Neutron-based Techniques Research Articles

IAEA fostering of the development and applications of nuclear analytical techniques for Heritage Science

The IAEA Physics Section is strongly involved in the development and utilization of accelerator-based analytical techniques, which are powerful tools for the characterization of cultural and natural heritage objects and materials. Various activities are carried out with the purpose to build capacity, strengthen capabilities, transfer knowledge and foster networking in the field of heritage science. In addition, access to different X-ray fluorescence spectrometers and other analytical techniques is provided at the Nuclear Science and Instrumentation Laboratory (part of the IAEA Physics Section), and access to ion beam accelerators and synchrotron light is facilitated thanks to collaborations with Ruđer Bošković Institute (RBI) in Croatia and the Elettra Sincrotrone facility in Italy, respectively. Member States are also supported on their Research and Development programmes, as well as through the technical cooperation projects. This paper aims to provide a broad overview about how the IAEA Physics Section is engaged in the field of heritage science, promoting the safe, reliable, and effective use of ion beam, X-ray and neutron-based techniques for the characterization and preservation of cultural and natural heritage through its global networks and partners.

4-Methoxypicolinic Acid N-Oxide: One of the Shortest Hydrogen Bonds Known Characterized by Neutron Diffraction, Inelastic Neutron Scattering, Infrared Spectroscopy, and Periodic DFT Calculations.

The present work focuses on the case of an extremely short intramolecular O-H···O hydrogen bond (H-bond) found in 4-methoxypicolinic acid N-oxide (MPANO). The donor···acceptor separation of 2.403 Å makes the H-bond in MPANO one of the shortest H-bonds known. We elucidated the structure and dynamics of the H-bond by two neutron-based techniques, namely, single-crystal diffraction and inelastic scattering (INS) vibrational spectroscopy. We also utilized conventional infrared (IR) spectroscopy as well as quantum chemical computations on isolated and periodic models. Both the protiated and deuterated variants of MPANO were investigated by INS and IR. All the methods used unequivocally confirm the existence of an extremely short, asymmetric H-bond, with the proton located near yet off the midpoint. The main relevant feature of the IR spectrum is an extremely broad, complex, and red-shifted OH (OD) stretching band spanning between 1800 and 500 cm-1 and centered at about 1360 cm-1, which indicates the presence of extensive anharmonicity and coupling with other H-bond modes. Of the modes characteristic of H-bond dynamics, only the out-of-plane OH (OD) bending can clearly be detected in the INS spectra; it has a relatively high frequency indicative of the strength of the H-bond. The computed structure is in excellent agreement with the diffraction measurement when periodicity is taken into account. The calculated harmonic frequencies show a reasonable match with the observed spectral features, whereby the assignment of the IR and INS spectra is facilitated. The hydrogen stretching frequency, however, appears to be significantly overestimated, on account of the limitations of the harmonic approximation and the complex nature of the short H-bond.

Determination of moisture content in coal using pulsed fast thermal neutron activation technique

The quality of coal is greatly influenced by the residual moisture content, which in turn affects the Gross Calorific Value (GCV) by limiting the maximum energy that can be extracted from a given mass of coal. Various methods have been developed to measure this residual moisture, including gravimetric techniques, near-infrared spectroscopy, microwave, and infrared moisture meters. Amongst these, neutron-based techniques offer distinct advantages for bulk and rapid characterization, making them suitable for online monitoring. This article presents the use of a Pulsed Fast Thermal Neutron Activation technique to determine moisture content in various coal samples acquired from Indian coal mines. A 14.1 MeV D-T neutron source coupled with a Bismuth Germanate (BGO) detector and associated electronics have been used. The hydrogen content in the sample has been used as an indicator for the moisture and the technique has been calibrated with samples of known moisture content. The results obtained for the coal samples demonstrate a remarkable agreement with the findings of proximate analysis. A minimum quantity of 2% moisture by weight has been detected with a relative error of 0.4%.

Characterization of 17th century archaeological metallic statuettes using combined neutron tomography and neutron diffraction

A combination of neutron computed tomography and neutron diffraction analysis has been studied to demonstrate the efficacy of employing neutron-based methodologies to investigate brass metallic statuettes, thereby shedding light on their structural and phase characteristics, all the while obviating the need to dissect the sample physically. In order to corroborate the findings obtained from the neutron-based techniques, supplementary methodologies such as Energy Dispersive X-ray Fluorescence were employed to extract elemental information and validate the results. These preliminary findings draw attention to the potential of neutron imaging to unveil intricate information regarding the techniques and components employed by artisans of antiquity in the production of Indian brass artifacts. We were also able to discern concealed structural attributes within metallic statuettes, as well as ascertain the precise phase composition of the brass alloy, thus further enriching our understanding of manufacturing practices of brass statuettes in the 17th-century era.

An Experimental Approach to Assess Fluorine Incorporation into Disordered Rock Salt Oxide Cathodes.

Disordered rock salt oxides (DRX) have shown great promise as high-energy-density and sustainable Li-ion cathodes. While partial substitution of oxygen for fluorine in the rock salt framework has been related to increased capacity, lower charge-discharge hysteresis, and longer cycle life, fluorination is poorly characterized and controlled. This work presents a multistep method aimed at assessing fluorine incorporation into DRX cathodes, a challenging task due to the difficulty in distinguishing oxygen from fluorine using X-ray and neutron-based techniques and the presence of partially amorphous impurities in all DRX samples. This method is applied to "Li1.25Mn0.25Ti0.5O1.75F0.25" prepared by solid-state synthesis and reveals that the presence of LiF impurities in the sample and F content in the DRX phase is well below the target. Those results are used for compositional optimization, and a synthesis product with drastically reduced LiF content and a DRX stoichiometry close to the new target composition (Li1.25Mn0.225Ti0.525O1.85F0.15) is obtained, demonstrating the effectiveness of the strategy. The analytical method is also applied to "Li1.33Mn0.33Ti0.33O1.33F0.66" obtained via mechanochemical synthesis, and the results confirm that much higher fluorination levels can be achieved via ball-milling. Finally, a simple and rapid water washing procedure is developed to reduce the impurity content in as-prepared DRX samples: this procedure results in a ca. 10% increase in initial discharge capacity and a ca. 11% increase in capacity retention after 25 cycles for Li1.25Mn0.25Ti0.50O1.75F0.25. Overall, this work establishes new analytical and material processing methods that enable the development of more robust design rules for high-energy-density DRX cathodes.

Characterization of the In Vivo Deuteration of Native Phospholipids by Mass Spectrometry Yields Guidelines for Their Regiospecific Customization.

Customization of deuterated biomolecules is vital for many advanced biological experiments including neutron scattering. However, because it is challenging to control the proportion and regiospecificity of deuterium incorporation in live systems, often only two or three synthetic lipids are mixed together to form simplistic model membranes. This limits the applicability and biological accuracy of the results generated with these synthetic membranes. Despite some limited prior examination of deuterating Escherichia coli lipids in vivo, this approach has not been widely implemented. Here, an extensive mass spectrometry-based profiling of E. coli phospholipid deuteration states with several different growth media was performed, and a computational method to describe deuterium distributions with a one-number summary is introduced. The deuteration states of 36 lipid species were quantitatively profiled in 15 different growth conditions, and tandem mass spectrometry was used to reveal deuterium localization. Regressions were employed to enable the prediction of lipid deuteration for untested conditions. Small-angle neutron scattering was performed on select deuterated lipid samples, which validated the deuteration states calculated from the mass spectral data. Based on these experiments, guidelines for the design of specifically deuterated phospholipids are described. This unlocks even greater capabilities from neutron-based techniques, enabling experiments that were formerly impossible.

Perdeuterated GbpA Enables Neutron Scattering Experiments of a Lytic Polysaccharide Monooxygenase.

Lytic polysaccharide monooxygenases (LPMOs) are surface-active redox enzymes that catalyze the degradation of recalcitrant polysaccharides, making them important tools for energy production from renewable sources. In addition, LPMOs are important virulence factors for fungi, bacteria, and viruses. However, many knowledge gaps still exist regarding their catalytic mechanism and interaction with their insoluble, crystalline substrates. Moreover, conventional structural biology techniques, such as X-ray crystallography, usually do not reveal the protonation state of catalytically important residues. In contrast, neutron crystallography is highly suited to obtain this information, albeit with significant sample volume requirements and challenges associated with hydrogen's large incoherent scattering signal. We set out to demonstrate the feasibility of neutron-based techniques for LPMOs using N-acetylglucosamine-binding protein A (GbpA) from Vibrio cholerae as a target. GbpA is a multifunctional protein that is secreted by the bacteria to colonize and degrade chitin. We developed an efficient deuteration protocol, which yields >10 mg of pure 97% deuterated protein per liter expression media, which was scaled up further at international facilities. The deuterated protein retains its catalytic activity and structure, as demonstrated by small-angle X-ray and neutron scattering studies of full-length GbpA and X-ray crystal structures of its LPMO domain (to 1.1 Å resolution), setting the stage for neutron scattering experiments with its substrate chitin.

Applications of In Situ Neutron-Based Techniques in Solid-State Lithium Batteries

Solid-state lithium batteries (SSLBs) have made significant progress in recent decades in response to increasing demands for improved safety and higher energy density. Nonetheless, the current state SSLBs are not suitable for wide commercial applications. The low ionic conductivity, lithium dendrites growth, and unstable interfaces between solid electrodes and electrolytes are some of the challenges that need to be overcome. Therefore, it is critical to fully comprehend the structural information of SSLBs at a nanometer scale. Neutron-based techniques (NBTs) are sensitive to light elements (H, Li, B, N, O, etc.) and can distinguish heavy metals (e.g., Mn, Fe, Co, Ni, etc.) containing close atomic numbers or even isotopes (e.g., 1H and 2H). Therefore, NBTs are important and powerful structural and analytical tools for SSLB research and have substantially improved our understanding of these processes. To provide real-time monitoring, researchers have explored many sophisticated in situ NBTs to investigate the underlying mechanisms of SSLBs. This minireview article is primarily dedicated to the investigation of SSLBs using in situ NBTs. In addition, it illustrates the capabilities of different in situ NBTs on SSLBs by illustrating the capabilities of different techniques in recently published works. Ultimately, some perspectives for the next evolution of in situ NBTs in SSLBs are highlighted.

Preliminary Assessment of Radiolysis for the Cooling Water System in the Rotating Target of SORGENTINA-RF

The SORGENTINA-RF project aims at developing a 14 MeV fusion neutron source featuring an emission rate in the order of 5–7 × 1013 s−1. The plant relies on a metallic water-cooled rotating target and a deuterium (50%) and tritium (50%) ion beam. Beyond the main focus of medical radioisotope production, the source may represent a multi-purpose neutron facility by implementing a series of neutron-based techniques. Among the different engineering and technological issues to be addressed, the production of incondensable gases and corrosion product into the rotating target deserves a dedicated investigation. In this study, a preliminary analysis is carried out, considering the general layout of the target and the present choice of the target material.

In Operando Neutron Scattering Multiple-Scale Studies of Lithium-Ion Batteries.

Real-time observation of the electrochemical mechanistic behavior at various scales offers new insightful information to improve the performance of lithium-ion batteries (LIBs). As complementary to the X-ray-based techniques and electron microscopy-based methodologies, neutron scattering provides additional and unique advantages in materials research, owing to the different interactions with atomic nuclei. The non-Z-dependent elemental contrast, in addition to the high penetration ability and weak interaction with matters, makes neutron scattering an advanced probing tool for the in operando mechanistic studies of LIBs. The neutron-based techniques, such as neutron powder diffraction, small-angle neutron scattering, neutron reflectometry, and neutron imaging, have their distinct functionalities and characteristics regimes. These result in their scopes of application distributed in different battery components and covering the full spectrum of all aspects of LIBs. The review surveys the state-of-the-art developments of real-time investigation of the dynamic evolutions of electrochemically active compounds at various scales using neutron techniques. The atomic-scale, the mesoscopic-scale, and at the macroscopic-scale within LIBs during electrochemical functioning provide insightful information to battery researchers. The authors envision that this review will popularize the applications of neutron-based techniques in LIB studies and furnish important inspirations to battery researchers for the rational design of the new generation of LIBs.

Elemental analysis of concrete via fast neutron transmission and scattering spectrometry

We report on the development of neutron-based techniques to non-destructively measure the composition of concrete. Previous experimental studies demonstrated the viability of the unfolding technique to determine the ratio of water, sand and cement in well-characterised concrete samples from the transmitted neutron energy spectrum. In this work, we used MCNP6 simulations to demonstrate the extension of the technique to determine elemental compositions from transmitted, or scattered neutron energy spectra. In both cases, the simulated energy spectra provided a reliable method to unfold the composition of samples with known elemental ratios. The precision of the technique was limited by the statistical uncertainties of the simulated spectra, particularly for the case of scattered neutrons. The accuracy of the technique was heavily dependent on the uniqueness of each of the elemental responses, and reasonable prior knowledge of the composition. Given the promising results at this stage, future developments will include the addition of further elements to the response matrix, and experimental verification.

Neutron-based techniques for archaeometry: characterization of a Sardinian boat model

Sardinian metallurgy produced samples of high artistic and historical value. In particular, ship models are rare and unmatched examples of the mastery reached by Sardinian metallurgists and their production process deserves an in-depth analysis of all the phases involved in the making. In this work, we examined a Sardinian boat model to obtain information about its composition, microstructure and manufacturing technique. The object is a small bronze ship model that was found near the Nuraghe Colovros, located in north-east Sardinia (Italy). It was analysed by means of neutron imaging and neutron diffraction experiments at the ISIS Pulsed Neutron and Muon Source laboratory (Harwell, UK). Neutron techniques are relatively new in the field of archaeometry, but they are a very effective tool for the study of archaeological objects: they permit to survey complete artefacts, determine compositions and structures, assess the conservation status and address questions of effective use and casting techniques. This type of data can add new and different insights to existing archaeological information, especially where sampling is not permitted. The outcome of the study reveals a peculiar approach to the manufacturing of the boat model.

The neutron cross section of barite-enriched concrete for radioprotection shielding in the range 1 meV–1 keV

We present a characterization of a series of barite-enriched concrete samples at the atomic scale using neutron-based techniques. In particular, neutron transmission measurements provide the macroscopic cross section (also known as neutron removal cross section) as a function of the incident neutron energy in the range 1 meV–1 keV. In this range, where fewer experimental investigations are available in the literature, the cross section is dominated by the scattering events from hydrogen, as opposed to the fast-neutron region (MeV-energy neutrons) where capture events by Ba are more important. Moreover, below 1 eV, the cross section depends on the molecular or crystal structure of the components. For each sample, the amounts of barium and hydrogen are provided by neutron resonance capture analysis and deep inelastic neutron scattering, respectively. We find that the amounts of barium and hydrogen are correlated, with a lower amount of hydrogen in the samples with more barium, likely because of the absence of some calcium-silicon-hydrate structures, whose formation is inhibited by the presence of barite. Moreover, we quantify the non-negligible contribution to the neutron macroscopic cross section arising from water molecules loosely bound in concrete. This contribution makes the shielding performance of concrete dependent upon the humidity and temperature conditions affecting the installation. Our results provide additional guidelines for radioprotection workers to determine the optimal concentration of barite in mixed gamma/neutron radiation environments.

Lithium encapsulation in etched nuclear pores in polyethylene terephthalate

Encapsulation of lithium in ion-track etched polymer has been studied using both ion and neutron-based techniques. Latent tracks have been formed in Polyethylene terephthalate foils by irradiation with high energy Xe26 + ions. Subsequently, the latent-tracks have been developed, via chemical etching. The resulting pore shapes have been characterized by Ion Transmission Spectroscopy. From the analysis of the energy spectra of the ions transmitted through the membrane, it was possible to estimate pores' inner geometry and its evolution during etching. The etched foils were exposed to a LiCl aqueous solution and the depth distribution of Li incorporated into the pores was examined by implementing the Neutron Depth Profiling technique. The ability of the membrane to encapsulate the lithium in pores, was determined. The present study can be relevant to several applications, e.g., lithium-ion batteries and biosensors, where an in-depth knowledge of the pores' shape/size and of their trapping capability is required.

The road to a station for epithermal and thermal neutron analysis

Despite the large variety of research interests and themes motivating the current neutron research included in this collection, we have found common denominators characterising the manner in which the chosen research methodology tries to tackle the envisaged scientific questions. This article attempts to characterise those trends in current research with the aim of identifying the main mid-to-long term opportunities faced by electron-Volt neutron spectroscopy. The main realisation from this exercise is that the scientific community seems eager to combine neutron-based techniques over a broad energy range. To this end, the most natural choice seems to be to resort to neutron instruments where such capabilities are already present from the outset, with the most prominent example being the VESUVIO spectrometer at the ISIS pulsed neutron and muon source in the UK. However broad the operational basis of the existing neutron beamline infrastructure may be, progress, achievable only through further instrument upgrades, is the only way forward. The need to move forward is clearly seen within the community and is well documented by the research presented in this collection. This need for a substantial upgrade has crystallised in the form of a proposition to build a station rather than a conventional beamline, for Epithermal and Thermal Neutron Analysis station, hereafter ETNA.

Stone artefacts and neutrons - Case studies from Hungary

Many archaeometrical studies aim at identifying the provenance of various archaeological finds. For a large group of objects, e.g. for stone artefacts, the chemical composition might be characteristic for the supposed geological source. In the last 20 years, several projects on different scales have been launched, based on the non-destructive prompt-gamma activation analysis at the Budapest PGAA laboratory. Depending on the type of the raw material (such as obsidian, flint, radiolarite or metamorphic rocks), the success of the various neutron-based studies can be expected at different levels. In this paper, we demonstrate the potentials of the mostly applied neutron-based techniques through case studies.

Deuteration of human carbonic anhydrase for neutron crystallography: Cell culture media, protein thermostability, and crystallization behavior

Deuterated proteins and other bio-derived molecules are important for NMR spectroscopy, neutron reflectometry, small angle neutron scattering, and neutron protein crystallography. In the current study we optimized expression media and cell culture conditions to produce high levels of 3 different deuterated human carbonic anhydrases (hCAs). The labeled hCAs were then characterized and tested for deuterium incorporation by mass spectrometry, temperature stability, and propensity to crystallize. The results show that is possible to get very good yields (>10 mg of pure protein per liter of cell culture under deuterated conditions) and that protein solubility is unaffected at the crystallization concentrations tested. Using unlabeled carbon source and recycled heavy water, we were able to get 65–77% deuterium incorporation, sufficient for most neutron-based techniques, and in a very cost-effective way. For most deuterated proteins characterized in the literature, the solubility and thermal stability is reduced. The data reported here is consistent with these observations and it was clear that there are measurable differences between hydrogenous and deuterated versions of the same protein in Tm and how they crystallize.

Inelastic neutron scattering

The goal of the JDN22 school was to propose a progressive teaching eager to improve the expertise of students in neutron diffraction . Neutron-based techniques have indeed proved for decades to be essential tools in the investigation of condensed matter. This lecture is however concerned with inelastic neutron scattering and is thus somehow apart. In the context of this school, it should then only be considered as a brief introduction. We give simple examples along with the basics of the spectrometers, and finally useful formula for the inelastic cross sections in different situations. We strongly encourage interested readers to refer to the bibliography for more detailed information.

Disclosing mineralogical phases in medioeval iron nails by non-destructive neutron techniques

There is not only one methodology for the study of mineralogical phases in archaeological samples. In this paper, we discuss a strategy applied to ancient iron nail samples completely based on non-destructive analyses. The archaeological samples come from the archaeological site of Valle delle Forme (province of Brescia–Italy) and date back to the 1300–1400 ad. Neutron-based techniques, like time-of-flight neutron diffraction and neutron tomography, have been used to determine the mineralogical composition and the structure of nails. An independent check for the assessment of the presence of different mineralogical phases was given by Raman spectroscopy. The combination of different non-destructive techniques has provided very useful information on their chemical composition, nature of the patina and corrosion features of the nails (also in the bulk of the samples).

Characterization of European sword blades through neutron imaging techniques

In the present work, we have studied two European rapier blades, dating back to the period ranging from the Late Renaissance to the Early Modern Age (about 17th to 18th century). In order to determine variation in quality and differences in technology, a study was undertaken with the purpose to observe variations in the blade microstructure (and consequently in the construction processes). The samples, which in the present case were expendable, have been investigated, preliminarily, through standard metallography and then by means of white beam and energy-selective neutron imaging. The comparison of the results, using the two techniques, turned out to be satisfactory, with a substantial quantitative agreement of the results obtained with the two techniques, and show the complementarity of the two methods. Metallography has been considered up to now the method of choice for metal material characterization. The correspondence between the two methods, as well as the non-invasive character of the neutron-based techniques and its possibility to obtain 3D reconstruction, candidate neutron imaging as an important and quantitatively reliable technique for metal characterization.