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In the early 1930's, Fermi wrote two papers in which he introduced the concepts of "scattering length" and "pseudopotential." Since that time, these terms have become universally associated with low energy scattering phenomena. Even though the two papers are very different—one in atomic physics, the other in neutron physics—a simple figure underlies both. The figure appears many times in Fermi's work. We review how the two papers came about and briefly discuss modern developments of the work that Fermi initiated with these two remarkable papers. [ABSTRACT FROM AUTHOR]

Neutron depolarization experiments have shown that the intragranular magnetic domain structure of polycrystalline ferrites exhibits a marked grain size dependence. Below a grain size of around $3~\mu \text{m}$ , the magnetic domain structure changes from the two-domain to the mono-domain state. Ferrites composed of mono-domain grains exhibit low dissipation at megahertz frequencies. This is attributed to the absence of intragranular domain wall movement, i.e., a microscopic origin for dissipation in ferrites has been identified. The implications of this clear observation and evidence for a transition from the mono- to two-domain state in ferrites for micromagnetic theory when a single particle becomes monodomain, as well as for the initial permeability mechanisms in polycrystalline ferrites, are discussed. [ABSTRACT FROM AUTHOR]

This paper present the impact on hardness assurance testing and the enhanced degradation of proton and neutron of the semiconductor device. In this work, it is shown that protons and neutrons can induce enhanced degradation in both trench and planar geometry power MOSFETs. Specifically, large shifts in current-voltage characteristics of some devices were observed at extremely low proton total dose levels (as low as 2 rad(SiO2)). These shifts induced significant increases (more than three orders of magnitude) in device "off" state leakage current. Neutron irradiations show similar degradation at equivalent fluence levels, even though neutrons do not deposit dose due to direct ionization. In addition, this increase in leakage current occurs at a much lower total dose level than expected based on 60Co gamma ray data. These data therefore suggest that the mechanism responsible for the enhanced degradation is a microdose effect associated with secondary particles produced through nuclear interactions between protons and neutrons and the materials in integrated circuits. The secondary particles deposit enough charge in the gate oxide to induce a parasitic drain to source leakage path in the transistor. Although the results are demonstrated for only trench and planar geometry power MOSFETs, microdose effects can impact the radiation response of other integrated circuit types. [ABSTRACT FROM PUBLISHER]

This paper is a review of the present status of neutrino mass physics, which grew out of an APS sponsored study of neutrinos in 2004. After a discussion of the present knowledge of neutrino masses and mixing and some popular ways to probe the new physics implied by recent data, it summarizes what can be learned about neutrino interactions as well as the nature of new physics beyond the Standard Model from the various proposed neutrino experiments. The intriguing possibility that neutrino mass physics may be at the heart of our understanding of a long standing puzzle of cosmology, i.e. the origin of matter-antimatter asymmetry is also discussed. [ABSTRACT FROM AUTHOR]

Fracture structures are important natural gas transport spaces in shale gas reservoirs, and their storage state in shale gas reservoirs seriously affects gas production and extraction efficiency. This work uses numerical modeling techniques to investigate the logging response law of the thermal and epithermal neutrons in the gas-containing fracture environment at various angles, applying neutron logging as a technical method. To increase the precision of the evaluation of the natural gas storage condition in shale gas reservoirs, the angle of the fractures' neutron logging data is analyzed. It is found that even in an environment with the same porosity of the fractures, there are significant differences in the logging results due to the different angles of the fracture alignment: 1. the neutron counts in the high-angle (70–90°) fracture environment are 2.25 times higher than in the low-angle (0–20°), but the diffusion area of the neutrons is only 10.58% of that in the low-angle (0–20°); 2. in the neutron energy spectrum, neutron counts are spreading to the high-energy region (7–13 MeV) along with the increase in the angle of the fracture, and the feature is especially prominent in the approximately vertical (60–90°) fracture environment, which is an increase of 528.12% in comparison with the counts in the approximately horizontal angle (0–30°) environment. The main reason for these differences is the variation in the volume of the fracture within the source radiation. This volumetric difference results from the variation in fracture angles (even though the fracture porosity is the same). In view of the above phenomenon, this paper proposes the concept of "effective fracture volume", which can intuitively reflect the degree of influence of fracture angle on neutron logging results. Further, based on the unique characteristics of shale gas reservoirs and neutrons, this paper provides important theoretical support for the modification of the porosity of the field operation, the evaluation of the physical characteristics of the gas endowment space, and the assessment. [ABSTRACT FROM AUTHOR]

Computed tomography has become a standard method to probe processes in porous media. Neutrons enabled us to better study the dynamics of hydrogeneous fluids in the matrix of dense and opaque materials. We review recent instrumentation and method improvements to the neutron imaging facilities NEUTRA and ICON at Paul Scherrer Institute. The improvements give us higher spatial resolution making it possible to follow finer details and faster acquisition to increase the CT volume capture rate. The combination with new reconstruction techniques improve the information output with less acquired projection data and hence providing higher volume rates. Bi-modality is a further option to provide more information about the sample and the processes taking place. These features make new neutron imaging experiments to investigate the fluid distribution in porous samples possible. We demonstrate the performance on a selection of experiments performed at our neutron imaging instruments. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) are subjected to varying conditions of temperature during their lifetime. Using a combination of neutron reflectometry and in situ photoluminescence spectroscopy we show that layers typically found in OLEDs can interdiffuse. The diffusion is temperature dependent and it is found that the iridium(III) complexes can be remarkably mobile, even with relatively bulky alkyl groups attached to the ligand. [ABSTRACT FROM AUTHOR]

This paper investigates the possibility of restoring the trajectory of fission fragments using thick targets that are opaque to the fragments, by analyzing the angular distribution of prompt neutrons. Employing thick targets in experimental studies with low-intensity neutron beams accelerate the accumulation of statistics, thereby facilitating the study of subtle effects, such as the rotation (ROT) effect which sheds light on the deformation and rotational behavior of fission fragments. The paper details the experimental techniques used, presents the results of neutron yield measurements from the fission of 235U with cold and “warm” (60 meV) neutrons in the range of angles from 0 to 360( (in 22.5( increments). The analysis of these is also presented. [ABSTRACT FROM AUTHOR]

In this paper, an overview of wide-bandgap (WBG) semiconductors for radiation detection applications is given. The recent advancements in the fabrication of high-quality wafers have enabled remarkable WBG semiconductor device applications. The most common 4H-SiC, GaN, and β-Ga2O3 devices used for radiation detection are described. The 4H-SiC and GaN devices have already achieved exceptional results in the detection of alpha particles and neutrons, thermal neutrons in particular. While β-Ga2O3 devices have not yet reached the same level of technological maturity (compared to 4H-SiC and GaN), their current achievements for X-ray detection indicate great potential and promising prospects for future applications. [ABSTRACT FROM AUTHOR]

Understanding the behaviour of a neutron spectrum with burnup is important for describing various phenomena associated with reactor operation. The quest to understand the neutron spectrum comes with a lot of questions. One question that is usually asked by students is: Does the neutron spectrum harden or soften with burnup? Most textbooks used by students do not provide a definite answer to this question. This paper seeks to answer this question using a 3D model of a standard 17 × 17 pressurised water reactor fuel assembly. Two cases were studied using the Serpent Monte Carlo code: the first considered the fuel assembly with constant boron concentration (traditionally found in many published papers), and the second considered boron iteration (where the boron concentration was reduced with burnup). Neutron spectra for the two cases at beginning of life and end of life were compared for spectral shifts. In addition, thermal spectral indices were used to assess spectrum hardening or softening with burnup. Spectral shifts to lower energies were observed in the thermal region of the neutron spectrum, whereas the fast region experienced no spectral shift. There was an increase in thermal spectral indices indicating that the spectrum became soft with burnup. [ABSTRACT FROM AUTHOR]

The deterministic methods are efficient for solving the neutron transport equation (NTE), but suffer from discretization errors. The increasingly complex geometric models make spatial discretization errors the primary source of discretization errors. Considering that spatial discretization errors come from inaccurate geometric shape descriptions and low-accuracy numerical schemes, this paper develops a Discontinuous Galerkin Finite Element Method for the NTE on unstructured polygonal meshes to reduce spatial discretization errors. In this method, the physical modal basis is adopted to handle the polygonal mesh and to achieve high-order accuracy in a uniform and efficient way. The numerical results of various fixed-source and k-eigenvalue benchmarks demonstrate that the method developed in this paper can give accurate solutions on polygonal meshes with high convergence rates. [ABSTRACT FROM AUTHOR]

Neutron and X-ray computed tomography (NCT and XCT, respectively) are imaging techniques that are increasingly applied in geomechanics research. They are used to non-destructively reveal different microstructural aspects of geomaterials: XCT is often used to observe/quantify differences in density or porosity, while NCT reveals the presence and distribution of hydrogenous materials such as water. The correlated use of NCT and XCT for geomechanics and geotechnics research is in its infancy. To this date, very few experiments have been carried out that combine both techniques, and none has been used to investigate geomaterial–structure interaction. This paper presents the first correlative NCT–XCT imaging study of pile installation. A scaled model pile was installed in an unsaturated intact chalk cylinder and in situ NCT and ex-situ XCT synchrotron-based imaging was applied consecutively. Chalk was used because the behaviour of displacement piles installed in this material is still subject to considerable uncertainty. Results reveal for the first time the interaction between installation-induced changes in chalk density and water distribution variations, with evidence of water displacement into the densified material in the vicinity of the installed pile. A straightforward method for correlative bulk density–moisture content determination from NCT–XCT images of geomaterials is presented and their limitations are discussed. [ABSTRACT FROM AUTHOR]

We discuss the quantum-bouncer experiment involving ultracold neutrons in a braneworld scenario. Extra-dimensional theories typically predict the strengthening of gravitational interactions over short distances. In this paper, we specifically study the anomalous gravitational interaction between the bouncing neutron and the reflecting mirror, resulting from hidden dimensions, and investigate the effects of this new interaction on the outcome of the quantum-bouncer experiment in the context of a thick brane model. This analysis allows us to identify which physical quantity of the extra-dimensional theory this neutron experiment is capable of constraining. Based on the experimental data, we found a new and independent empirical bound on the free parameters of the model: the higher-dimensional gravitational constant and a parameter related to a transverse width of the confined matter inside the thickbrane. This new bound is valid in scenarios with an arbitrary number of extra dimensions greater than two. In this manner, by considering the thickness of the brane, we have been able to extend previous studies on this topic, which were limited to models with few codimensions, due to non-computability problems of power-law corrections of the gravitational potential. [ABSTRACT FROM AUTHOR]

This paper concerns the correlation of hard x-ray and neutron signals, which were recorded with scintillation detectors oriented in the axial and radial directions, in a comparison with interferometric and extreme-ultraviolet radiation frames, as recorded within the plasma focus (PF)-1000 facility operated with a deuterium filling. The considered signals showed two different phases. In the initial phase, the fusion neutrons are mainly produced by deuterons moving dominantly downstream during the disruption of a pinch constriction (lasting tens nanoseconds). In the later phase (usually after about 100 ns), the fusion neutron emission reaches its maximum in the radial directions. This emission (lasting 100–200 ns) is caused by the fast deuterons moving in both the downstream and radial directions. It correlates usually with a decay of dense plasma structures in remnants of the expanding pinch column. This can be explained by a decay of internal magnetic fields. The neutron signal is usually composed of several sub-pulses of different energies. It was deduced that the primary deuterons producing the observed fusion neutrons undergo a regular and repeated temporal, directional, and energy evolution. [ABSTRACT FROM AUTHOR]

We present the first machine learning-based autonomous hyperspectral neutron computed tomography experiment performed at the Spallation Neutron Source. Hyperspectral neutron computed tomography allows the characterization of samples by enabling the reconstruction of crystallographic information and elemental/isotopic composition of objects relevant to materials science. High quality reconstructions using traditional algorithms such as the filtered back projection require a high signal-to-noise ratio across a wide wavelength range combined with a large number of projections. This results in scan times of several days to acquire hundreds of hyperspectral projections, during which end users have minimal feedback. To address these challenges, a golden ratio scanning protocol combined with model-based image reconstruction algorithms have been proposed. This novel approach enables high quality real-time reconstructions from streaming experimental data, thus providing feedback to users, while requiring fewer yet a fixed number of projections compared to the filtered back projection method. In this paper, we propose a novel machine learning criterion that can terminate a streaming neutron tomography scan once sufficient information is obtained based on the current set of measurements. Our decision criterion uses a quality score which combines a reference-free image quality metric computed using a pre-trained deep neural network with a metric that measures differences between consecutive reconstructions. The results show that our method can reduce the measurement time by approximately a factor of five compared to a baseline method based on filtered back projection for the samples we studied while automatically terminating the scans. [ABSTRACT FROM AUTHOR]

In response to the significant dependency on empirical judgment in measuring the prompt neutron decay constant with the traditional Rossi-alpha method and the issue of requiring an excessive number of detectors with the DMD-Rossi-alpha method, this paper introduces a calculation method for the prompt neutron decay constant based on a combination of Latin Hypercube Sampling (LHS), Dynamic Mode Decomposition (DMD), and the Rossi-alpha method. Initially, the method uses LHS to expand the sample dataset of neutron noise data to reduce the number of detectors required. It then employs the Rossi-alpha method to construct a Rossi-alpha distribution model from neutron noise data. Finally, it utilizes DMD for feature extraction from the Rossi-alpha distribution model, thereby determining the prompt neutron decay constant. Research findings demonstrate that, by simulating the KUCA facility using RMC3.5 in a near-critical state, the relative error of the α value calculated by the LHS-DMD-Rossi-alpha method model is 9% less than that calculated by the Rossi-alpha method. This approach, capable of enhancing the precision of measuring the prompt neutron decay constant with just a single detector, holds significant theoretical value and engineering significance for the advancement of reactor physics and experimental techniques. [ABSTRACT FROM AUTHOR]

With neutron diffraction, the local stress and texture of metallic components can be analyzed non-destructively. For both, highly accurate positioning of the sample is essential, requiring the measurement at the same sample location from different directions. Current sample-positioning systems in neutron diffraction instruments combine XYZ tables and Eulerian cradles to enable the accurate six-degree-of-freedom (6DoF) handling of samples. However, these systems are not flexible enough. The choice of the rotation center and their range of motion are limited. Industrial six-axis robots have the necessary flexibility, but they lack the required absolute accuracy. This paper proposes a visual servoing system consisting of an industrial six-axis robot enhanced with a high-precision multi-camera tracking system. Its goal is to achieve an absolute positioning accuracy of better than 50 μ m. A digital twin integrates various data sources from the instrument and the sample in order to enable a fully automatic measurement procedure. This system is also highly relevant for other kinds of processes that require the accurate and flexible handling of objects and tools, e.g., robotic surgery or industrial printing on 3D surfaces. [ABSTRACT FROM AUTHOR]

There are many studies in Odd–Even staggering (OES) of nuclear masses, but the research on nuclear masses by using the systematicness of OES is indeed very few. In this work, we analyze the relationship among the four neighboring nuclei based on the OES of nuclide chain with the same number of neutrons in atomic mass evaluation database (AME2016 database). Our purpose in this paper is to describe an empirical formula with one constant for OES of nuclear masses that can be useful in describing and predicting nuclear masses with mass number A ≥ 1 0 0. With the empirical formula and AME2016 database, the root-mean-square deviation (RMSD) of the nuclei that we have successfully obtained 172 keV for A ≥ 1 0 0 (the RMSD is 140 keV for A ≥ 1 5 8). This paper also uses Levenberg–Marquart (L-M) neural network approach to study the OES of nuclear masses (A ≥ 1 0 0 , RMSD ≃ 1 4 3 keV; A ≥ 1 5 8 , RMSD ≃ 1 1 9 keV). The results show that the RMSD of nuclear masses for A ≥ 1 0 0 based on neural network approach 30 keV decreases than that based on empirical formula (the accuracy is increased by about 17%). In addition, the predicted values based on the empirical formula and L-M neural network approach are consistent with the values in AME2020 database, and the difference between our predicted values based on AME2016 database and experimental values measured in recent years is small. These results show that the new relation for nuclear masses has good simplicity, accuracy and reliability. Accurate nuclear mass is helpful to the research of nuclear physics, nuclear technology and astrophysics. [ABSTRACT FROM AUTHOR]

In heavy-ion-induced projectile fragmentation reactions at Fermi energies vast amount of different nuclides far from stability line are born. These neutron or proton-reach isotopes can be used as secondary beams to obtain even more exotic new isotopes or to study nuclear interactions of halo nuclei and their radii and other yet unsolved scientific problems. Radioactive isotopes produced in fragmentation reactions can be used in medical and industrial applications. In this paper we present velocity and isotope distributions of fragments from Na to Ca obtained in the collision of Ar beam of 36.5 MeV on Be target on COMBAS mass-spectrometer at FLNR, JINR. We compare the experimental results with the calculations fulfilled in combined transport-statistical model and show good agreement between them. [ABSTRACT FROM AUTHOR]

The existing interpretation models for the time spectrum of impulse neutron oxygen activation require interpreters to select the peak range or background range manually from the time spectrum curve, and there is no adaptive interpretation model that can determine the peak range or background range. In this paper, an adaptive selection rule for background segment is proposed, and a semiautomatic interpretation model is constructed by combining background segment interpretation model. Firstly, the interpretation operator selects the time spectrum curve, then the algorithm program adaptively determines the background segment according to the rules, and then calculates and displays the transit time and volume flow according to the background segment interpretation model. The processing results of the measured data show that the interpretation model in this paper not only retains the interpretation precision of the background interpretation model, but also reduces the labor intensity of the interpretation operator, realizing the semiautomatic interpretation of the time spectrum. [ABSTRACT FROM AUTHOR]

Neutron star observations, as well as experiments on neutron-rich nuclei, used to motivate one to look at degenerate nuclear matter from its extreme, namely, pure neutron matter. As an important next step, impurities and clusters in dilute neutron matter have attracted special attention. In this paper, we review in-medium properties of these objects on the basis of the physics of polarons, which have been recently realized in ultracold atomic experiments. We discuss how such atomic and nuclear systems are related to each other in terms of polarons. In addition to the interdisciplinary understanding of in-medium nuclear clusters, it is shown that the quasiparticle energy of a single proton in neutron matter is associated with the symmetry energy, implying a novel route toward the nuclear equation of state from the neutron-rich side. [ABSTRACT FROM AUTHOR]

This paper investigates the neutron diffusion model with two energy groups in spherical reactors. In particular, the integer-order two energy groups neutron diffusion model in spherical reactors is resolved using the Laplace transform method by regarding the spherical radius r as a time domain. Next, we transform the neutron diffusion model into fractional-order versions using the Caputo differentiator, resulting in what is referred to as the fractional-order two-energy-group neutron diffusion model. To address this fractional-order system, we introduce a novel approach to reduce a system of 2a -order to a duplicated system of a -order, where 0 <α 1. This converted system is then solved using one of the recent modifications of the fractional Euler method called the Modified Fractional Euler Method (MFEM). Several numerical simulations are depicted to verify our findings. [ABSTRACT FROM AUTHOR]

The isotopic shifts of 149Sm–150Sm and 157Gd–158Gd have often been observed in meteorites and lunar surface materials, because they result from the neutron-capture reactions associated with secondary neutrons produced by cosmic-ray irradiation. While the Sm and Gd isotopic shifts can mainly be used for the estimation of thermal neutron fluences that of 167Er–168Er has recently been applied in the estimation of epithermal neutron fluences. The systematic isotopic dataset of Sm, Gd and Er helps us to consider the details of planetary materials' cosmic-ray exposure conditions using the balance of the fluences between thermal and epithermal neutrons. This paper reviews a series of isotopic variations of Sm, Gd, and Er in association with neutron-capture reactions for the application of planetary sciences. As a new attempt and possibility for better understanding the neutron fluence and its energy distribution, the use of Yb isotopic variation is then discussed using two different data sources, namely lunar regolith and the Oklo natural reactors. Finally, the preliminary result for the precise isotopic measurement of Yb is presented from the viewpoint of chemical separation and instrumental improvement. [ABSTRACT FROM AUTHOR]

Neutron star observations, as well as experiments on neutron-rich nuclei, used to motivate one to look at degenerate nuclear matter from its extreme, namely, pure neutron matter. As an important next step, impurities and clusters in dilute neutron matter have attracted special attention. In this paper, we review in-medium properties of these objects on the basis of the physics of polarons, which have been recently realized in ultracold atomic experiments. We discuss how such atomic and nuclear systems are related to each other in terms of polarons. In addition to the interdisciplinary understanding of in-medium nuclear clusters, it is shown that the quasiparticle energy of a single proton in neutron matter is associated with the symmetry energy, implying a novel route toward the nuclear equation of state from the neutron-rich side. [ABSTRACT FROM AUTHOR]

Before the Fukushima Daiichi Nuclear Power Plant (NPP) accident, the prospect of expanding the nuclear power plants fuel base was also associated with the use of MOX fuel (mixed oxide uranium-plutonium fuel). The Fukushima Daiichi nuclear accident, which has led to the reactor core meltdown, revealed an insufficient knowledge of the fuel nuclides temperature properties in a temperature range wider than the operating temperatures ranges of existing reactors (above 1000 K). The paper presents the results of calculating the temperature dependences of the fission and radiative capture nuclear reactions cross-sections averaged over the thermal neutron spectrum for uranium 238, uranium 235 and plutonium 239. A fundamental difference in the temperature dependences of the uranium 235 and plutonium 239 nuclear reactions cross sections averaged over the thermal neutron spectrum is found and explained for the studied temperature range. The temperature dependences of the heat sources densities for MOX fuel and uranium oxide fuel for thermal reactors are calculated as well. For the first time, the fundamental difference between the temperature dependences of the heat sources densities for the MOX fuel and uranium oxide fuel is shown. The accident dynamics theory based on the fundamental difference in the temperature dependences of the heat sources densities for the MOX fuel and oxide uranium fuel is presented. It allows to identify and explain several characteristic temperature features of the accident dynamics at the Fukushima Daiichi Nuclear Power Plant Unit 3, where one third of the reactor fuel load was MOX-fuel. [ABSTRACT FROM AUTHOR]

The paper reviews the recent progress in the description of isospin-symmetry breaking within the nuclear shell model and applications to actual problems related to the structure and decay of exotic neutron-deficient nuclei and nuclei along the N = Z line, where N is the neutron number and Z the atomic number. The review recalls the fundamentals of the isospin formalism for two-nucleon and many-nucleon systems, including quantum numbers, the spectrum's structure and selection rules for weak and electromagnetic transitions; and at the end, summarizes experimental signatures of isospin-symmetry breaking effects, which motivated efforts towards the creation of a relevant theoretical framework to describe those phenomena. The main approaches to construct accurate isospin-nonconserving Hamiltonians within the shell model are briefly described and recent advances in the description of the structure and (isospin-forbidden) decay modes of neutron-deficient nuclei are highlighted. The paper reviews major implications of the developed theoretical tools to (i) the fundamental interaction studies on nuclear decays and (ii) the estimation of the rates of nuclear reactions that are important for nuclear astrophysics. The shell model is shown to be one of the most suitable approaches to describing isospin-symmetry breaking in nuclear states at low energies. Further efforts in extending and refining the description to larger model spaces, and in developing first-principle theories to deal with isospin-symmetry breaking in many-nucleon systems, seem to be indispensable steps towards our better understanding of nuclear properties in the precision era. [ABSTRACT FROM AUTHOR]

In China Fusion Engineering Testing Reactor research, the neutronics experiment is essential in validating the neutronics codes and tools used in a blanket. Reduction activation ferritic–martensitic steel is the main structural material of the water-cooled ceramic breeder blanket, of which the main composition is Fe. However, the activation reaction of 54Fe(n, p)54Mn will bring the long half-life product of 54Mn. Therefore, the reaction rate of the reaction channel 54Fe(n, p)54Mn was investigated with accuracy in this paper. In a fusion reactor, neutron is generated not only from deuterium tritium reaction but also from the deuterium deuterium (DD) reaction. The spontaneous neutron source, $3 \times 10^{8}$ n/s 252Cf, was used to simulate DD neutron field. After irradiated for about 5 days, the activated Fe foil was measured by a high-resolution gamma-ray spectrometer with a high-purity germanium detector. The neutron flux was calculated using a Monte Carlo transport code and Fusion Evaluated Neutron Data Library (FENDL) 3.0 Files. The neutron group cross section was processed by NJOY. The relative error between the calculated value and the experimental value is less than 7%. The error of the database EAF2010 is the smallest in this paper. The self-shielding factor has a greater impact on FENDL 3.0 database. [ABSTRACT FROM AUTHOR]

There exists the following paradigm: for interaction potentials U(r) that are negative and go to zero as r goes to infinity, bound states may exist only for the negative total energy E. For E > 0 and for E = 0, bound states are considered to be impossible, both in classical and quantum mechanics. In the present paper we break this paradigm. Namely, we demonstrate the existence of bound states of E = 0 in neutron–neutron systems and in neutron–muon systems, specifically when the magnetic moments of the two particles in the pair are parallel to each other. As particular examples, we calculate the root-mean-square size of the bound states of these systems for the values of the lowest admissible values of the angular momentum, and show that it exceeds the neutron radius by an order of magnitude. We also estimate the average kinetic energy and demonstrate that it is nonrelativistic. The corresponding bound states of E = 0 may be called "neutronium" (for the neutron–neutron systems) and "neutron–muonic atoms" (for the neutron–muon systems). We also point out that this physical system possesses higher-than-geometric (i.e., algebraic) symmetry, leading to the approximate conservation of the square of the angular momentum, despite the geometric symmetry being axial. We use this fact for facilitating analytical and numerical calculations. [ABSTRACT FROM AUTHOR]

Soil moisture measurements at the field scale are highly beneficial for different hydrological applications including the validation of space-borne soil moisture products, landscape water budgeting or multi-criteria calibration of rainfall-runoff models from field to catchment scale. Many of these applications require information on soil water dynamics in deeper soil layers. Cosmic-ray neutron sensing (CRNS) allows for non-invasive monitoring of field-scale soil moisture across several hectares around the instrument but only for the first few tens of centimeters of the soil. Simple depth-extrapolation approaches often used in remote sensing applications may be used to estimate soil moisture in deeper layers based on the near-surface soil moisture information. However, most approaches require a site-specific calibration using depth-profiles of in-situ soil moisture data, which are often not available. The physically-based soil moisture analytical relationship SMAR is usually also calibrated to sensor data, but could be applied without calibration if all its parameters were known. However, in particular its water loss parameter is difficult to estimate. In this paper, we introduce and test a simple modification of the SMAR model to estimate the water loss in the second layer based on soil physical parameters and the surface soil moisture time series. We apply the model at a forest site with sandy soils with and without calibration. Comparing the model results against in-situ reference measurements down to depths of 450 cm shows that the SMAR models both with and without modification do not capture the observed soil moisture dynamics well. The performance of the SMAR models nevertheless meets a previously used benchmark RMSE of ≤ 0.06 cm3 cm−3 in both, calibrated and uncalibrated scenarios. Only with effective parameters in a non-physical range, a better model performance could be achieved. Different transfer functions to derive surface soil moisture from CRNS do not translate into markedly different results of the depth-extrapolated soil moisture time series simulated with SMAR. However, a more accurate estimation of the sensitive measurement depth of the CRNS improved the soil moisture estimates in the second layer. Despite the fact that the soil moisture dynamics are not well represented at our study site using physically reasonable parameters, the modified SMAR model may provide valuable first estimates of soil moisture in a deeper soil layer derived from surface measurements based on stationary and roving CRNS as well as remote sensing products where in-situ data for calibration are not available. [ABSTRACT FROM AUTHOR]

Cosmic-ray neutron sensing (CRNS) has emerged as a reliable method for soil moisture and snow estimation. However, the applicability of this method beyond research has been limited due to, among others, the use of relatively large and expensive sensors. This paper presents the tests conducted on a new scintillator-based sensor especially designed to jointly measure neutron counts, muons and total gamma rays. The neutron signal is first compared against two conventional gas-tube-based CRNS sensors at two locations. The estimated soil moisture is further assessed at four agricultural sites, based on gravimetric soil moisture collected within the sensor footprint. Muon fluxes are compared to the incoming neutron variability measured at a neutron monitoring station and total gammas counts are compared to the signal detected by a gamma ray spectrometer. The results show that the neutron dynamic detected by the new scintillator-based CRNS sensor is well in agreement with conventional CRNS sensors. The derived soil moisture also agreed well with the gravimetric soil moisture measurements. The muons and the total gamma rays simultaneously detected by the sensor show promising features to account for the incoming variability and for discriminating irrigation and precipitation events, respectively. Further experiments and analyses should be conducted, however, to better understand the accuracy and the added value of these additional data for soil moisture estimation. Overall, the new scintillator design shows to be a valid and compact alternative to conventional CRNS sensors for non-invasive soil moisture monitoring and to open the path to a wide range of applications. [ABSTRACT FROM AUTHOR]

In this paper, we get the nuclear mass-density parameter of known mass and known charge radius by using the AME2020 nuclear mass database and the CR2013 nuclear charge radius database. For the nuclei with N ≥ 2 1 , we obtained an empirical formula of the constant parameter equal to 0 for the difference of nuclear mass-density parameter between two neighboring isotope. That is, the nuclear mass-density parameter of the two neighboring isotopes was equal. By using this empirical formula combined with AME2020 and CR2013 databases, the calculated value of 625 nuclear charge radii was obtained. The root-mean-square deviation (RMSD) of nuclear charge radius that we have successfully obtained is σ = 0. 0 1 1 fm. In addition, one of the corrections is the neutron factor. This correction is the key improvement which reduces the RMSD to 0.0077 fm. Considering the neutron shell effect, the different shell ranges were divided into two categories for correction, and the RMSD was reduced to 0.0056 fm. Based on the revised empirical formula combined with the AME2020 database, the calculated and predicted values of nuclear charge radius were obtained with high accuracy. Some of these predictions are also very consistent with experimental values measured in recent years. In addition, we use BP neural network to study the difference of nuclear mass-density parameter on the basis of two categories. The RMSDs obtained are 0.0028 fm and 0.0038 fm, respectively. It can be seen that such a division has a certain degree of reliability and feasibility. These results show that the new relation proposed in this paper has simplicity and reliability, which can be compared with other local nuclear charge radius relations. [ABSTRACT FROM AUTHOR]

In this paper, a regression model between neutron star crust–core pressure and the symmetry energy characteristics was estimated using the Akaike information criterion and the adjusted coefficient of determination R a d j 2 . The most probable value of the transition density, which should characterize the crust–core environment of the sought physical neutron star model, was determined based on the obtained regression function. An anti-correlation was found between this transition density and the main characteristic of the symmetry energy, i.e., its slope L. [ABSTRACT FROM AUTHOR]

This paper reports on the development of stable tumor-specific gold nanoparticles (AuNPs) activated by neutron irradiation as a therapeutic option for the treatment of cancer with high tumor angiogenesis. The AuNPs were designed with different mono- or dithiol-ligands and decorated with different amounts of Arg-Gly-Asp (RGD) peptides as a tumor-targeting vector for αvβ3 integrin, which is overexpressed in tissues with high tumor angiogenesis. The AuNPs were evaluated for avidity in vitro and showed favorable properties with respect to tumor cell accumulation. Furthermore, the therapeutic properties of the [198Au]AuNPs were evaluated in vitro on U87MG cells in terms of cell survival, suggesting that these [198Au]AuNPs are a useful basis for future therapeutic concepts. [ABSTRACT FROM AUTHOR]

The ITER plasma position reflectometry system will be used to estimate the distance between the position of the magnetic separatrix and the first wall at four predefined locations, complementing the magnetic diagnostics system. The antennas of the system studied in this paper are to be installed between the blanket shield modules of rows 3 and 4, on the high-field side of the tokamak. As the antennas and part of the corresponding waveguides will be directly exposed to the plasma, they will be subjected to high radiation doses from neutrons and gammas, which may cause irradiation-induced changes in the material properties and compromise the integrity of the components. In this paper, the Monte Carlo simulation code MCNP6 and the most up-to-date ITER reference neutronics model were used to estimate the thermal loads in the system. The results, complemented with a finite-element analysis performed with ANSYS Mechanical, show that the nuclear heat loads, combined with the thermal radiation coming from the plasma, translate into operation temperatures that reach 480 °C at the tips of the antennas, slightly above the maximum recommended temperature of operation of stainless steel for ITER in-vessel components under irradiation (450 °C). Further, thermal analyses and design iterations are therefore required to improve the thermal and mechanical behavior of the system. [ABSTRACT FROM AUTHOR]

This paper presents a shutdown dose rate (SDR) calculation to estimate a newly developed preliminary concept of the equatorial port model for the Korean fusion demonstration reactor (K-DEMO). The equatorial port model was designed to provide effective radiation shielding abilities adopting the port shielding block and labyrinth structure, which was integrated into the modified K-DEMO neutronic analysis model by the Monte Carlo automatic modeling system. A rigorous two-step method was applied to couple transport (MCNP) and activation (FISPACT) codes according to three steps of calculation procedures. The results of neutron flux and decay gamma transport calculation for the equatorial port area have been indicated in this paper. The SDR calculation result near the equatorial port area reveals that a dose level in the equatorial port interspace was below $100~\mu $ Sv/h after 12 days of the shutdown. Shielding blocks and two labyrinth structures prove that they effectively attenuate neutrons on the current concept of the equatorial port model. [ABSTRACT FROM AUTHOR]

According to Internationa Thermonuclear Experimental Reactor (ITER) integration procurement arrangements, the installment of diagnostics in a port should not increase the shutdown dose rate (SDDR) in the port interspace area by no more than \sim50~\muSv/h above the baseline, assuming another 50 \muSv/h is attributed to contribution from the port structure and other ITER in-vessel components, such that the upper SDDR limit of 100 \muSv/h is not exceeded 10^6~s after shutdown. It was found that placing the initial design of the motional stark effect (MSE) and the charge exchange recombination spectroscopy (CXRS) in the equatorial port #3 resulted in an increase in the SDDR that far exceeded the limit. When we follow the optimization process discussed in this paper, substantial reduction in the port interspace SDDR was achieved. The results of this paper show that even when we combine the optimized CXRS and MSE diagnostics with a third glow discharge diagnostic, the excess of the SDDR over the baseline value did not exceed the allowed upper limit. This paper is based on utilizing the 3-D CAD-based ATTILA code for assessing the SDDR. [ABSTRACT FROM PUBLISHER]

The paper describes the construction of the neutron imaging facility at the very low-power research reactor VR-1. The training reactor VR-1 is operated by the Czech Technical University in Prague, Czech Republic. It is mainly used for the education of students in the field of nuclear engineering as well as for the training of professionals. Neutron imaging is the new field of VR-1 reactor utilisation currently under development. Extremely low reactor power at the level of 100 W brought many challenges that were necessary to overcome to build and commission a sustainable neutron radiography facility. The paper describes the reactor's neutron flux verification and the basic concept and design of the neutron imaging instrumentation. The first experimental results were mainly dedicated to testing the detection system for different radial beam port configurations, different L/D ratios, and different exposure times. Preliminary results of neutron radiography and tomography measurements at VR-1 clearly showed the potential of using neutron imaging in low-power reactors such as the VR-1 reactor. [ABSTRACT FROM AUTHOR]

The covariance committee of CSEWG (Cross Section Evaluation Working Group) established templates of expected measurement uncertainties for neutron-induced total, (n,γ), neutron-induced charged-particle, and (n,xn) reaction cross sections as well as prompt fission neutron spectra, average prompt and total fission neutron multiplicities, and fission yields. Templates provide a list of what uncertainty sources are expected for each measurement type and observable, and suggest typical ranges of these uncertainties and correlations based on a survey of experimental data, associated literature, and feedback from experimenters. Information needed to faithfully include the experimental data in the nuclear-data evaluation process is also provided. These templates could assist (a) experimenters and EXFOR compilers in delivering more complete uncertainties and measurement information relevant for evaluations of new experimental data, and (b) evaluators in achieving a more comprehensive uncertainty quantification for evaluation purposes. This effort might ultimately lead to more realistic evaluated covariances for nuclear-data applications. In this topical issue, we cover the templates coming out of this CSEWG effort–typically, one observable per paper. This paper here prefaces this topical issue by introducing the concept and mathematical framework of templates, discussing potential use cases, and giving an example of how they can be applied (estimating missing experimental uncertainties of 235U(n,f) average prompt fission neutron multiplicities), and their impact on nuclear-data evaluations. [ABSTRACT FROM AUTHOR]

To enhance the production of short-lived isotopes, higher beam powers are sought, which require targets able to accommodate them. One such target prototype is a liquid metal target LIEBE, developed at CERN. In this paper, a simulation of the proton beam interaction with the LIEBE target is presented. Simulations were performed by a series of proton transport calculations using the MCNP Monte Carlo code. The latest LIEBE target MCNP input was created in high-fidelity geometry, and the FENDL-3.1 cross-section data library was used. Flux and dose rate maps in the LIEBE target obtained from the simulations are presented in the paper. The maximum obtained dose around the target is roughly 361 Sv/h for gamma rays and 214 Sv/h for neutrons. The 70 MeV–100 µA proton beam penetrates roughly 7 mm deep into the liquid eutectic lead–bismuth. Based on this, further required changes to the LIEBE target can be evaluated. [ABSTRACT FROM AUTHOR]

Table-top neutron/x-ray sources are of great interest for uses in neutron activation analyses, in neutron/x-ray radiography, and also in medical applications. Inertial electrostatic confinement fusion (IECF) is a multiple neutron source that can emit neutrons, protons, x rays, etc., as basic products when operated in both continuous and pulsed modes. In this work, D-D neutrons are produced in the steady-state mode using a cylindrical IECF device. The neutron production rate has been optimized by using cathodes having different dimensions and geometrical transparencies. The maximum neutron production rate is found to be approaching 10 7 n / s , using a cathode having eight grid wires and a diameter of 3 cm. The neutrons are successfully used for neutron activation analysis of materials containing explosive elements. X-ray spectrum having a wide range of photon energies (30–70 keV) has been detected from this device while operated in the continuous mode. X-ray radiography of high density objects has also been performed and reported for the first time using the cylindrical IECF source with negative polarity of the central grid in this paper. [ABSTRACT FROM AUTHOR]

The results of the thermalized flux calculation that incorporate radiative capture reactions in the presence and absence of polyethylene blocks that form an enclosure for a deuteron-deuteron (D-D) neutron generator are presented. This method can be used to measure the moderated neutron flux component in a mixture of moderated and primary neutron spectra. Using 20-cm-thick polyethylene blocks to surround a D-D neutron generator, the moderation of primary neutrons was investigated using nine indium foils. In this paper, the relationship between the moderated neutron flux and the radiative capture rates in the presence and absence of polyethylene blocks is derived. This is compared to a MCNP simulation and a calculation of modulated flux that ignore the primary neutron components. [ABSTRACT FROM AUTHOR]

We have systematically studied the level density parameter, nuclear level density and decay width of neutron and fission of superheavy nuclei. This paper is validated by comparing with available experiments for 2 3 6 U and 2 4 0 Pu. The angular dependence of level density parameter, level densities and ratio of Γ n and Γ f the thermal excitation energy (U) have been studied in the superheavy region 1 0 4 ≤ Z ≤ 1 1 8. The role of entrance channel parameter on decay width of neutron and fission has been studied both in cold and hot fusion reactions in the superheavy region 1 0 4 ≤ Z ≤ 1 1 8. Systematic variation of Γ n and Γ f is observed in both the cases. Finally, predicted Γ n / Γ tot for the synthesis of superheavy nuclei Z = 1 1 9 and 120. [ABSTRACT FROM AUTHOR]