This study focuses on noise reduction in neutron tomography, a non-destructive imaging technique with inherently low signal-to-noise ratio (SNR) due to the nature of neutron sources and detectors. This research explores the application of advanced denoising techniques, departing from iterative reconstruction methods, to improve image quality. Using a sample consisting of an aluminum cylinder filled with layers of copper balls and metal bars of various compositions, we reconstructed neutron tomography data at varying exposure times with the Filtered Backprojection (FBP) algorithm, followed by denoising using the Block Matching 4D (BM4D) algorithm. Results demonstrate that BM4D significantly enhances image quality by reducing normalized mean squared error (NMSE) and improving contrast-to-noise ratio (CNR). These findings suggest that BM4D can substantially reduce acquisition times in neutron tomography while maintaining detailed structural visibility and high image quality.

The high sensitivity of neutrons to hydrogen, together with the key role of moisture in wood utilisation, makes wood-water interactions a central topic in neutron imaging studies. However, neutron imaging alone does not enable direct quantification of dry-weight-based moisture content (MC), thereby limiting its application in moisture analysis. This study presents a combined neutron and X-ray imaging method to monitor temporal changes in wood moisture with detailed anatomical resolution. Scots pine sapwood specimens with initial MCs ranging from green state to approximately 24 %, 12 %, and 0 % were subjected to unidirectional drying or wetting under controlled relative humidity decreasing from about 85 % to 30 % at 60 degrees C. Eight specimens were imaged simultaneously, and image-registration techniques were applied to compensate for shrinkage and swelling during moisture changes. Wood was modelled as discrete layers of compact timber, water, and void space. While neutron imaging provided high sensitivity to water distribution, combining both imaging modalities enabled estimation of MC and improved anatomical visualisation. The method allows investigation of wood-water interactions across entire cross-sections down to individual growth-ring features. By enabling detailed tracking of moisture dynamics under controlled climatic conditions, the approach supports improved understanding of wood drying behaviour and moisture-related material performance.

Advancements in analyzing iron archaeological artifacts are helpful in many applications, i.e., elucidating corrosion phenomena experienced by nuclear waste repositories and lifetime prediction of still-buried objects, such as pipelines. This paper investigates the corrosion state of iron-based archaeological objects through bimodal neutron and X-ray computed tomography, SEM-EDX analysis, and Raman spectroscopy. The nail BdC2, excavated from the archaeological site Bois de Châtel in Switzerland, is used as a representative case study. The workflow, starting from securing the sample from the archaeological site, beamtime experiment parameters, and data processing steps until segmentation results validation, is described in this paper. For the segmentation validation, SEM-EDX and Raman spectroscopy analyses were performed. The K-means segmentation algorithm produced satisfying results despite a mis-segmentation of one gap space between two parts of the nails. The work described in this paper is part of a larger analytical system development that aims to enable 3D physical/geometrical reconstruction and chemical composition identification and distribution within ferrous objects via bimodal neutron and X-ray computed tomography experiments, eliminating the need for invasive characterization methods.

The observation of inner, hidden material distributions of objects with cultural heritage importance requires methods which enable a transmission of the used radiation. Because inspection with visible light is limited for non-opaque samples, only X-rays and neutrons can be used for such investigations. Alternative kinds of radiation like electrons, micro-waves are limited in the practical transmission and the required spatial resolution. Besides a retrospective of successful project, we want to present ways how to collaborate and to emphasize the importance of personal commitment and contacts with relevant people in the museum’s community. To answer the question “how to present best our results”, a library of image data is under preparation for ancient Tibetan bronze objects, studied with neutron imaging methods at the PSI facilities.

The vibrational behavior of reeds in wind instruments is highly sensitive to their moisture content, yet the underlying hydration dynamics and their relationship to ageing remain poorly understood. In this study, we employ in situ neutron radiography to visualize and quantify internal water distribution in clarinet reeds at three stages of use: pristine, broken-in, and aged. Reeds were subjected to controlled wetting durations followed by drying under ambient conditions to enable time-resolved analysis of moisture uptake and retention. Neutron imaging revealed that water preferentially accumulates in the vamp region due to longitudinally exposed vascular structures, while the stock remains largely dry. Ageing significantly reduces both water uptake and retention capacity. Pristine reeds absorbed water rapidly and uniformly, whereas aged reeds exhibited faster drying; asymmetric moisture distribution; and non-uniform swelling and shrinkage, consistent with structural fatigue. These results demonstrate how repeated use alters hydration behavior and underscore the governing role of anatomical features, such as exposed vascular bundles and parenchyma cells. This study presents the first application of neutron imaging to clarinet reeds, providing spatially resolved insight into internal moisture dynamics. The findings establish a scientific basis for understanding reed break-in and ageing, with implications for performance optimization, reed design, and maintenance practices. Moreover, this work pioneers a novel application of neutron imaging in the study of woodwind instruments, where moisture control critically influences playability and longevity.

With several upcoming sample return missions, such as the Mars Sample Return Campaign, non-destructive methods will be key to maximizing their scientific output. In this study, we demonstrate that the combination of neutron and X-ray tomography provides an important tool for the characterization of such valuable samples. These methods allow quantitative analyses of internal sample features and also provide a guide for further destructive analyses with little to no sample treatment, which maintains sample integrity, including minimizing the risk of potential contamination. Here, we present and review the results from four case studies of terrestrial impactites and meteorites along with their analytical setup. Using combined X-ray and neutron tomography, a Ni-Fe silicide spherule, that is, projectile material, was located within a Libyan Desert Glass sample and the distribution of hydrous phases was pinpointed in selected impactite samples from the Chicxulub IODP-ICDP Expedition 364 drill core and the Luizi impact structure, as well as in the Miller Range 03346 Martian meteorite. Neutron and X-ray tomography give complementary three-dimensional information about the distribution of different phases within a geologic sample. We demonstrate that these two methods can be successfully used to locate meteoritic material (i.e., from the impacting object) and hydrous components in terrestrial impactites and meteorites. This can help shed light on aqueous processes in the Solar System as well as the impact cratering process. Non-destructive methods like these will be important for up-coming sample return missions to characterize the returned samples and guide further destructive analyses. Combined neutron and X-ray imaging was used to locate projectile material and hydrous phases in meteorites and terrestrial impactites Locating and identifying projectile material can shed light on the impact cratering process Combined neutron/X-ray tomography can serve as a fundamental method for the characterization of material from (future) sample return missions

This study presents a preliminary examination of the effects of environment changes post-excavation on heavily corroded archaeological Roman iron nails using neutron tomography and image registration techniques. Roman nails were exposed to either a high relative humidity environment, or fast thermal drying as primary experiments to show the power of this imaging technique to monitor and quantify the structural changes of corroded metal artifacts. This research employed a series of pre- and post-treatment tomography acquisitions (time-series) complemented by advanced image registration methods. Based on mutual information (MI) metrics, we performed rigid body and affine image registrations to meticulously account for sample repositioning challenges and variations in imaging parameters. Using non-affine local registration results, in a second step, we detected localized expansion and shrinkage in the samples attributable to imposed environmental changes. Specifically, we observed local shrinkage on the nail that was dried, mostly in their Transformed Medium (TM), the outer layer where corrosion products are cementing soil and sand particles. Conversely, the sample subjected to high relative humidity environment exhibited localized expansion, with varying degrees of change across different regions. This work highlights the efficacy of our registration techniques in accommodating manual removal or loss of extraneous material (loosely adhering soil and TM layers around the nails) post-initial tomography, successfully capturing local structural changes with high precision. Using differential analysis on the accurately registered samples we could also detect and volumetrically quantify the variation in moisture and detect changes in active corrosion sites (ACS) in the sample. These preliminary experiments allowed us to advance and optimize the application of a neutron tomography and image registration workflow for future, more advanced experiments such as humidity fluctuations, corrosion removal through micro-blasting, dechlorination and other stabilization treatments.

Corrosion of steel reinforcement in concrete is a common degradation mechanism occurring in infrastructures worldwide. Even though extensive research has been conducted over the last decades to accurately predict the influence of steel corrosion on concrete durability, a comprehensive understanding of several micro-scale processes simultaneously involved in the corrosion mechanism is still lacking. The application of X-ray Computed Tomography (X-ray CT) can contribute to elucidate these processes, since this technique allows observing the internal status of specimens non-destructively, over time, and with a spatial resolution in the range of µm. Nevertheless, the relatively low sensitivity of light elements (e.g., hydrogen and oxygen) to X-ray CT may hinder the observation of solution within the cementitious matrix. This consideration is discussed in this letter. The results of this study show that the detection of solution in macropores (e.g., air voids) through X-ray CT is not limited by the relatively low attenuation coefficient of the fluid per se, but more by the spatial resolution at which acquisitions are performed and by the dimensions of the porous volume where solution penetrates. The observations reported in this letter may open several opportunities to further study the influence of the moisture conditions of air voids on several degradation mechanisms of reinforced cementitious materials (e.g., steel corrosion, freeze-thaw damage), which have been rarely investigated with X-ray CT according to the literature. The application of these findings could significantly deepen the understanding of several micro- scale processes that affect the durability of reinforced cementitious materials which still need to be elucidated, as further discussed in the present letter.

The steel-concrete interface (SCI) is known to play a major role in corrosion of steel in concrete, but a fundamental understanding is still lacking. One reason is that concrete's opacity complicates the study of internal processes. Here, we report on the application of bimodal X-ray and neutron microtomography as in-situ imaging techniques to elucidate the mechanism of steel corrosion in concrete. The study demonstrates that the segmentation of the specimen components of relevance - steel, cementitious matrix, aggregates, voids, corrosion products - obtained through bimodal X-ray and neutron imaging is more reliable than that based on the results of each of the two techniques separately. Further, we suggest the combination of tomographic in-situ imaging with ex-situ SEM analysis of targeted sections, selected on the basis of the segmented tomograms. These in-situ and ex-situ characterization techniques were applied to study localized corrosion in a very early stage, on reinforced concrete cores retrieved from a concrete bridge. A number of interesting observations were made. First, the acquired images revealed the formation of several corrosion sites close to each other. Second, the morphology of the corrosion pits was relatively shallow. Finally, only about half of the total 31 corrosion initiation spots were in close proximity to interfacial macroscopic air voids, and above 90 percent of the more than 160 interfacial macroscopic air voids were free from corrosion. The findings have implications for the mechanistic understanding of corrosion of steel in concrete and suggest that multimodal in-situ imaging is a valuable technique for further related studies.

We have developed neutron tomography as a new tool to study the interior of ancient works of art. The present paper details the principles of the method and summarizes also some of the latest results, particularly concerning Mongolian Buddhist statues of the 17./18th century. It is shown that offering deposits made of organic and ceramic materials, even when fully enclosed in a cast metallic statue, can be examined in a non-invasive way. Within certain limits this concerns composition, size, structure and position of the interior deposits. Such studies can contribute to understand the history of ritual practices and their goals. They can also contribute to evaluate whether a statue has been properly cleaned and filled during consecration and is therefore fit for religious service. Such studies can also help to form an opinion of whether a statue is genuine.

This article presents the methodology and initial findings of the SNSF Sinergia project CORINT. The project's objective is to elucidate the corrosion mechanisms affecting iron-based structures entrapped in various porous media. This paper focuses specifically on iron archaeological artefacts (IAAs) in soil. A novel multimodal quantitative imaging technique, which integrates neutron and X-ray computed tomography (NX-CT), is under development for non-destructive examination of corrosion processes. The method involves registering and fusing neutron and X-ray tomography data, followed by Gaussian mixture model (GMM) clustering for phase segmentation. Imaging was conducted on two IAAs, Vrac C and BdC1. Additionally, random cross-sections of these samples underwent analysis through optical microscopy, µRaman spectroscopy, and SEM-EDS to characterize and correlate corrosion layers with NX-CT results. This study yields valuable insights into the corrosion of IAAs, enabling the non-destructive investigation of corrosion processes in porous media. The implications extend beyond the preservation of cultural heritage, to the examination of long-term corrosion behaviors in contemporary iron structures, steel within concrete, and nuclear waste disposal plans.

We propose a method to analyze the characteristics of scintillator screens for neutron imaging applications. Using calculations based on the theory of cascaded linear steps as well as experimental measurements, we compared the characteristics of different lithium- and gadolinium -based scintillator screens. Our results show that, despite their much lower light output, gadolinium -based scintillators outperform lithium -based scintillators in terms of noise characteristics for a variety of imaging setups. However, the relative performance of scintillator screens is highly dependent on the other setup characteristics such as the beam spectrum, field of view, used optical lens and size of the camera sensor. Consequently, the selection of the best scintillator screen - as well as the scintillator characteristics assessment in new developments - requires a systematic consideration of all these elements, as enabled by the framework presented here.

The present study aims to analyze the processes at play when wood is exposed to liquid water, focusing on transport on growth ring and cellular scales and using two imaging modalities: neutron radiography and X-ray tomography images (obtained respectively at Neutra SINQ and Tomcat SLS at PSI, Villigen, Switzerland). Neutron imaging is used to characterize liquid water transport at growth ring scale in the three directions of the wood (longitudinal, radial and tangential). Based on neutron measurements, we determine unsaturated permeability of spruce and pine as function of moisture content. X-ray tomography enables us to dynamically visualize the flow of liquid water at wood cellular level, showing involved structures and to identify concomitant deformations due to water adsorption. Documenting both transport and deformation can provide a path for insightful characterization and accurate quantification of water transport in wood. Based on measurements, we will determine unsaturated permeability of spruce and pine as function of moisture content. The multi-scale methodology - cellular to growth ring scales - ensures a characterization of the hygromechanical behavior of this hierarchical material.

This paper presents the analysis of particle-laden liquid metal flow around a cylindrical obstacle at different obstacle Reynolds numbers. Particles in liquid metal are imaged using dynamic neutron radiography. We present the results of particle tracking velocimetry of the obstacle wake flow and demonstrate the capabilities to assess both temporal and spatial characteristics of turbulent liquid metal flow, validating our methods against theoretical expectations, numerical simulations and experiments reported in the literature. We obtain the expected linear vortex shedding frequency scaling with the obstacle Reynolds number and correctly identify the universal algebraic growth laws predicted and observed for trajectory curvature in isotropic homogeneous two-dimensional turbulence. To our knowledge, this is the first such result for liquid metals. Particle residence times within the obstacle wake and velocity statistics are also derived and found to be physically sound. Finally, we outline potential improvements to our methodology and plan for further research using neutron imaging of particle-laden flow.

Neutron imaging is a non-destructive testing method that functions according to principles similar to X-ray imaging. In contrast to X-rays, neutrons can generally penetrate metals rather well, but at the same time they have a high sensitivity for hydrogen. This makes neutron imaging – which includes radiography (investigations in 2D) as well as tomography (3D) – an ideal method for studying the impact of playing historical brass instruments. Playing a brass instrument creates an accumulation of moisture inside the instrument, which can eventually lead to the generation and expansion of corroded areas inside it. This moisture, along with many other products of corrosion, contains hydrogen, which provides a high degree of contrast for neutron imaging. This article explains how neutron imaging was used to monitor the condition of historical brass instruments, i.e. the changes in the internal corroded areas, by comparing 3D CT-data sets acquired before and after the instruments had been played on a regular basis over the period of fourteen months.