Recent advances in propagation-based phase-contrast imaging, such as hierarchical imaging, have enabled the visualization of internal structures in large biological specimens and material samples. However, modulation-based techniques, which provide quantitative electron density information, face challenges when imaging larger objects due to stringent beam stability requirements and detector distortions. Extending the field of view of these methods is crucial for obtaining comparable quantitative results across beamlines and adapting to the smaller beam profiles of fourth-generation synchrotron sources. We introduce a novel image processing technique combining an eigenflat optimization with deformable image registration to address the challenges and enable quantitative high-resolution scans of centimeter-sized objects with multiple-micrometer resolution. We demonstrate the potential of the method by obtaining an electron density map of a rat brain sample 15 mm in diameter despite the limited horizontal field of view of 6 mm of the beamline. This showcases the technique's ability to significantly widen the range of applications of modulation-based techniques in both biological and materials science research.

The shape of the capillary produced during the welding of 1.4301 (X5CrNi18-10, AISI 304) stainless steel at a welding speed of 12 m/min using core-ring-shaped beams delivered through a multi-waveguide fiber was examined by means of synchrotron X-ray imaging. The results show that, under the range of process parameters covered here, ring beams create a temperature field which includes two hot spots which lag behind the center of the beam and are equidistant from the center line of the weld. In the case of small ring diameters these two hot spots can be close enough to the core beam that they can combine with it to create a wide capillary, the shape of which inhibits the formation of pores. When larger diameters are employed, the ring beam hot spots create a separate, secondary capillary (or capillaries) which may sporadically coalesce with the core beam capillary due to surface tension effects. When the capillaries merge, the depth of penetration of the combined capillary is reduced compared with the one created by the core alone. If the coalescence of the capillaries is sporadic then the weld stability is poor from both a porosity and a depth of penetration point of view.

The side channels that occur during percussion drilling in stainless steel with ultrafast lasers with linear or circular polarization were observed using high-speed X-ray imaging, capturing the dynamic process in real-time and thus providing primary insights into their formation dynamics. We identified two distinct phenomena directly linked to the formation of side channels: (1) deflection of the borehole tip and (2) melt-induced obstructions that alter the propagation of the laser radiation. These phenomena can occur independently of each other and strongly depend on the state of polarization. With linear polarization, the side channels consistently form in the plane perpendicular to the direction of polarization, while the side channels occur without any preferred orientation when drilling with circular polarization. Additionally, the first side channels form at greater depths when higher pulse energies are applied. This study improves our understanding of the complex interplay between the state of polarization, melt dynamics, and side channel formation. The findings provide valuable information for optimizing laser drilling processes, particularly for high-aspect-ratio hole drilling with high pulse energies, and have promising applications in precision micromachining and industrial laser processing.

In this study, laser beam welding (LBW) of gravity die-cast components made from the aluminum casting alloy EN AC-AlSi7Mg0.3 is investigated. The experiments are carried out using in situ X-ray observation with synchrotron radiation at the Deutsches Elektronen-Synchrotron (DESY), PETRA III beamline P07 EH4 in Hamburg, Germany. Phase-contrast videography is employed to investigate the keyhole dynamics in the LBW process, and the resulting weld pool ejections are visualized. In this investigation, the wavelet transform is introduced for time-resolved frequency analysis of keyhole dynamics in the welding process. First, the statistical fundamentals of the wavelet transform are presented based on the current state of the art. In preliminary studies, locally varying weldability is quantified using the position-dependent empirical probability of melt pool ejections. Melt pool ejections are classified as either stochastic or systematic. The subsequent wavelet analysis visualizes the frequency behavior of the maximum keyhole depth. This is followed by a position-dependent comparison of welds using frequency analyses based on the wavelet transform. This methodological study confirms the suitability of the wavelet transform for time-resolved frequency analysis of keyhole dynamics in LBW.

High welding speeds above 8 m/min during laser beam welding of high-alloy steel lead to spatter formation, resulting in material losses and spatter adhesion that significantly degrade seam quality. Superimposing the main laser intensity with a second laser intensity leads to a reduction of such effects, as melt flow conditions around the keyhole are influenced. In this configuration, the area hit from the superimposed laser must be notably larger than the main laser spot, in order to enlarge the melt pool on the top side. However, the basic interactions of keyhole, melt pool, and metal vapor using a superimposed intensity are largely unknown. In order to identify and understand the related effects with combined laser intensities a welding speed of 12 m/min was chosen, while through high-speed synchrotron radiation imaging visualization of keyhole behavior and melt flow characteristics by tracking tungsten carbide particles was carried out. The superimposed intensity widens the melt pool on the sheet top side, thereby increasing the cross-sectional area of the melt flow, while the keyhole geometry and its fluctuations remain comparable to those observed without superimposed intensity. This reduces the melts kinetic energy of the flow around the keyhole and finally spatter formation. Raising power of the superimposed laser intensity, the keyhole width expands over its entire depth, and a bulge on the keyhole rear wall due to vaporizing material is formed. This bulge causes fluctuations of the melt pool and leads to lateral spatter formation due to an upward directed melt flow at the keyhole walls. Therefore, in order to reduce spatter formation, the power of the superimposed intensity has to be chosen consequently in order to enhance melt pool dimensions and avoid bulging.

Modern solid-state lasers enable a continuous increase in welding speed due to higher possible laser beam powers. However, welding speeds above 8 m/min for high-alloy steels lead to altered melt flow dynamics and increased spatter formation, resulting in spatter adhesion and particularly in undercuts along the weld seam. In contrast to the cost- or time-intensive methods described in the state of the art to reduce these effects, modifying the intensity distributions appears to be a simple and effective approach that is independent of the welding direction. In particular, using a superimposed intensity allows a detailed investigation by adjusting the intensity with varying spot sizes or laser powers. Using a superimposed intensity to widen up the melt pool is especially effective in reducing the velocity of the melt flow around the keyhole and, consequently, spatter formation. However, its effect on other melt pool flows, especially the upward directed melt flow along the keyhole rear wall, remains largely unknown. To investigate these effects, high-speed synchrotron X-ray imaging in combination with tungsten carbide tracer particles was used to visualize the melt flow dynamics. Generally, two melt vortices are observed in the area behind the keyhole, one in the upper and one in the lower part of the melt pool. The backward melt flow at the melt pool bottom is unaffected by the additional energy input due to the limited penetration depth of the second laser. Furthermore, the upward directed flow along the keyhole rear wall remains unchanged. When increasing the second laser power, the keyhole widens and fluctuates at the rear wall. As a result, the upward melt flow at the rear wall is not discernible. In general, the superimposed intensity alters the melt flow behind the keyhole. However, these changes appear to be minor significant for spatter formation compared to the flow around the keyhole.

In deep-penetration laser welding, the associated vapor plume leads to an attenuation of the laser beam and deformation of the phase front. These effects dynamically modify the intensity distribution on the workpiece, resulting in significant fluctuations of the weld penetration depth. In this study, high-speed X-ray imaging was used to quantify the effect of the fluctuations of the vapor plume on the capillary depth during welding. Identical welding parameters for stainless steel (1.4301) were applied in two cases: one without a cross-jet and one with a cross-jet positioned 20 mm above the capillary to remove the plume. The results show that with a cross-jet, the capillary geometry experienced only negligible fluctuations, and its depth remained largely constant. In contrast, without a cross-jet and with increasing plume formation, the welding depth decreased significantly, occasionally leading to complete capillary collapse. These findings highlight the direct impact of the plume on the laser beam and its connection to the penetration stability and resulting welding depth.

The formation of transverse hot cracks in the weld seam limits the use of laser welding for high-strength aluminum alloys in lightweight electromobility applications. While transverse hot cracks initiate in the semisolid region, their exact location relative to the melt pool boundary and their relation to local solidification conditions and process parameters remain unclear. In this study, the formation of transverse hot cracks was investigated using in-situ synchrotron X-ray imaging. Crack initiation and propagation relative to the melt pool boundary, crack propagation rates, solidification rates, and the number of transverse cracks in the weld seam were evaluated as a function of welding speed and laser power. The results show that the average crack propagation rate corresponds to the local solidification rate along the melt pool boundary encountered during propagation. Increasing welding speed at constant weld depth increased both the crack propagation rate and the number of cracks in the weld seam. Reduced laser power at a constant welding speed resulted in higher crack propagation rates and more, but shallower, cracks. The findings advance the understanding of the mechanisms underlying transverse hot cracking and provide a basis for developing mitigation strategies.

Double-core fibers that deliver laser beams with adjustable amounts of power to the central core and the surrounding ring component of the fiber are of major interest for optimizing laser welding processes. However, the central focussed laser spot and the ring diameters are fixed by the fiber dimensions, the focusing optics, and the laser systems involved. This work investigates the influence of different ring beam diameters, with a constant central spot diameter, on the capillary dynamics and the formation of pores in the resulting welds in 1.4301 stainless steel (X5CrNi18-10, AISI 304). The different core-ring configurations were achieved using specially designed beam-shaping optics. The generation of pores during the welding process was examined by means of synchrotron X-ray imaging. The results show that different ring diameters have a profound effect on the melt pool geometry, the capillary shape and the location of the capillary collapse which gives rise to pore formation in the weld. In the examples presented here, larger ring diameters extended the melt pool in the direction of welding without contributing directly to the capillary evaporation. In this case the narrow, deep capillaries which are created by the core beam alone can bulge and collapse, trapping vapor and gas to create large pores. If, however, the ring beam has a small enough diameter, it can help to produce a wider capillary which does not trap gas and create pores in the same way. The mechanisms by which large bubbles in the melt can result in non-spherical pores in the weld are also explained.

Three-dimensional X-ray histology offers a non-invasive alternative to conventional 2D histology, enabling volumetric imaging of biological tissues without physical sectioning or chemical staining. However, the intrinsic greyscale contrast of X-ray tomography limits its biochemical specificity compared with traditional histological stains. In this study, we extend deep-learning-based virtual staining to the X-ray domain via cross-modality image translation to generate artificially stained slices directly from synchrotron radiation microtomography (µCT) scans. Using over 50 co-registered pairs of µCT and toluidine blue-stained histology from bone-implant samples, we trained a modified CycleGAN network tailored for limited paired data. Whole-slide histology images were downsampled to the CT voxel size, with on-the-fly data augmentation for patch-based training. The model incorporates pixelwise supervision and greyscale consistency losses, enabling histologically realistic colour outputs while preserving structural detail. Results outperformed Pix2Pix and standard CycleGAN baselines across metrics of structural similarity, perceptual fidelity, and peak signal-to-noise ratio. Once trained, the model can be applied to full µCT volumes to produce virtually stained 3D datasets that enhance interpretability without additional sample preparation. This work introduces virtual staining to 3D X-ray imaging, which may provide a scalable route for chemically informative, label-free tissue characterization in biomedical research.

Laser welding was carried out using a co-axial core-ring beam, with independent control of the power to the core and the ring. The welding process was observed using high-power X-rays and high-speed imaging equipment. Adjusting the relative powers of the core and the ring beams was found to have profound effects on the shape of both the capillary created and the weld melt pool. Moderate laser power densities in the ring were found to increase the top diameter of the weld pool and reduce fluctuations in the welding process. High laser power densities in the ring led to the creation of a second capillary which largely acted independently of the capillary generated by the laser power in the core. At high power densities and welding speeds the two capillaries were almost completely separated in the direction of travel.

Virtual histology using X-ray micro-computed tomography offers 3D tissue visualization, yet lacks the specificity of conventional histology, where targeted stains selectively highlight features like cell nuclei. While X-ray-compatible stains have now been developed, an unsolved challenge is the quantitative separation of their signal from the underlying tissue signal, which is essential for tissue-specific imaging. This work presents the first method enabling 3D stain mapping on a histologically relevant scale. Applied to murine kidneys stained with different hematein-lead complexes, the approach extracts molar contrast agent distributions alongside high-contrast morphology at the micrometer scale and is successfully validated against K-edge subtraction imaging. Moreover, the dual optical-X-ray properties of the stain enable direct spatial correspondence between X-ray-derived concentration maps and conventional optical histology of the same specimen, establishing a bridge between virtual and traditional histology. In summary, the proposed methodology provides tissue-specific virtual histology with objective, quantitative metrics across millimeter to centimeter-sized 3D volumes, opening pathways for immunospecific labeling and automated analysis of disease progression without physical sectioning.

This study investigates weld seam interaction and keyhole dynamics in dual-beam laser welding of CuSn6 alloy at varying inter-beam distances of 0.3 mm, 0.6 mm, and 0.9 mm. Numerical simulations are validated against experimental cross sections and high-speed synchrotron X-ray images to capture the narrow, intermediate, and wide keyhole regimes. The asymmetry in the weld seam is quantified through the average root-mean -square amplitude oscillation analysis to evaluate dynamic instability and coupling between the seams. Results show that the asymmetry decreases with an increasing inter-beam distance, while stronger asymmetry and seam coupling are observed at a small inter-beam spacing of 0.3 mm. This also reveals a significant transition from strongly coupled melt pool evolution at small beam spacing to structurally independent weld seam dynamics at larger spacing.

Laser welding of high-alloy steels leads to characteristic spatter formation at welding speeds above 8 m min-1 within the Single Wave and Elongated Keyhole regimes, which reduces seam quality due to material loss and adhering spatter. Spatter formation is strongly influenced by the melt flow dynamics, particularly by the local flow velocity and direction. Although current literature provides model-based descriptions of the upward melt flow along the keyhole rear wall and the flow around the keyhole, experimental measurements of these flow velocities are of particular interest. In this study, melt flow directions and velocities are quantified using high-speed synchrotron X-ray imaging combined with tungsten carbide particle tracking. As the welding speed increases and the process shifts from the Rosenthal to the Single Wave regime, the upward melt flow along the keyhole rear wall accelerates, resulting in the detachment of comparatively large spatter from a melt swelling behind the keyhole. At even higher welding speeds within the Elongated Keyhole regime, an enhanced flow around the keyhole promotes the detachment of multiple spatter from a single melt swelling.

Laser material processing procedures yield numerous benefits, as non-contact manipulation of the workpiece, high precision, and extensive automation capabilities. For metal joining, laser beam welding is a widely process employed in industry, for example in automotive body construction and in the production of electronic components. With the same optical setups as usually used for laser beam welding, a melt ejection can be induced in sheet metal, resulting in the formation of a cut. This enables laser remote fusion cutting (RFC) based on a ejection without the need for tools near the process zone. A comprehensive understanding of the conditions mechanisms causing the melt ejection or preventing it is yet to be achieved. In this study, in-situ observations of the process zone in RFC were performed using high-speed X-ray imaging synchrotron radiation, achieving frame rates up to 18 kHz for steel samples and 28 kHz for AlMg3 samples. features of the process zone morphology are extracted by means of image processing from the recordings, such the angle of front wall inclination or the ejection direction for different process parameters. The front wall angle for RFC is in line with an established model for the front wall angle in laser beam welding. Propagation-based phase-contrast imaging reveals the melt film at the cutting front, showing a decrease of the melt film thickness with increasing feed velocities. Melt dynamics at transitions between process states of cutting and not cutting could be observed. The temporal resolution was insufficient to capture humps in the melt film at the front wall steel samples. These were resolved for AlMg3 samples, confirming that humps at the front wall play an important role in the melt dynamics.

In this paper, we introduce a new class of projectors for 3D cone beam tomographic reconstruction. We find analytical formulas for the relationship between the voxel volume projected onto a given detector pixel and its contribution to the extinction value detected on that pixel. Using this approach, we construct a near-exact projector and backprojector that can be used especially for algebraic reconstruction techniques. We have implemented this cutting voxel projector and a less accurate, speed-optimized version of it together with two established projectors, a ray tracing projector based on Siddon's algorithm and a TT footprint projector. We show that the cutting voxel projector achieves, especially for large cone beam angles, noticeably higher accuracy than the TT projector. Moreover, our implementation of the relaxed version of the cutting voxel projector is significantly faster than current footprint projector implementations. We further show that Siddon's algorithm with comparable accuracy would be much slower than the cutting voxel projector. All algorithms are implemented within an open source framework for algebraic reconstruction in OpenCL 1.2 and C++ and are optimized for GPU computation. They are published as open-source software under the GNU GPL 3 license, see https://github.com/kulvait/KCT_cbct.

Magnesium (Mg)-based implants have become an attractive alternative to conventional permanent implants in the orthopedic field. While biocompatibility, degradation kinetics, and osseointegration of Mg-based implants have been mostly investigated, the impact of degradation products on bone remodeling and potential systemic effects remains unclear. The aim of this study was to evaluate the early and mid-term local and systemic tissue responses of degrading ultrahigh-purity ZX00 (Mg-Zn-Ca alloy) and ultrahigh-purity Mg (XHP-Mg) pins in a juvenile healthy rat model. The potential differences between implant types (degradable vs. permanent), implantation, and age-related changes were investigated using titanium (Ti), sham-operated, and control groups (non-intervention), respectively. Degradation products of ZX00 and XHP-Mg pins promote osteogenesis in the medullary cavity by upregulating the expression levels of Bmp2 and Opg within 14 days post-surgery. The higher degradation rate of XHP-Mg resulted in the accumulation of degradation products starting from day 3 and upregulation of different genes, particularly Ccl2 and Cepbp. Besides good osseointegration and new bone tissue formation, we found a more parallel hydroxyapatite/collagen orientation along Mg-based pins in the perimeter region compared to Ti pins. In the liver, reduced glycogen levels in Mg-based pins indicated that degradation products promote glycogenolysis, while only the ZX00 group showed a higher serum glucagon level on day 14. Results suggest that degrading ZX00 and XHP-Mg pins stimulate osteogenesis mainly via Bmp2 and Opg and promote glycogenolysis in the liver, while the higher degradation rate of XHP-Mg pins resulted in upregulation of different genes and metabolites. Statement of significance: Bioresorbable magnesium (Mg)-based implants are promising alternative candidates for orthopedic interventions. Until now, a few in vivo studies explored how Mg-based implants promote osteogenesis in the medullary cavity and modulate systemic tissue responses. Herein, results demonstrate i) the degradation rate of the Mg-based implants has a crucial effect on osteogenesis via regulating Bmp2 and Opg expression in the medullary cavity, ii) a parallel HAp/collagen matrix pattern in ZX00 and XHP-Mg groups compared to the Ti group, iii) both Mg pins promote glycogenolysis in the liver. Our findings highlight the dual role of Mg-based

Any pores formed during laser welding of copper hairpins affect the structural integrity and the mechanical/electrical functionality of the joint. We report on investigations using synchrotron X-ray imaging techniques to observe the formation of the pores in the processing zone while welding. It was found that all pores are formed at the joint gap and that the small pores are distributed throughout the complete joint volume as a result of the melt flow induced by the movement of the laser beam. This insight has led to the development of a welding strategy that minimizes pore formation by avoiding the movement of the laser beam across the joint gap. This was achieved by rapid beam shaping based on coherent beam combining (CBC) technology.

Virtual histology is an emerging field in biomedicine that enables three-dimensional tissue visualization using X-ray micro-computed tomography. However, the method still lacks the specificity of conventional histology, in which parts of the tissue are selectively highlighted using targeted stains. Though some first X-ray stains have been developed to address this issue, their precise location and quantity inside the tissue volume remain largely unknown. In this work, we present a novel approach to virtual histology that simultaneously captures electron number density and X-ray attenuation values through modulation-based X-ray imaging with a structured phase modulator. These complementary measurements enable decomposition of tissue volumes into basis materials, which allows the extraction of three-dimensional maps of molar contrast agent distribution alongside morphological details on the micrometer scale – here demonstrated on murine kidneys. The concentration values are validated against the established method of K-edge subtraction imaging. We also create a direct bridge from X-ray to visible light imaging by detecting the same stain both using classical histology and our proposed X-ray approach. Our methodology opens new possibilities for biomedical research into disease progression by providing quantitative three-dimensional stain mapping across entire tissue volumes alongside high-contrast morphology, enabling deeper insights into disease mechanisms.