Differentiating minerals using high-resolution X-ray tomography (µCT) relies on distinct differences in the attenuation coefficient µ. The µ value depends on an interplay between the material density ρ and the effective atomic number Zeff of a mineral phase. Difficulties in identifying mineral phases arise when this interplay gives similar µ values and thus limited contrast within µCT images. Untangling these two dependencies is essential to improve the three-dimensional chemical identification of critical minerals. Lab-based methods and techniques often incorporate different measures, but only show a limited application potential on multiphase geological samples. Using high-Z spectral laboratory-based µCT we studied the potential of directly identifying chemical elements within the practical margins of high-Z spectral detectors. This paper compares the results from three mineral deposits using two spectral µCT setups. Chemical elements with a Z higher than molybdenum and a concentration of at least some weight percentage were correctly identified using K-edge imaging. The suitability of the different high-Z spectral detectors depends largely on the availability of prior knowledge of the sample composition. Quantifying elemental concentrations is element- and sample specific and currently does not allow for optimal automated mineralogy solutions. Improving the three-dimensional identification of minerals can be achieved with dedicated analyses of the energy-dependent µ curve and therefore will remain the focus of future work.

X-ray ptychography is a robust microscopy technique with nanoscale resolution that requires a spatially and temporally coherent illumination. In a typical setup, the temporal coherence requirements are satisfied by monochromating the x-ray source, e.g., using a crystal monochromator. Recent studies have shown that energy resolving, or hyperspectral, detectors can to some extent replace the role of the monochromator to perform, e.g., edge-subtraction ptychographic imaging with broadband radiation in a single acquisition. Scaling this capability from two dimensions (2D) to three dimensions (3D), and from a single absorption edge to multiple edges, is critical for its applications in structural and elemental characterisation. The method is hitherto limited by the inherently lower maximum count rate of hyperspectral detectors and the chromaticity of the optics often used in x-ray ptychography experiments, namely Fresnel zone plates. In this work, we design an optimized broadband spectroscopic ptychography setup and use it to perform 3D hyperspectral imaging of particles of battery material containing various percentages of nickel, manganese, cobalt (NMC). We show that we can identify different compositions based on their spectral response. We discuss the results and provide guidelines for future exploitation of the method in laboratory settings.

A 100-nm-thick gadolinium layer deposited on a pixelated silicon sensor was activated in a neutron field to measure the internal conversion electron (ICE) spectrum generated by neutron capture products of 155Gd and 157Gd. The experiment was performed at the ISIS neutron and muon facility, using a bespoke version of the HEXITEC spectroscopic imaging camera. Signals originating from internal conversion electrons, Auger electrons, x rays and gamma rays up to 150 keV were identified. The ICE spectrum has an energy resolution of 1.8-1.9 keV at 72 keV and shows peaks from the K, L, M, N+ ICEs of the 79.51 keV and 88.967 keV 2+-0+ gamma transitions from the first excited states in 158Gd and 156Gd, respectively, as well as the K ICEs of the 4+-2+ transitions at 181.931 keV and 199.213 keV from the respective second excited states. Spectrum analysis was performed using a convolution of a Gaussian with exponential functions at the low and high energy side as the peak shaping function. Relative ICE intensities were derived from the fitted peak areas and compared with internal conversion coefficient (ICC) values calculated from the BrIcc database. Relative to the dominant L shell contribution, the K ICE intensity conforms to BrIcc and the M, N, O+ ICE intensities are somewhat higher than expected.

Increasing electrode thickness is gaining more attention as a potential route to increase energy density for Li ion batteries although the realizable capacity and rate capability are usually limited by Li+ ion diffusion during (dis)charge, especially at increased (dis)charge rates. It remains challenging to visualize and quantify the low atomic number Li+ chemical stoichiometry distribution inside the electrode within commercially standard battery geometry, e.g. coin cells with stainless steel casings. Here, we map the distribution of Li + chemical stoichiometry in the electrode microstructure inside a working coin cell battery to show the amount of electrode materials contributing to energy storage performance using innovative in situ correlative full -field X-ray Compton scattering imaging (XCS-I) and X-ray computed tomography (XCT). We design and fabricate an ultra-thick (-1 mm) cathode of LiNi0.8Mn0.1Co0.1O2 with a microstructure containing vertically oriented pore arrays using a directional ice templating method. This novel technique paves a new way to map low atomic number elements in 3D structures and study how the microstructure improves Li + ion diffusivity and energy storage performance.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The performance of Li+ ion batteries (LIBs) is hindered by steep Li+ ion concentration gradients in the electrodes. Although thick electrodes (≥300 µm) have the potential for reducing the proportion of inactive components inside LIBs and increasing battery energy density, the Li+ ion concentration gradient problem is exacerbated. Most understanding of Li+ ion diffusion in the electrodes is based on computational modeling because of the low atomic number (Z) of Li. There are few experimental methods to visualize Li+ ion concentration distribution of the electrode within a battery of typical configurations, for example, coin cells with stainless steel casing. Here, for the first time, an interrupted in situ correlative imaging technique is developed, combining novel, full-field X-ray Compton scattering imaging with X-ray computed tomography that allows 3D pixel-by-pixel mapping of both Li+ stoichiometry and electrode microstructure of a LiNi0.8 Mn0.1 Co0.1 O2 cathode to correlate the chemical and physical properties of the electrode inside a working coin cell battery. An electrode microstructure containing vertically oriented pore arrays and a density gradient is fabricated. It is shown how the designed electrode microstructure improves Li+ ion diffusivity, homogenizes Li+ ion concentration through the ultra-thick electrode (1 mm), and improves utilization of electrode active materials.

HEXITEC is a spectroscopic imaging X-ray detector technology developed at the STFC Rutherford Appleton Laboratory for X-ray and γ-ray spectroscopic imaging applications. Each module has 80 × 80 pixels on a 250 μm pixel pitch, and has been implemented successfully in a number of applications. This paper presents the HEXITEC 2 × 2 detector system, a tiled array of 4 HEXITEC modules read out simultaneously, which provides an active area of 16 cm 2 . Systems have been produced using 1 mm thick Cadmium Telluride (CdTe) and 2 mm thick Cadmium Zinc Telluride (CdZnTe) sensor material. In this paper the system and data processing methods are presented, and the performance of the systems are evaluated. The detectors were energy calibrated using an 241 Am sealed source. Three types of charge sharing correction were applied to the data-charge sharing addition (CSA), charge sharing discrimination (CSD), and energy curve correction (ECC) which compensates for energy lost in the inter-pixel region. ECC recovers an additional 34 % of counts in the 59.5 keV peak in CdTe compared to the use of CSD; an important improvement for photon-starved applications. Due to the high frame rate of the camera system (6.3 kHz) an additional End of Frame (EOF) correction was also applied to 6.0 % of events to correct for signals that were readout whilst the signal was still forming. After correction, both detector materials were found to have excellent spectroscopic performance with a mean energy resolution (FWHM) of 1.17 keV and 1.16 keV for CdZnTe and CdTe respectively. These results successfully demonstrate the ability to construct tiled arrays of HEXITEC modules to provide larger imaging areas.

Larger field of view hybrid photon counting detectors are commonly constructed using multiple distinct sensor tiles, keeping costs and process yields within reasonable parameters. It is however practically impossible to make these multiple tiles form one gapless active detection surface, especially if uniformly sized pixels are desired. While multiple existing techniques and technologies aim at either reducing the size of these gaps or filling in missing information using various algorithms, some tiling artefacts are hard to avoid without other drawbacks or high device costs. A novel technique, WiggleCam, has been developed by the authors to fill any inactive regions (due to tiles or faulty pixels) with real measured photons using precise movement of the sensors. This technique completely removes tiling artefacts with no overhead placed on the user. While this technique has been successfully demonstrated using a HEXITEC 2x2 camera[1] mounted on an external movement stage, further refinement and mechanical miniaturisation is required for applied use. In parallel to this, the SpeXIDAQ[2] software framework for hyperspectral X-ray cameras has been developed at Ghent University. In order to benefit maximally from both the WiggleCam technique and the SpeXIDAQ framework, a custom designed readout platform is being designed, incorporating six HEXITEC ASICs in a 2x3 tiled array setup. By opting for a 10 Gbps fibre connection, the full 9kHz design framerate can be transferred and processed simultaneously for all six ASICs, an improvement over the 6.3kHz limit of the USB3 connection used in the existing HEXITEC 2x2 readout. Moving the WiggleCam motion system into the camera itself reduces the amount of mass that needs to be moved, and increases the precision of the system as a whole. It also makes for a much more compact camera system, able to be mounted at beamlines and lab facilities the same way a conventional photon counting camera would be. Additionally, this readout platform serves as a testbed for on-FPGA processing and compression techniques to be developed in tandem with the SpeXIDAQ framework. This hardware-assisted processing of hyperspectral X-ray camera data will greatly benefit the implementation of readout systems for future much higher bandwidth hyperspectral ASICs, which will see single sensor output rates approaching 100 Gbps. Any reduction of the required output bandwidth and off-camera processing power would be favourable for applications of these next-generation ASICs, if cheaper data transfer technologies and processing hardware can be considered without loss of performance. [1] Wilson, Matthew D., et al. “Multiple module pixelated CdTe spectroscopic X-ray detector” IEEE Transactions on nuclear science 60.2 (2013): 1197-1200 [2] Van Assche, Frederic, et al. “The Spectral X-ray Imaging Data Acquisition (SpeXIDAQ) Framework” Sensors 21(2) (2021): 563 The authors acknowledge funding from the Industrial Research Fund under grant F2020/IOF-StarTT/135, and thank STFC for providing the HEXITEC materials and information used in the development of this work.

In order to keep down costs and control yields, large area hybrid detectors are commonly implemented using multiple sensor tiles in various geometries. Due to the presence of guard rings, readout connections and other design considerations it is practically impossible to make tiled sensor arrays where the tiles meet up exactly. Even in the case of four side buttable sensors, arrays will still have some measure of dead space between the tiles. A variety of hardware and software techniques currently exist to fill in the inactive space, such as roof tile arrangements of sensor tiles, software interpolation to fill in gaps, and stitching together multiple overlapping but shifted exposures. All of these techniques present their own drawbacks, from greatly increasing hardware complexity, introducing undesirable artefacts in certain applications, or increasing measurement times and experimental overhead. The authors propose a novel technique, called WiggleCam, for mitigating inactive regions and malfunctioning pixels in X-ray cameras which use very high frame rates (often exceeding 1 kHz). This is commonly the case in hyperspectral imagers, which provide raw ADC output frames at very high time resolution for energy dispersive single photon detection. In this work we present the results of a proof-of-concept implementation of the method using a HEXITEC 2x2 camera[1] mounted on an XY-stage, with all data processing done using SpeXIDAQ, the in-house developed framework for hyperspectral imagers[2]. A practical implementation requires access to the raw high-framerate camera output before it is integrated into the final exposure. By moving the detector such that every section of the region of interest is imaged at least part of the desired exposure time, and shifting the individual photon events using the coincident detector position in the lab frame before integration, any inactive areas are fully covered. By then compensating for the non-uniform exposure time no deterministic motion path is required, and a final image output is obtained free from gaps, without temporal overhead, and with no further post-processing required by the end-user. The method is shown to accurately compensate for the inter-tile gaps without compromising the spatial and spectral resolution. It also provides a way to increase the effective spatial resolution without physically reducing the pixel pitch. This presentation will conclude by demonstrating a new camera device under development using multiple HEXITEC sensors, designed to include the Wigglecam method in the camera construction itself for a more compact and useful implementation. [1] Wilson, Matthew D., et al. “Multiple module pixelated CdTe spectroscopic X-ray detector” IEEE Transactions on nuclear science 60.2 (2013): 1197-1200 [2] Van Assche, Frederic, et al. “The Spectral X-ray Imaging Data Acquisition (SpeXIDAQ) Framework” Sensors 21(2) (2021): 563 The authors acknowledge funding from the Research Foundation Flanders (FWO) under grant G0A0417N, the Industrial Research Fund under grant F2020/IOF-StarTT/135, and thank STFC for providing the HEXITEC system used in the development of this work.

Photon counting X-ray imagers have found their way into the mainstream scientific community in recent years, and have become important components in many scientific setups. These camera systems are in active development, with output data rates increasing significantly with every new generation of devices. A different class of PCD (Photon Counting Detector) devices has become generally available, where camera data output is no longer a matrix of photon counts but instead direct measurements of the deposited charge per pixel in every frame, which requires significant off-camera processing. This type of PCD, called a hyperspectral X-ray camera due to its fully spectroscopic output, yet again increases the demands put on the acquisition and processing backend. Not only are bandwidth requirements increased, but the need to do extensive data processing is also introduced with these hyperspectral PCD devices. To cope with these new developments the Spectral X-ray Imaging Data Acquisition framework (SpeXIDAQ) has been developed. All aspects of the imaging pipeline are handled by the SpeXIDAQ framework: from detector control and frame grabbing, to processing, storage and live visualisation during experiments.

A possible improvement on a new method of single acquisition hyperspectral (spectroscopic) ptychographic imaging, making use of a hyperspectral X-ray camera, is presented. Undulator tapering is used at the synchrotron to broaden the energy distribution of the X-ray beam to a suitable level for edge subtraction. The combination of a coherent imaging method such as ptychography with spectroscopy poses difficulties in experimental setup design regarding probe size. The final goal of the experiment, a K-edge subtraction, is not successful, but the technique is nevertheless promising. The capability of resolving the absorption edge applies to a wide range of research areas, such as element specific investigations in biological, materials, and earth sciences. We discuss the problems and their possible solutions.

X-ray ptychography has revolutionized nanoscale phase contrast imaging at large-scale synchrotron sources in recent years. We present here the first successful demonstration of the technique in a small-scale laboratory setting. An experiment was conducted with a liquid metal-jet x-ray source and a single photon-counting detector with a high spectral resolution. The experiment used a spot size of 5  μm to produce a ptychographic phase image of a Siemens star test pattern with a submicron spatial resolution. The result and methodology presented show how high-resolution phase contrast imaging can now be performed at small-scale laboratory sources worldwide.

Multilayer monochromator devices are commonly used at (imaging) beamlines of synchrotron facilities to shape the X-ray beam to relatively small bandwidth and high intensity. However, stripe artefacts are often observed and can deteriorate the image quality. Although the intensity distribution of these artefacts has been described in the literature, their spectral distribution is currently unknown. To assess the spatio-spectral properties of the monochromated X-ray beam, the direct beam has been measured for the first time using a hyperspectral X-ray detector. The results show a large number of spectral features with different spatial distributions for a [Ru, B4C] strip monochromator, associated primarily with the higher-order harmonics of the undulator and monochromator. It is found that their relative contributions are sufficiently low to avoid an influence on the imaging data. The [V, B4C] strip suppresses these high-order harmonics even more than the former, yet at the cost of reduced efficiency.

We present a new method of single acquisition spectroscopic imaging with high spatial resolution. The technique is based on the combination of polychromatic synchrotron radiation and ptychographic imaging with a recently developed energy discriminating detector. We demonstrate the feasibility with a Ni-Cu test sample recorded at I13-1 of the Diamond Light Source, UK. The two elements can be clearly distinguished and the Ni absorption edge is identified. The results prove the feasibility of obtaining high-resolution structural and chemical images within a single acquisition using a polychromatic X-ray beam. The capability of resolving the absorption edge applies to a wide range of research areas, such as magnetic domains imaging and element specific investigations in biological, materials, and earth sciences. The method utilises the full available radiation spectrum and is therefore well suited for broadband radiation sources.

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Hyperspectral X-ray detectors, which provide the full energy spectrum detected by each individual pixel, have become available for use in lab-based facilities. The addition of spectral information currently comes at the cost of low overall acceptable flux rates, and can introduce countrate nonlinearity at higher energies. Neither of these drawbacks are desirable for transmission imaging and tomography. In this paper a new data processing software chain is presented for the SLcam, a pnCCD-based hyperspectral camera prototype, allowing for more control over the conversion from raw frames to hyperspectral images. Complementary to the processing software, a set of live data visualisations was developed to aid in monitoring ongoing experiments and to allow for preliminary data processing on-the-fly. The combination of these software elements forms the first step towards general applicability of hyperspectral imaging at laboratory tomography setups.

High-resolution X-ray computed tomography (μCT) is nowadays an established technique for material characterization. However, the technique only yields morphological information, and the composition of the object can only be retrieved based on an educated guess. On the other hand, three-dimensional highresolution X-ray fluorescence spectroscopy (μXRF) is an analytical technique that yields the chemical composition of a sample. In the past, several efforts have been made to combine both methods. Typically, they apply both techniques at different setups, and register the results [1,2]. One notable system developed earlier combines micro-CT and full-field XRF in one apparatus [3].

The present work focuses on the development of novel injectable, self-gelling composite hydrogels based on two types of low esterified amidated pectins from citrus peels and apple pomace. Sol-gelderived, calcium-rich bioactive glass (BG) fillers in a particle form are applied as delivery vehicles for the release of Ca2+ ions to induce internal gelation of pectins. Composites were prepared by a relatively simple mixing technique, using 20% w/v BG particles of two different sizes (2.5 and <45 μm). Smaller particles accelerated pectin gelation slightly faster than bigger ones, which appears to result from the higher rate of Ca2+ ion release. μCT showed inhomogeneous distribution of the BG particles within the hydrogels. All composite hydrogels exhibited strong antibacterial activity against methicilin-resistant Staphylococcus aureus. The mineralization process of pectin-BG composite hydrogels occurred upon incubation in simulated body fluid for 28 days. In vitro studies demonstrated cytocompatibility of composite hydrogels with MC3T3-E1 osteoblastic cells.

Recent advances in high resolution X-ray tomography (μCT) technology have enabled in-situ dynamic μCT imaging (4D-μCT) of time-dependent processes inside 3D structures, non-destructively and non-invasively. This paper illustrates the application of 4D-μCT for visualizing the removal of fatty liquids from kitchen sponges made of polyurethane after rinsing (absorption), squeezing (desorption) and cleaning (adding detergents). For the first time, time-dependent imaging of this type of system was established with sufficiently large contrast gradient between water (with/without detergent) and olive oil (model fat) by the application of suitable fat-sensitive X-ray contrast agents. Thus, contrasted olive oil filled sponges were rinsed and squeezed in a unique laboratory loading device with a fluid flow channel designed to fit inside a rotating gantry-based X-ray μCT system. Results suggest the use of brominated vegetable oil as a preferred contrast agent over magnetite powder for enhancing the attenuation coefficient of olive oil in a multi fluid filled kitchen sponge. The contrast agent (brominated vegetable oil) and olive oil were mixed and subsequently added on to the sponge. There was no disintegration seen in the mixture of contrast agent and olive oil during the cleaning process by detergents. The application of contrast agents also helped in accurately tracking the movement and volume changes of soils in compressed open cell structures. With the in house-built cleaning device, it was quantified that almost 99% of cleaning was possible for contrasted olive oil (brominated vegetable oil with olive oil) dispersed in the sponge. This novel approach allowed for realistic mimicking of the cleaning process and provided closer evaluation of the effectiveness of cleaning by detergents to minimize bacterial growth.

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