Neutron-based Methods Research Articles

X-ray and neutron imaging for cultural heritage: the INFN-CHNet experience

This paper reports on the instrumentation and expertise developed within the INFN-CHNet network for X-ray and neutron imaging, which enable non-invasive identification of materials and production processes in the field of cultural heritage. INFN-CHNet is the network of the Italian National Institute of Nuclear Physics specifically dedicated to the development and application of scientific methods and technologies to cultural heritage. This article focuses on portable MA-XRF scanners, often complemented by additional techniques, PIXE imaging on a newly developed portable accelerator, X-ray radiography and tomography, exploited to their full potential also through the use of portable systems, and neutron radiography and tomography, which require large-scale facilities. In many respects, the information obtained from X-ray and neutron-based methods is complementary, facilitating a comprehensive characterisation of materials, structures, and manufacturing techniques.Graphical abstract

Non-destructive analysis of Pb-acid battery positive plates, based on neutron tomography

Notwithstanding the in-depth understanding of lead-acid battery degradation processes developed in a time-honored field of science, there is still wide scope for knowledge-based technological advancements, in particular, targeting positive plate (PP) durability. Non-destructive imaging of the internal morphology, structure and chemistry of these components, enabled by neutron-based methods, is capable of disclosing otherwise inaccessible observables, that can form the factual basis for new pathways to device improvement. In this study, we propose a post mortem investigation of as-formed and electrochemically aged PPs, centered on neutron tomography and complemented by x-ray radiography and scanning-electron microscopy. These complementary imaging methods, thriving on different contrast mechanisms, allow 2D/3D position-sensitive morphological analyses of the nature and evolution of the positive active material (PAM) and of the spines of the PP, including: morphology variation, crack location, porosity distribution and identification of hydrogenated compounds. Specifically, in this work, we have pinpointed the differences in degradation modes—resulting from the application of a standard ageing protocol—of PPs fabricated in two technologically alternative ways: punching and gravity-casting, showing the superiority of the formed in terms of electrode stability upon charging abuse conditions.

Lithium and Electrolyte Distribution in 18650-Type Lithium-Ion Batteries

Extensive cycling of lithium-ion batteries leads to a partial loss of their capacity due to various side effects like formation of the solid-electrolyte-interface (SEI), loss of active lithium, drying out of the cell [1, 2] etc. Typical profiles of side reactions, instantaneous temperature[3] and current density[4] are non-uniform, which leads to a heterogeneous lithium distribution in the battery. The loss of lithium inventory is typically correlated with the formation of SEI during cycling, whereas the quantitative role of the electrolyte in the cell operation and cell fatigue remains not fully understood yet.Primarily, this is related to the fact that quantification of the liquid electrolyte in an electrically and environmentally isolated system such as lithium-ion batteries is not a simple task. Opening the system would inhibit changes of its state, e.g. evaporation of electrolyte. Typical X-ray or neutron-based methods utilized in non-destructive cell characterization are not capable to quantify the amount of liquid electrolyte with desired accuracy. Recently it has been shown that liquid electrolyte (DMC-based) exhibit a long range order, when frozen at T<260 K [5]. This long range order can be detected by neutron diffraction and the amount of frozen electrolyte can be quantified. Furthermore, applying spatially-resolved neutron powder diffraction (Ref. [6]) pave the way for the simultaneous quantification of lithium amount in graphite and relative concentration of frozen electrolyte (Figure 1).The aim of the current study is a non-destructive quantification of lithium and electrolyte, their spatial distribution throughout the cell and concentration changes vs. cell fatigue. Combined experimental studies embedding electrochemistry, X-ray computed tomography, and neutron diffraction is applied for 18650-type cylinder cell based on NCA|C chemistry, where high-resolution neutron diffraction independently reveals a direct correlation between losses of active lithium in the graphite anode and those of liquid electrolyte (both volume-averaged). The 3D lithium distribution is probed by spatially resolved neutron powder diffraction, thereby displaying the non-trivial character of active lithium/electrolyte losses and complex profile of the cell capacity fading.[1] D. Petz, M.J. Mühlbauer, V. Baran, M. Frost, A. Schökel, C. Paulmann, Y. Chen, D. Garcés, A. Senyshyn, Journal of Power Sources 2020, 448, 227466.[2] B. Ziv, V. Borgel, D. Aurbach, J.-H. Kim, X. Xiao, B.R. Powell, Journal of The Electrochemical Society 2014, 161, A1672-A1680.[3] H. Dai, B. Jiang, X. Wei, Energies 2018, 11,[4] S.V. Erhard, P.J. Osswald, P. Keil, E. Höffer, M. Haug, A. Noel, J. Wilhelm, B. Rieger, K. Schmidt, S. Kosch, F.M. Kindermann, F. Spingler, H. Kloust, T. Thoennessen, A. Rheinfeld, A. Jossen, Journal of The Electrochemical Society 2017, 164, A6324-A6333.[5] A. Senyshyn, M.J. Mühlbauer, O. Dolotko, H. Ehrenberg, Journal of Power Sources 2015, 282, 235-240.[6] A. Senyshyn, M.J. Mühlbauer, O. Dolotko, M. Hofmann, H. Ehrenberg, Scientific Reports 2015, 5, 18380. Figure 1

Neutron analyses of eight Bronze Age swords from Austria: The question of ‘stabbing’ or ‘cut-and-thrust’ weapons

European Bronze Age swords are rare finds; they cannot normally be sampled in the destructive manner that would be necessary to assess their manufacturing technique, or to obtain evidence regarding their use primarily as ‘stabbing’ or ‘slashing’ weapons. Therefore, non-invasive neutron-based methods are potentially ideal. In this paper, neutron diffraction (ND) and Neutron Resonance Capture Analyses (NRCA) are presented. The analyses were undertaken on eight Bronze Age metal-hilted swords of various types, from three Austrian museums. Neutron diffraction measurements were carried out on all eight swords at the ISIS Neutron Facility, STFC Rutherford Appleton Laboratory (UK), giving information about crystallographic microstructure, and major metal alloy and mineral compound proportions. NRCA was carried out on four of the swords at the European Commission’s Joint Research Centre (JRC) in Geel (BE), to determine the elemental compositions at various regions of these swords, because no invasive sampling was permitted. X-ray fluorescence spectroscopy (XRF) was used to measure the elemental compositions of four swords from which one sample each was permitted to be cut for metallographic examination. The tin contents of the swords determined by NRCA, XRF and neutron diffraction data are in good agreement; some small differences could be well understood. Questions about the use of these swords as primarily either ‘stabbing’, or ‘cut-and-thrust’ weapons were addressed based on the neutron diffraction results and provide information which will be especially relevant for experimental archaeology and use-wear analysis.

Neutrons for Cultural Heritage-Techniques, Sensors, and Detection.

Advances in research in Cultural Heritage see increasing application of a multidisciplinary approach and the combined use of physical and chemical characterization of artefacts that can be used to define their structure and their state of conservation, also providing valuable information in selecting the most suitable microclimatic conditions for the exhibition environment. This approach provides a platform for a synergic collaboration amongst researchers, restorers, conservators, and archaeologists. Existing state-of-the-art technologies for neutron-based methods are currently being applied to the study of objects of historical and cultural interest in several neutron-beam facilities around the world. Such techniques are non-invasive and non-destructive and are, therefore, ideal to provide structural information about artefacts, such as their composition, presence of alterations due to the environmental conditions, inclusions, structure of the bulk, manufacturing techniques, and elemental composition, which provide an overall fingerprint of the object’s characteristics, thanks to the nature of the interaction of neutrons with matter. Here, we present an overview of the main neutron methods for the characterization of materials of interest in Cultural Heritage and we provide a brief introduction to the sensors and detectors that are used in this framework. We conclude with some case studies underlining the impact of these applications in different archaeological and historical contexts.

Advanced Postirradiation Characterization of Nuclear Fuels Using Pulsed Neutrons

Methods for postirradiation characterization of bulk (cm3) irradiated materials or even spent nuclear fuels are sparse due to their extremely radioactive nature. While several methods exist to characterize smaller volumes (< 1 mm3) of such samples, selecting these volumes from larger samples is challenging. X-ray-based methods are prohibitive due to the strong γ-radiation from the sample flooding the detectors. Neutron-based methods available in the proximity of irradiation reactors allow for thermal neutron radiography or computed tomography using a small reactor source, but one cannot assess isotope distributions or microstructural features such as phases, texture, or strain from diffraction measurements due to flux limitations. We present herein a pathway to provide pulsed neutron characterization of bulk irradiated samples using time-of-flight neutron diffraction for microstructural characterization and energy-resolved neutron imaging for assessment of isotopic densities and distributions. Ultimately, laser-driven pulsed neutron sources may allow deployment of these techniques pool-side at irradiation reactors.

Analysis of 14-MeV neutron induced gamma-ray spectra using multiwavelets

Neutron-based methods of bulk material analysis are used to detect contraband in cargo, characterize coal and cement, and identify unexploded ordnance, among other applications. Characteristic gamma rays produced in nuclear reactions (inelastic neutron scattering, thermal neutron capture, and activation) initiated by 14-MeV neutrons in the volume of an irradiated object are utilized for its elemental identification. In many situations, automated methods of spectral analysis and decision analytics are required. In this study, a spectrum analysis technique based on wavelets was developed, which determines elemental intensities using peak areas corresponding to characteristic photons. The algorithm was evaluated using experimental data measured with a 14-MeV pulse neutron source and high-resolution and low-resolution photon detectors. It was shown that this technique provides quick, accurate, and objective analysis of gamma-ray spectra.

Non-destructive analyses of bronze artefacts from Bronze Age Hungary using neutron-based methods

Our paper produces results on production techniques of prehistoric metal artefacts using non-destructive neutron-based methods, considering aspects of heritage protection.

From 2-D to 3-D to 4-D electron microscopy: an outline of the essence and promise of unconventional crystallography and spectroscopy

After outlining his debt to, and indirect contact with, W.L. Bragg, who was his predecessor-but-one as Director of the Royal Institution, the author first outlines how the simplest of 2-D electron microscopic techniques – the gold decoration method of Betghe – was used to determine point-defect (vacancies) and line defect (screw dislocations) concentrations in layered solids such as graphite. There follows an illustrative summary of the various modes of utilizing 3-D electron microscopy that encompasses electron crystallography, electron energy-loss spectroscopy and electron tomography. These shed light on the structural and morphological features of solids, and they reveal in exceptional detail, often at sub-unit cell level, both regular and irregular intergrowths. In contrast to X-ray or neutron-based methods of structural elucidation, which produce structural features averaged over as many as 1014 unit cells, 3-D electron microscopy probes as little as 103 or so unit cells. It also enables the visualization of numerous features through direct imaging. Finally, the essence of 4-D electron microscopy is adumbrated. Here, the time-domain (down to the femtosecond level) is added to the 3-D spatial ones, thereby promising, and already providing, unprecedented insights into the dynamics of change within, and at, the surfaces of solids.

Overview: Formation Evaluation (May 2007)

Realistically, only a limited number of measurements can be made in a borehole. Most logs function by stimulating the formation with some form of energy and recording how it responds. Some of the best analytical techniques use beams of charged particles, but putting a particle accelerator downhole is impractical, and we must make do with electrically neutral forms like electromagnetic radiation, neutrons, and sound waves. Neutrinos are electrically neutral, but because they need a swimming pool full of ozone-destroying chemicals as a detector, prospects for their use are not good. Of the sensible sources of energy that have been exploited, electromagnetic radiation appears in the greatest range of devices and frequencies (e.g., resistivity, nuclear magnetic resonance, the density log, and some casing-inspection devices). Neutron-based methods can provide a lot of data about rocks and fluids, although somehow they never seem to get the acclaim they deserve. That leaves sonic logs. At its simplest, this tool was the easiest to understand: create a sonic pulse at one end of the tool and measure the time it takes to travel a known distance along the borehole. At the other extreme, a full-wave field explanation of how the tool works is best left to the specialist. The first tools appeared 50 years ago and used a single monopole transmitter and two receivers to measure formation velocity. Normally, this arrangement provides a reliable measurement of compressional velocity, and it is still used throughout the former Soviet Union. The business end of these early tools was approximately 5 ft long; the latest models are significantly longer but are superficially similar. Like automobiles, however, the big changes are under the bonnet ("hood" if you prefer). The latest models use an array of approximately 10 receiver stations. Each station consists of 8 individual receivers arranged azimuthally around the tool axis—an increase from 2 to approximately 100 receivers in 50 years. The number of transmitters also has increased, and, more importantly, the simple monopole source has been joined by dipole, quadrapole, and even a miniature vibroseis source. This technology comes at a high price in both operating charges and the volume of data generated (of the order of gigabytes for 1000 m of logged interval). The incentive for this exponential increase in complexity is that of all the log types, the sonic has proved most versatile. The sonic log started its life as the link from well to seismic section and/or a porosity tool. Now, it is increasingly used as a way to characterize the stress field, quantify anisotropy, and, hence, to help design development wells that are less prone to failure. An excellent example of old technology evolving to answer modern problems. Formation Evaluation additional reading available at the SPE eLibrary: www.spe.org SPE 100353 "Multiscale Pore Structure Characterization by Combining Image Analysis and Mercury Porosimetry" by H. Han, University of Waterloo, et al. SPE 102435 "NMR Petrophysics in Thin Sand-Shale Laminations" by C.C. Minh, Schlumberger, et al. SPE 102175 "A New Method for Improving LWD Logging Depth" by C.R. Chia, SPE, Schlumberger, et al. Available at the OTC Library: www.otcnet.org OTC 18199 "Controlled Source Electromagnetic Imaging in Areas of Complex Geology" by L.M. MacGregor, OHM Ltd., et al.

Multiplexed gas Cherenkov detector for reaction-history measurements

A diagnostic is being designed for the National Ignition Facility, using fusion gamma rays to measure highly time-resolved bang times and deuterium-tritium (d-t) interaction rates for imploding inertial fusion capsules. As a complement to neutron-based methods, gas Cherenkov detectors were chosen for this purpose because of proven ultrahigh bandwidth, thresholding versatility, and minimal time-of-flight dispersion. Gas Cherenkov detector prototypes, involving streak cameras and fast photomultiplier, microchannel plate detectors, are being tested using d-t implosions at the Omega Laser Facility. The possibility of simultaneous streak camera and photomultiplier, microchannel plate recordings of a source in one gas Cherenkov detector instrument is advantageous for reasons of independent measurement and extended reaction-history coverage. A multiplexed gas Cherenkov detector system was demonstrated successfully using electron pulses produced by the Idaho State University linear electron accelerator. A reaction-history diagnostic scheme composed of several types of detectors is proposed. The detectors considered reflect current and improving technology that allows coverage over a significant range of a reaction history generated from National Ignition Facility implosions.

Investigations on landmine detection by neutron-based techniques

Principles and techniques of some neutron-based methods used to identify the antipersonnel landmines (APMs) are discussed. New results have been achieved in the field of neutron reflection, transmission, scattering and reaction techniques. Some conclusions are as follows: The neutron hand-held detector is suitable for the observation of anomaly caused by a DLM2-like sample in different soils with a scanning speed of 1 m 2/1.5 min; the reflection cross section of thermal neutrons rendered the determination of equivalent thickness of different soil components possible; a simple method was developed for the determination of the thermal neutron flux perturbation factor needed for multi-elemental analysis of bulky samples; unfolded spectra of elastically backscattered neutrons using broad-spectrum sources render the identification of APMs possible; the knowledge of leakage spectra of different source neutrons is indispensable for the determination of the differential and integrated reaction rates and through it the dimension of the interrogated volume; the precise determination of the C/O atom fraction requires the investigations on the angular distribution of the 6.13 MeV gamma-ray emitted in the 16O(n,n′ γ) reaction. These results, in addition to the identification of landmines, render the improvement of the non-intrusive neutron methods possible.

Observation of high-energy deuterium–tritium fusion gamma rays using gas Cherenkov detectors

As fusion ignition conditions are approached using the National Ignition Facility (NIF), independent high-bandwidth gamma-ray fusion-burn measurements become essential complements to neutron-based methods. Time resolution ∼20 ps (10–30 GHz), energy discrimination, and significant stand off distance may be needed for credible burn history measurements. The 16.75 MeV gamma rays that accompany deuterium–tritium (d+t) fusion provide a high-bandwidth alternative to 14 MeV fusion neutrons for d+t burn-history measurements. A thresholding detector, based on the Cherenkov effect, resulting from Compton and pair production electron interactions in gaseous carbon dioxide, offers a means of separating the high-energy fusion gamma rays from other background sources. When coupled to appropriate streak camera recorders, a gas Cherenkov system response of 15 GHz is feasible. As a first step toward this goal, a gas Cherenkov system, employing a 1 GHz photodiode detector, was fielded at the Omega laser facility to demonstrate unambiguous detection of fusion gamma rays from high-yield d+t implosions. With the carbon dioxide Cherenkov production threshold at 12 MeV, the observed high-energy gamma-ray signal is proportional to the observed 14 MeV fusion neutron yield and independent of neutron-induced gamma rays.

Where is high resolution electron microscopy taking us?

Recent advances in electron microscopy have opened up exciting new possibilities for examination of the fine structure of matter. Whereas X-ray or neutron-based methods give structures averaged out over about 10 18 unit cells, high resolution electron microscopy can reduce this to some 10 4 unit cells. It is, as it were, now possible to study local variations in the terrain instead of the landscape as a whole. These local variations may represent regions of chemical constitution and activity different from those of the main structure.