by increasing the PbO and B2O3 concentrations simultaneously to produce three developed glassy materials containing 10 and 35 (BCZNPb2), 20 and 40 (BCZNPb3), and 30 and 45 (BCZNPb4) mol% of PbO and B2O3. Significant structural changes appeared as a result of the incorporation of PbO and B2O3 into the proposed host glass (BCZNPb1), as the network became overcrowded with the four-coordinate tetrahedral units BO4 and PbO4. The structural changes were extensively studied using X-ray diffraction, density and density-based parameters, and Fourier Transform Infrared spectra. Mechanically, the formed BO4 and PbO4 units increased the covalent bonds and the crosslinking density within the glass network, which reflected positively on the improvement of the elastic moduli (modulus of longitudinal, shear, bulk, and Young) and the hardness of the considered glasses. The results of the optical transmittance spectra showed that the produced glassy materials had high transparency, exceeding 70%. The optical band gap and Urbach energy results confirmed the reduction of disorder within the glass network, which resulted from the formation of BO4 and PbO4 units. The attenuation of gamma rays and slow neutrons results showed a significant improvement with increasing the PbO and B2O3 concentrations, as the required half-value layers to attenuate gamma rays decreased by 61.540, 57.790, and 56.699% for the studied gamma ray energies of 661.64, 1173.23, and 1132.51 keV at 30 mol% of PbO (BCZNPb4 glass), respectively, while the required half-value layer for slow neutrons decreased by 61.409% at 45 mol% of B2O3 (BCZNPb4 glass). Accordingly, the produced BCZNPb4 glass has suitable mechanical properties, high transparency, and high attenuation efficiency for gamma rays and slow neutrons, making it a desirable shield in many nuclear domains. [ABSTRACT FROM AUTHOR]

Experiments aimed at studying cluster structures in light nuclei, specifically and in highly excited states of are proposed to be conducted on the Moscow Meson Factory, Institute for Nuclear Research of the Russian Academy of Sciences, neutron channel. This involves the registration of charged particles from the -decay of upon its formation in the C reaction in the intervals between pulses of cascade neutrons. The paper presents the initial results of the experiment on studying the spectra and time distributions of background -quanta and neutrons between accelerator pulses using a proton beam with a frequency of 50 Hz and a duration of 0.3 s. [ABSTRACT FROM AUTHOR]

• Modified B and B/Ti austenitic stainless steels were fabricated and tested to be used as control rods of nuclear reactors. • Structural, mechanical, and slow neutrons attenuation properties of the analyzed stainless steels were studied. • The developed B/Ti austenitic stainless steel was nominated as control rods for nuclear reactors. Modified austenitic stainless steel alloys reinforced with B and B/Ti were fabricated and their suitability as nuclear reactor control rods was tested. A standard stainless steel AISI 316L was used as a base alloy and inlaid by 0.58 wt% of B (SSB). The structural examination of the modified SSB stainless steel, which was conducted through the Schaeffler diagram, optical micrographs (OM), and X-ray diffraction (XRD) patterns had referred to the domination of the austenite phase with the appearance of boride (M 2 B) and carboborides (M 23 X 6) phases along the grain boundaries. Mechanically, an augmentation in the hardness, yield strength (YS), and ultimate tensile strength (UTS) values was observed with the incorporation of B into the AISI 316L stainless steel. However, the addition of B led to a reduction in the values of elongation (El), reduction area (RD), and impact energy. Then, the SSB stainless steel was reinforced by 0.33 wt% of Ti (SSTiB1). The structural examination showed the formation of M 2 B, M 23 X 6 , TiC, TiN, and TiB 2 phases along the grain boundaries of the austenite matrix as well as little ferrite phases. Ti led to a significant increase in hardness, YS, UTS, El, RD, and impact energy of the SSB steel. Finally, a further addition of B and Ti (1.13 & 1.77 wt% of B & Ti, SSTiB2) was tested, as this increase led to the more enhancement of hardness, YS, UTS, and impact energy but reduced the El slightly. Due to the high slow neutrons absorption cross-section of B, the slow neutrons attenuation ability of the modified stainless steel increased effectively with increasing boron concentrations. The obtained distinctive mechanical properties and high attenuation efficiency of slow neutrons of the produced SSBTi2 stainless steel, make it a suitable choice for use as control rods in nuclear reactors. [ABSTRACT FROM AUTHOR]

An experiment devoted to studying neutron-neutron angular correlations in the slow-neutroninduced fission of 233U, 235U and 239Pu nuclei was performed. The experimentally determined angular dependence of the number of neutron-neutron coincidences was compared with the results of a Monte Carlo simulation for various values of the neutron-detection threshold in the range between 490 and 2080 keV. It was found that the experimental angular distributions in question can be described well under the assumption that 2% to 5% of all prompt fission neutrons are emitted isotropically in the laboratory frame. Probably, such neutrons can be interpreted as so-called scission neutrons directly associated with the nuclear-rupture instant. Energy distributions of this component were also obtained from the present analysis. [ABSTRACT FROM AUTHOR]

A novel approach for efficiently imaging objects with slow neutrons in two dimensions is realized. Neutron sensitivity is achieved by use of a boron doped microchannel plate (MCP). The resulting electron avalanche is further amplified with a Z-stack MCP before being sensed by two orthogonally oriented wire planes. Coupling of the wire planes to delay lines efficiently encodes the position information as a time difference. To determine the position resolution, slow neutrons were used to illuminate a Cd-mask placed directly in front of the detector. Peaks in the resulting spectrum exhibited an average peak width of 329 μ m FWHM, corresponding to an average intrinsic resolution of 216 μ m. The center region of the detector exhibits a significantly better spatial resolution with an intrinsic resolution of < 100 μ m observed. [ABSTRACT FROM AUTHOR]

Nondestructive method for analysis of stoichiometric ratio in metal hydrides has been developed. It is based on analysis of total neutron cross sections for hydride samples measured in the area of slow neutrons with use of neutron spectrometry time of flight method. As on titanium hydride example, it is shown, that measurement and analysis of total neutron cross sections for samples TiHn allow to evaluate the value of ratio metal-hydrogen in hydride (n) with accu¬racy ~ 1 %.

A neutron bandpass limiting chopper consisting of up to four discs and a slow neutrons wiper is described. It produces pulses rid of contamination by unwanted slow neutrons. The basic disc works as a single disc chopper and largely defines the TOF resolution. The widths and positions of the slots in an additional disc define the neutron bandpass. The wiper eliminates slow neutrons with wavelengths beyond the working range and can be designed not only as plates connecting the discs, but also as ribs attached to the basic disc, or else as a rotor with blades on one shaft with the basic disc. The TOF resolution can be varied by using constant width slots in the basic disc and moving the chopper as a whole to change the effective disc radius. Two supplementary discs can also be used, one phased with the additional disc to optimize TOF measurements with the detector at different positions and the other phased with the basic disc to vary the TOF resolution. Application of the bandpass limiting choppers in neutron reflectometers at steady flux reactors is considered. [ABSTRACT FROM AUTHOR]

Diamond, with its exceptionally high optical nuclear potential and low absorption cross-section, is a unique material for a series of applications in VCN (very cold neutron) physics and techniques. In particular, powder of diamond nanoparticles provides the best reflector for neutrons in the complete VCN energy range. It allowed also the first observation of quasi-specular reflection of cold neutrons (CN) from disordered medium. Effective critical velocity for such a quasi-specular reflection is higher than that for the best super-mirror. Nano-diamonds survive in high radiation fluxes; therefore they could be used, under certain conditions, in the vicinity of intense neutron sources.

The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter at a reflected neutron source and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. This finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering. [ABSTRACT FROM AUTHOR]

We have combined the low-energy neutron detector WINDS (Wide-angle Inverse-kinematics Neutron Detectors for SHARAQ) and the SAMURAI spectrometer at RIKEN Nishina Center RI Beam Factory (RIBF) in order to perform ( p , n ) reactions in inverse kinematics for unstable nuclei in the mass region around A ∼ 100 . In this setup, WINDS is used for detecting recoil neutrons and the SAMURAI spectrometer is used for tagging decay channel of heavy residue. The first experiment by using the setup was performed to study Gamow–Teller transitions from 132 Sn in April 2014. The atomic number Z and mass-to-charge ratio A / Q of the beam residues were determined from the measurements of time of flight, magnetic rigidity and energy loss. The obtained A / Q and Z resolutions were σ A / Q = 0.14 % and σ Z = 0.22 , respectively. Furthermore, owing to the large momentum acceptance ( 50 % ) of SAMURAI, the beam residues associated with the γ , 1 n and 2 n decay channel were measured in the same magnetic field setting. The kinematic loci of the measured recoil neutron energy and laboratory angle are clearly seen. It shows that the excitation energy up to about 20 MeV can be reconstructed. [ABSTRACT FROM AUTHOR]

We present the design, description, calibration procedure, and an analysis of systematic effects for an apparatus designed to measure the rotation of the plane of polarization of a transversely polarized slow neutron beam as it passes through unpolarized matter. This device is the neutron optical equivalent of a crossed polarizer/analyzer pair familiar from light optics. This apparatus has been used to search for parity violation in the interaction of polarized slow neutrons in matter. Given the brightness of existing slow neutron sources, this apparatus is capable of measuring a neutron rotary power of dφ/dz = 1 x 10-7 rad/m. [ABSTRACT FROM AUTHOR]