Abstract The detection of illicit cargo and hazardous materials within global logistics systems has become a high-security priority due to increasing and diversifying contraband. While modern X-ray and millimeter-wave imaging systems offer excellent throughput and structural visualization for inspection, they face inherent limitations in elemental identification and penetration through high-density cargo. Alternatively, neutron interrogation, which utilizes uncharged particles for inspection, exhibits superior penetration power compared to the other techniques and provides the elemental composition of subject materials through nuclear reactions. This article provides a comprehensive review of neutron-based active interrogation technologies developed over the past three decades for security screening. They are categorized into thermal neutron analysis, pulsed fast neutron analysis, the associated particle technique, and others, based on their physical principles and detectable signatures. Significant research initiatives from the United States, Europe, and Australia are examined, highlighting the transition from laboratory-scale proof-of-concept studies to field-deployable systems. This article discusses technical issues regarding detection sensitivity, inspection times, throughput, and spatial footprint required for radiation safety. Complementary technologies, such as photon interrogation with photoneutrons or nuclear resonance fluorescence, are also reviewed as potential solutions to these constraints. This article presents a perspective on the future evolution of technologies aimed at enhancing the reliability and feasibility of active interrogation in real-world security environments.
Dispersive double reflections realized by means of two bent perfect crystal (BPC) slabs of different cuts used as a sandwich can provide a monochromatic beam of excellent resolution parameters. The dispersive sandwich monochromator/analyzer provides the freedom to combine crystal slabs of different cuts, that is, different crystal reflections for the double diffraction process. For some combination of the individual crystal slab, it is possible to achieve the back-scattering resolution for a rather low monochromator take-off angle. Therefore, by using a suitable combination of two slabs, one can practically obtain a monochromatic neutron beam of any wavelength in the thermal region. Depending on the bending radius of the sandwich the resolution Δλ/λ and the Δ α collimation can be continuously adjusted in the range of 5 × 10 −5 –1 × 10 −3 . Such dispersive BPC elements can also be used for the high-resolution analysis of the scattered beam, as well as for the high-precision λ-calibration of the time-of-flight neutron scattering devices. Another advantage of this dispersive monochromator realization is saving one axis of the neutron scattering instrument.
Accurate calculation of the neutron scattering function for light water from theoretical model is often limited due to the challenges associated with the incoherent and inelastic correction of hydrogen. Traditional correction methods rely on empirical formulas, which lack generality and accuracy. Although quantum correction methods for light water have been studied for a while, they have not yet been translated into practical, openly available tools for calculating the scattering function S ( Q , omega ) . In this paper, we present an open-source computational tool that provides a stable numerical implementation of the Gaussian approximation-assisted quantum correction (GAAQC) framework for light water. The tool applies quantum corrections to classical neutron scattering data derived from molecular dynamics (MD) simulations. It takes two inputs-both obtainable from standard MD trajectories: (a) the vibrational density of states (VDOS) and (b) the classical scattering function S cl ( Q , omega ) -and outputs the quantum-corrected scattering function S ( Q , omega ) . Our implementation overcomes the instabilities that previously limited the GAAQC method, enabling reliable calculation over a wide dynamic range of momentum and energy transfer.
Modern electronic systems are typically highly integrated, structurally complex, and multilayered. During their operational lifecycle, some of these systems inevitably encounter neutron environments, which can lead to their functional failures or equipment damage. To validate their resilience against neutron irradiation, accelerated neutron irradiation tests are generally required. In this study, a multimethod approach was developed to quantify the modulation of the atmospheric neutron beam. Specifically, the neutron modulation induced by multilayered printed circuit boards (PCBs) was measured at the Atmospheric Neutron Irradiation Spectrometer (ANIS) for the first time. Bismuth (Bi) activation foils, a time-of-flight diamond detector, and an static random access memory (SRAM) monitor were used, respectively. The neutron flux decreases by more than 25% for six-layer PCBs across most of the neutron energy range. Monte Carlo simulations were also conducted and compared with the experimental data. This study can help researchers calibrate the experimental results when conducting accelerated neutron irradiation tests at ANIS.
Larmor diffraction (LD) is a neutron scattering technique that offers enhanced resolution by harnessing the Larmor precession of neutron spins in a magnetic field. By encoding subtle changes in neutron momentum transfer into significant alterations in the Larmor phase of neutron spins, LD can be employed to measure lattice expansion, lattice distortion, and mosaicity with exceptional resolution. As originally proposed by Rekveldt et al., LD necessitates the magnetic field boundaries to be tilted to be parallel to the crystal plane of interest. This report explores the fundamental principles shared between LD and spin-echo small-angle neutron scattering (SESANS). Drawing inspiration from the flexibility of SESANS to adjust magnetic field boundaries to optimize the resolution in the measurement of the neutron momentum transfers q , we will demonstrate that the strict requirement of parallel alignment between the magnetic field boundaries and the crystal plane can be relaxed for the measurements of mosaicity. Such relaxation will expand the accessible diffraction angles for these situations that are highly constrained.
The interrogation of materials with X-rays or neutrons to determine structure, energetics, and dynamics is fundamental to advancing physical and chemical materials science and enabling innovative material technologies. A persistent challenge in materials development is that progress depends on understanding structure and dynamics across multiple length and time scales in increasingly complex, multicomponent systems featuring interfaces, heterogeneity, and hierarchical organization. Despite rapidly growing demands on materials characterization, current experimental approaches are almost exclusively based on isolated X-ray or neutron scattering and spectroscopy, reflecting a paradigm largely unchanged for decades. To assess the scientific need for a new experimental paradigm, a 3-day workshop sponsored by the U.S. National Science Foundation (NSF) was held at the SpringHill Suites, San Jose, California, from June 2 to 4, 2022. The workshop brought together 70 national and international experts who critically evaluated opportunities enabled by concurrent neutron and X-ray (NeX) scattering, spectroscopy, and imaging experiments. The participants reached a clear consensus that establishing NeX capabilities is crucial for advancing the science of complex materials in the United States. This report illustrates the scientific drivers for NeX experiments through representative examples spanning biomaterials, energy materials, soft matter, nanomaterials, quantum materials, geoscience, and applied materials research. The complementarity of neutrons and X-rays is essential for robust model development and refinement, particularly in multiphase and multicomponent systems. While joint refinement of data from separate experiments is valuable, concurrent measurements uniquely eliminate uncertainties arising from sample evolution, environmental drift, and irreproducibility associated with experiments performed at different locations and times. Realizing NeX capabilities will require the development of new instrumentation, data analysis frameworks, and robust sample environments compatible with both neutron and X-ray probes. Addressing these challenges will enable unambiguous interpretation of complex materials behavior and open new frontiers in materials research.
In recent years there has been a renewed interest in the development of compact neutron sources, as an alternative to large facilities based on reactor or accelerator installations. In fact, compact accelerator-driven neutron sources (CANS) have been in operation for a long time, but different circumstances have recently prompted the design and development of new high-intensity CANS projects around the world. The compact character of such installations must be also reflected in their target-moderator-reflector (TMR) systems, where the significant radiation fields they are immersed in and the requirement of optimized configuration to achieve the expected high neutron fluxes, pose new challenges for the design of the appropriate TMR in each case. In this work, some conceptual ideas are presented that can be considered as initial guesses for the necessary simulation work, with particular emphasis on moderator configurations able to supply thermal, cold, and very cold neutron beams based on high-intensity CANS or medium-intensity CANS. To pursue this endeavor a special effort was made to collect analytical tools and experimental information in support of the proposed concepts.
We have previously reported on a systematic underestimation of uncertainties by the error-propagation mechanism in neutron-scattering data-reduction software. The problem arises in one-to-many operations that apply a single term across multiple data points, such as normalization of detector counts to a neutron monitor spectrum. While we were able to compute the correct uncertainties for a number of concrete data-reduction workflows, the solution was not necessarily generalizable and could not be applied in interactive data analysis with an a priori unknown data-reduction workflow. In this contribution, we derive upper bounds for the correct uncertainties in workflows involving such one-to-many operations. The bounds are simple and fast to compute and can be applied on the fly during data-reduction.
In this work, we present the development of small-angle scattering components in McStas that describe the neutron interaction with 70 different form and structure factors. We describe the considerations taken into account for the generation of these components, such as the incorporation of polydispersity and orientational distribution effects in the Monte Carlo simulation. These models can be parallelized by means of multi-core simulations and graphical processing units. The acceleration schemes for the aforementioned models are benchmarked, and the resulting performance is presented. This allows the estimation of computation times in high-throughput virtual experiments. The presented work enables the generation of large datasets of virtual experiments that can be explored and used by machine learning algorithms.
The International Collaboration on Advanced Neutron Sources (ICANS) is an informal network of laboratories gathering scientists and engineers involved in the development of pulsed neutron sources and accelerator-based spallation neutron sources.The collaboration was founded in 1977 as a forum to promote discussions and collaborative work, and to share information on three main topics: accelerators, targets and moderators, and instruments.The 24th meeting of this network (ICANS XXIV) was held from the 29th October to the 3rd November 2023 in Dongguan, Guangdong Province, China.Sponsored by the China Spallation Neutron Source 1 (CSNS), a largescale scientific infrastructure constructed and operated by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS), ICANS XXIV has attracted more than 200 participants from France, Germany, Japan, Russia, UK, USA, Switzerland and China (Fig. 1).Over 90 abstracts were submitted for presentations and posters.Extensive discussions took place during the conference on the following subjects: accelerator, targets and moderators, neutron and muon instruments (including Fig. 1.
The increasing demand for long wavelength neutrons is being motivated by the need to study larger objects and slower motions characterizing the new materials related to the requirements of nowadays science and technology. However, not much work has been done so far towards the identification of materials and conditions able to produce a copious flux of very cold neutrons (VCN) at either stationary or pulsed sources. This work presents the results of a preliminary study aimed at exploring materials that look promising as potential moderators for VCN sources. For this purpose, a search is done for the existence of very low energy excitations in the generalized density of states of some molecular systems, which can be efficient to slow down already cold neutrons by exchanging energy with them. Besides reviewing and improving the available information on methane (II) and methane clathrate, it is found that such objective can be realized by the quantum dynamics corresponding to the librations of the methyl groups in the methyl fluoride and the p-xylene molecules encapsulated in two different molecular hosts at low temperatures.
At the second stage of China Spallation Neutron Source (CSNS-II), it is predicted that 2 PB raw experimental data will be produced annually from twenty instruments. Scientific computing puts forward higher requirements for data sharing, utilization, retrieval, analysis efficiency, and security. However, the existing data management system (DMS) based on ICAT has several limitations including poor scalability of metadata database, imperfect data-management lifecycle and inflexible API. To ensure the accuracy, usability, scalability and efficiency of CSNS-II experimental data, a new scientific data management system is therefore designed based on the DOMAS framework developed by the Computing Center of IHEP. The data acquisition, transmission, storage and service systems are re-designed and tailored specifically for CSNS-II. Upon its completion, the new DMS will overcome the existing challenges and offer functions such as online display, search functionality and rapid download capabilities for metadata, raw data and analyzed data; flexible and user-friendly authorization; and data lifecycle management. Ultimately, the implementation of the new Data Management System (DMS) is expected to enhance the efficiency of experimental data analysis, propelling CSNS-II to achieve international advanced standards. Furthermore, it aims to reinforce self-reliance and technological strength in the field of science and technology at a high level in China. The development and deployment of the new DMS begin at the end of 2023.
The linac and the 3 GeV rapid-cycling synchrotron (RCS) at the Japan Proton Accelerator Research Complex (J-PARC) were designed to provide 1-MW proton beams to the following facilities. Due to the improvement of the accelerator system, we accelerated a 1-MW beam with a small beam loss. The lack of anode current in the radiofrequency (RF) cavity, rather than beam loss, limits the RCS beam power. Recently, we developed a new acceleration cavity that can accelerate a beam with a low anode current. This new cavity enables us to reduce the requirement for the anode power supply and accelerate a beam of more than 1 MW. We considered how to achieve beam acceleration beyond 1 MW. So far, a beam of up to 1.5 MW is expected to be accelerated after replacing the RF cavity. We also studied to achieve an up to 2 MW beam in J-PARC RCS.
Presented three-axis neutron diffractometer performance documents the feasibility of using it in special cases high-resolution powder diffraction studies, namely, for elastic and plastic deformation studies of bulk polycrystalline samples when the whole powder diffraction spectrum is not required. Contrary to the conventional double-axis setting the suggested alternative consists of an unconventional three axis set-up employing a bent perfect crystal (BPC) monochromator and analyzer with a polycrystalline sample in between. The analysis of the profile of the beam diffracted by a sample is carried out by rocking the BPC-analyzer and the neutron signal is registered by a point detector. Though the diffractometer alternative is, for measurements, much more time consuming, its resolution is, however, substantially higher and permits also plastic deformation studies on the basis of analysis of the sample diffraction profiles. The so-called analyzer rocking curve then provides a sample diffraction profile and could reflect the lattice or structural changes. Moreover, much larger widths (up to 10 mm) of the irradiated gauge volumes can be investigated when just slightly affecting the resolution of the experimental setting.
We investigated neutron flux at a sample position and energy resolution of a direct-geometry disk-chopper spectrometer AMATERAS under various chopper conditions and compared them with simulations and calculations. The measured flux was comparable to that of similar high-flux spectrometers. The resolution when using a pulse-shaping chopper correlated well with the analytical calculations, including the thickness of the disk chopper, the sample size, and the penetration depth into the detector. The results show that the chopper, placed at the intermediate distance of the primary spectrometer, functions as a pulse shaper that optimizes the flux and resolution below the incident energy of 10 meV.
We have been developing nanosized graphene, called graphene flower, as a material that induces coherent scattering very cold neutrons. Previous experiments have found that the seed part of the graphene flower is more effective than the petal part in increasing the coherent scattering. Based on these results, we found that further modification of the graphene flower to increase the seed portion increased the total cross-section, although it did not reach the level of nanodiamonds.
A new design of spallation target has been installed and operated at the first target station of the ISIS Neutron and Muon Source (ISIS TS-1), as part of the recently completed “TS-1 Project”. Detailed Finite Element Analysis (FEA) simulations were used to guide the design process and predict target performance. Since the TS-1 Project target began operation in November 2022, operating data has been collected and used to validate the target simulation approach. Measured temperatures of 9 out of 10 target plates showed good agreement with FEA simulations of both steady-state and transient behaviour. However, the front target plate temperature was elevated compared to predictions. Because the installed target was now too radioactive to permit hands-on inspection, FEA simulations became an indispensable tool to understand the possible causes and safety implications of this anomalous behaviour. The anomalous elevated temperature appears to be highly localised; a combination of simulations and experiments indicates the mostly likely cause is poor thermal contact between the thermocouple and the bulk of the target plate. In all other respects the target is operating as predicted, and is running reliably at up to 120 kW.
We conduct simulations of Spin Echo Small Angle Neutron Scattering (SESANS) by employing Monte Carlo methods to a setup using four magnetic Wollaston prisms. Our primary focus involves the validation of these models, encompassing monochromatic scenarios across various neutron wavelengths to ascertain the reliability of the simulations. Subsequently, we extend this validation to encompass simulations in time-of-flight mode. Our model consistently and precisely predicts the scattering patterns emanating from dilute spheres in both monochromatic and time-of-flight modes. Notably, it also accurately reproduces the intricate encoding associated with scattering occurring between the third and fourth magnetic Wollaston prism, which provides us with another approach to increase the solid angle coverage of a SESANS instrument. This validation process conclusively demonstrates the efficacy of our simulation methods. Importantly, it paves the way for simulating more intricate and realistic instrumental configurations, broadening the horizons for future research endeavours.
The development of detectors for the European Spallation Source is an important parallel element to the effort put into the design and construction of the neutron source and instruments. The 10Boron-film-based detector developments that started over a decade ago as basic detector concepts have now reached technical maturity after intense prototyping work and numerous testing campaigns. Several of the ESS beamlines that will soon enter the commissioning phase started welcoming the detector systems built with the 10B-film converter technology. The real-size demonstrators evolved in the last 2–3 years into a diverse suite of gas proportional counters for use in diffraction, reflectometry and small-angle scattering studies in spite of the operational complexity posed by the requirements for large-area coverage, low material budget and robustness for operation in the high-flux and high-radiation environment of ESS. The detectors are now being shipped to ESS or undergoing the last performance and calibration tests before being handed over to the instrument teams for installation in the host beamlines. A common feature of these detector systems is the very large number of readout channels that they are instrumented with in order to fulfill the demanding requirements for sensitivity, spatial resolution and count-rate capability. Across all of the detector types that will operate at ESS, the integration, testing and commissioning of the read-out technologies and software tools for data reduction, calibration and analysis are the focus of the detector and integration teams. These will yield a wealth of knowledge about their operation as well as initial results on the in-situ performance, a very important asset to ensure rapid commissioning of the detectors when neutrons from the ESS source become available. In this paper we will give an overview of the 10B-film-based detector technologies included in the ESS detector suite that are currently facing the transition from the production phase to installation and integration with the other beamline components, which comes with its own specific challenges of both organizational and technical nature.
We have designed and realized a temperature and pressure controlled cell for Neutron Reflectometry (NR) and Small Angle Neutron Scattering (SANS) that is compatible with simultaneous optical transmission and resistivity measurements. The cell can accommodate samples up to 102 mm (4 inch) in diameter, can be pressurized from vacuum up to 10 bar gas pressure and the sample temperature can be controlled up to 350°C. The four single crystal quartz windows ensure both a good neutron and optical transmission and hence can be used in combination with in-situ optical transmission measurements. We present the cell and illustrate its performance with a series of neutron reflectometry experiments performed on Ta based thin films under a hydrogen containing atmosphere.
