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It is proposed that nanosized graphene aggregation could facilitate coherent neutron scattering under particle size conditions similar to nanodiamonds to enhance neutron intensity below cold neutrons. Using the RIKEN accelerator-driven compact neutron source and iMATERIA at J-PARC, we performed neutron measurement experiments, total neutron cross-section and small-angle neutron scattering on nanosized graphene aggregation. For the first time, the measured data revealed that nanosized graphene aggregation increased the total neutron cross-sections and small-angle scattering in the cold neutron energy region. This is most likely due to coherent scattering, resulting in higher neutron intensities, similar to nanodiamonds.

A novel concept of cold neutron source employing chessboard or staircase assemblies of high-aspect-ratio rectangular para-hydrogen moderators with well-developed and practically fully illuminated surfaces of the individual moderators is proposed. An analytic approach for calculating the brightness of para-hydrogen moderators is introduced. Because the brightness gain originates from a near-surface effect resulting from the prevailing single-collision process during thermal-to-cold neutron conversion, high-aspect-ratio rectangular cold moderators offer a significant increase, up to a factor of 10, in cold neutron brightness compared to a voluminous moderator. The obtained results are in excellent agreement with MCNP calculations. The chessboard or staircase assemblies of such moderators facilitate the generation of wide neutron beams with simultaneously higher brightness and intensity compared to a para-hydrogen-based cold neutron source made of a single moderator (either flat or voluminous) of the same cross-section. Analytic model calculations indicate that gains of up to approximately 2.5 in both brightness and intensity can be achieved compared to a source made of a single moderator of the same width. However, these gains are affected by details of the moderator–reflector assembly and should be estimated through dedicated Monte Carlo simulations, which can only be conducted for a particular neutron source and are beyond the scope of this general study. The gain reduction in our study, from a higher value to 2.5, is mostly caused by these two factors: the limited volume of the high-density thermal neutron region surrounding the reactor core or spallation target, which restricts the total length of the moderator assembly, and the finite width of moderator walls. The relatively large length of moderator assemblies results in a significant increase in pulse duration at short pulse neutron sources, making their straightforward use very problematic, though some applications are not excluded. The concept of “low-dimensionality” in moderators is explored, demonstrating that achieving a substantial increase in brightness necessitates moderators to be low-dimensional both geometrically, implying a high aspect ratio, and physically, requiring the moderator’s smallest dimension to be smaller than the characteristic scale of moderator medium (about the mean free path for thermal neutrons). This explains why additional compression of the moderator along the longest direction, effectively giving it a tube-like shape, does not result in a significant brightness increase comparable to the flattening of the moderator.

The present work deals with the modeling of the response to neutrons of heteronuclear diatomic liquids, with special interest in the case of hydrogen deuteride (HD), as a possible candidate for the moderation process required in the production of cold neutrons. Preliminary evaluations of the model giving the neutron double differential cross section of a heteronuclear vibrating rotor were performed in the recent past by using, as a first approximation, the ideal gas law for the center-of-mass translational dynamics. Here, the state-of-the-art methodology (based on the use of quantum simulations of the velocity autocorrelation function) for predicting the neutron response of moderately quantum fluids (like molecular hydrogen and deuterium at low temperatures) is applied to the heteronuclear form of this molecular liquid. The unavailability of the double differential cross section experimental data on liquid HD still compels us to test the calculations only at an integral level, i.e., against the only available measurements of the total neutron cross section of HD. Despite the well-tested and parameter-free computational approach, which includes proper consideration of the quantum effects, the present findings on HD indicate the evident need for more accurate measurements of its total cross section in extended ranges of incident energy, as well as of an experimental determination of the double differential cross section of this mild quantum liquid. For further applicative purposes, a very useful by-product of this study is the determination of the self diffusion coefficient D of the HD in the liquid phase.

In order to determine the capacity of the cold neutron source refrigerator of HANARO, the nuclear heating rate at CN vertical hole is measured by using the heat-flow calorimetric method and confirmed by the calculation. The heating rate measurement device of HANARO was composed of a calorimeter sensor, an air containing aluminum sleeve for fitting the sensor to the CN hole, aluminum weight and a lead wire assembly. The calorimeter sensor consists of a cylindrical Al sample and container, two thermocouples and the electric heater for the calibration of the calorimeter. The sample is separated by an air gap from the Al container surrounded by an air containing Al sleeve. After installation of the calorimeter at a measurement position of HANARO, the heat transfer inside the calorimeter was simulated by the electric heating for the sample. The nuclear heating rates at the CN hole were determined at three reactor powers of 1, 4 and 8 MW by using the calibration curve and the temperature measurements at each reactor power. The measured nuclear heating rate per unit mass of Al sample at 8 MW reactor power is 0.143 W/g and it is equivalent to the 0.494 W/g at 30 MW. The nuclear heating rate was calculated by using the MCNP code. The calculation model for the whole facility including the reactor core and the reflector tank were established. In the calculation procedure, the heat generations by various radiations were evaluated with considering the prompt, delayed and activation effects. The measured heating rate was reasonably well supported by the calculation using the cold neutron facility design code. It will be very useful for the moderator cell of cold neutron source of HANARO.

Intense sources of very cold neutrons (VCNs) would be beneficial for various neutron scattering techniques and low-energy particle physics experiments. Binary clathrate hydrates hosting deuterated tetrahydrofuran (THF-d) and dioxygen show promise as potential moderators for such sources due to a rich spectrum of localized low-energy excitations of the encaged guest molecules. In this article, we present a reliable manufacturing technique for such hydrates. Neutron diffraction data confirm their clathrate structure as type II (CS-II), determine their purity, and cage occupancy. Furthermore, we present data on the thermal expansivity of THF-d– and THF-d–O2clathrates, drawing attention to them as an interesting case study for the complex structure and dynamics of this class of material.

The cold neutron imaging and diffraction instrument IMAT at the second target station of the pulsed neutron source ISIS is currently being commissioned and prepared for user operation. IMAT will enable white-beam neutron radiography and tomography. One of the benefits of operating on a pulsed source is to determine the neutron energy via a time of flight measurement, thus enabling energy-selective and energy-dispersive neutron imaging, for maximizing image contrasts between given materials and for mapping structure and microstructure properties. We survey the hardware and software components for data collection and image analysis on IMAT, and provide a step-by-step procedure for operating the instrument for energy-dispersive imaging using a two-phase metal test object as an example.

The radiation shielding characterization of glasses is vital in establishing their role in nuclear protection applications. This study presents the influence of reducing PbF 2 content on the radiation shielding parameters of x CaF 2 –(25- x )PbF 2 –25Bi 2 O 3 –49.8B 2 O 3 –0.2Cr 2 O 3 glasses where x  = 0, 5, 15, and 25 mol % represents the glass code, Ca/Pb-BBC1, Ca/Pb-BBC2, Ca/Pb-BBC3, and Ca/Pb-BBC4, respectively. Photon and cold neutron transmission parameters were evaluated through the use of FUKA simulations and confirmed by WinXCOM (for photons only) calculations. On the other hand, the shielding quantities for electron, proton, alpha particle, and carbon ions were estimated from ESTAR, PSTAR, ASTAR, and SRIM codes. While the fast neutron removal cross section and interaction cross sections for thermal neutrons were estimated through analytic expressions. The value of mass attenuation coefficient decreased from 4.178–0.042, 4.086–0.042, 3.846–0.040, and 3.550–0.039 cm −2 /g for Ca/Pb-BBC1—4 accordingly as photon energy increased from 0.1 to 10 MeV. Analysis of other calculated photon absorbing quantities such as effective atomic number, half value layer, and gamma-ray dose constant shows that the increase in the PbF 2 content increased the photon shielding ability of the glasses. A similar effect was observed for charged particle absorption. A comparison of the photon and neutron absorbing capacity of the Ca/Pb-BBC glasses with those of common radiation shields shows that the Ca/Pb-BBC glasses have capacity to shield gamma rays and neutrons better. The Ca/Pb-BBC glasses hence are attractive for radiation protection functions such as for the storage of nuclear waste and laboratory radiation sources and shielding in contemporary and future applications of radiation.

The design of a time-of-flight neutron reflectometer proposed for the new generation of compact neutron sources is presented. The reflectometer offers the possibility to use spin-polarized neutrons. The reflectometer design presented here takes advantage of a cold neutron source and uses neutrons with wavelengths in the range of 2–15 Å for the unpolarized mode. In general, due to tight spatial restrictions and the need to avoid moving parts inside the beam channel, a multi-channel collimator guide and reflective neutron guide are used for the first section of the instrument. This enables definition of the desired wavelength band and easy selection of one out of three different Q-resolutions. A low background for the collimator system and the reflectometer is ensured by employing a tangential beam channel and an in-channel sapphire filter. The second section is the time-of-flight (TOF) system, which uses a double-disk neutron chopper followed by polarization elements, the sample environment and the neutron detector system. Monte Carlo simulations and neutron beamline intensity measurements are presented. The design considerations are adoptable for neutron sources where space is limited and sections of the instrument are in a high-radiation environment.

Neutrons have been used in a wide field of applications by using various neutron sources. Material science is one of the widest research fields. The activity is supported by nuclear research reactors and high-intensity spallation neutron sources based on a high-intensity proton accelerator. However, it is desired to perform a measurement when researchers want to do and to perform adventuresome experiments that have not yet confirmed its importance. Furthermore, trial and error measurements are necessary to improve a measurement method. Compact accelerator-driven neutron sources are suitable for such usage and in some cases can complement the measurement at a large facility. The use of the compact neutron source has sometimes led to new methods. Other than material science, a new application of soft error acceleration test has been performed at the compact accelerator-driven neutron sources. Another neutron application is radiation therapy called as boron neutron capture therapy. In this field, nuclear reactor neutron sources have been used but many of them shut down. It was desired to construct the BNCT facility near a hospital. Therefore, BNCT facilities based on the compact accelerator have been constructed in the world. Here, the neutron sources and new methods and applications developing at compact accelerator-driven neutron sources are introduced.

A novel non-destructive testing scanning system based on a large-size line array fast neutron detector and compact D-T neutron source has been constructed. The scanning range is up to 1000 mm, and the resolution is better than 1 mm. The fast neutron detection subsystem consists of a polypropylene zinc sulfide scintillator embedded with wavelength-shifting fibers, coupled with a light lens and a scientific CCD camera. With a new rotating tritium target, the lifetime of the compact D-T neutron source could achieve ten hours. The experimental results indicate that the scanning method based on line array fast neutron detector and D-T neutron source is feasible and enables the detection of slits on the order of 0.5 mm in width. Fast neutron tomography has been realized by this detection system too.