| 1. |
- Bellucci, Valerio, et al.
(författare)
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Hard X-ray stereographic microscopy for single-shot differential phase imaging
- 2023
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Ingår i: Optics Express. - 1094-4087. ; 31:11, s. 18399-18406
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Tidskriftsartikel (refereegranskat)abstract
- The characterisation of fast phenomena at the microscopic scale is required for the understanding of catastrophic responses of materials to loads and shocks, the processing of materials by optical or mechanical means, the processes involved in many key technologies such as additive manufacturing and microfluidics, and the mixing of fuels in combustion. Such processes are usually stochastic in nature and occur within the opaque interior volumes of materials or samples, with complex dynamics that evolve in all three dimensions at speeds exceeding many meters per second. There is therefore a need for the ability to record three-dimensional X-ray movies of irreversible processes with resolutions of micrometers and frame rates of microseconds. Here we demonstrate a method to achieve this by recording a stereo phase-contrast image pair in a single exposure. The two images are combined computationally to reconstruct a 3D model of the object. The method is extendable to more than two simultaneous views. When combined with megahertz pulse trains of X-ray free-electron lasers (XFELs) it will be possible to create movies able to resolve 3D trajectories with velocities of kilometers per second.
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| 2. |
- Birnsteinova, Sarlota, et al.
(författare)
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Online dynamic flat-field correction for MHz microscopy data at European XFEL
- 2023
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Ingår i: Journal of Synchrotron Radiation. - 1600-5775. ; 30:6, s. 1030-1037
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Tidskriftsartikel (refereegranskat)abstract
- The high pulse intensity and repetition rate of the European X-ray Free-Electron Laser (EuXFEL) provide superior temporal resolution compared with other X-ray sources. In combination with MHz X-ray microscopy techniques, it offers a unique opportunity to achieve superior contrast and spatial resolution in applications demanding high temporal resolution. In both live visualization and offline data analysis for microscopy experiments, baseline normalization is essential for further processing steps such as phase retrieval and modal decomposition. In addition, access to normalized projections during data acquisition can play an important role in decision-making and improve the quality of the data. However, the stochastic nature of X-ray free-electron laser sources hinders the use of standard flat-field normalization methods during MHz X-ray microscopy experiments. Here, an online (i.e. near real-time) dynamic flat-field correction method based on principal component analysis of dynamically evolving flat-field images is presented. The method is used for the normalization of individual X-ray projections and has been implemented as a near real-time analysis tool at the Single Particles, Clusters, and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) instrument of EuXFEL.
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| 3. |
- Guo, Rui, et al.
(författare)
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Deep-learning image enhancement and fibre segmentation from time-resolved computed tomography of fibre-reinforced composites
- 2023
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Ingår i: Composites Science and Technology. - 0266-3538. ; 244
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring the microstructure and damage development of fibre-reinforced composites during loading is crucial to understanding their mechanical properties. Time-resolved X-ray computed tomography enables such an in-situ, non-destructive study. However, the photon flux and fibre-matrix contrast limit its achievable spatial and temporal resolution. In this paper, we push the limits of temporal and spatial resolution for the microstructural analysis of unidirectional continuous carbon fibre-reinforced epoxy composites by establishing a new pipeline based on CycleGAN for unsupervised super-resolution and denoising and U-Net-id for individual fibre segmentation. After illustrating the benefits of a 3D CycleGAN over a 2D one, we show that data enhanced by this pipeline can yield similar segmentation quality to that of a slow-acquisition, high-quality scan that took up to 200 times longer to acquire. This pipeline, therefore, enables more robust data extraction from fast time-resolved X-ray tomography, removing a critical stumbling block for this technique.
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| 4. |
- Li, Tang, et al.
(författare)
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Dose-efficient scanning Compton X-ray microscopy
- 2023
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Ingår i: Light: Science and Applications. - 2095-5545. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The highest resolution of images of soft matter and biological materials is ultimately limited by modification of the structure, induced by the necessarily high energy of short-wavelength radiation. Imaging the inelastically scattered X-rays at a photon energy of 60 keV (0.02 nm wavelength) offers greater signal per energy transferred to the sample than coherent-scattering techniques such as phase-contrast microscopy and projection holography. We present images of dried, unstained, and unfixed biological objects obtained by scanning Compton X-ray microscopy, at a resolution of about 70 nm. This microscope was realised using novel wedged multilayer Laue lenses that were fabricated to sub-ångström precision, a new wavefront measurement scheme for hard X rays, and efficient pixel-array detectors. The doses required to form these images were as little as 0.02% of the tolerable dose and 0.05% of that needed for phase-contrast imaging at similar resolution using 17 keV photon energy. The images obtained provide a quantitative map of the projected mass density in the sample, as confirmed by imaging a silicon wedge. Based on these results, we find that it should be possible to obtain radiation damage-free images of biological samples at a resolution below 10 nm.
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| 5. |
- Reuter, Fabian, et al.
(författare)
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Laser-induced, single droplet fragmentation dynamics revealed through megahertz x-ray microscopy
- 2023
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Ingår i: Physics of Fluids. - 1070-6631. ; 35:11
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Tidskriftsartikel (refereegranskat)abstract
- The fragmentation dynamics of single water droplets from laser irradiation is studied with megahertz frame rate x-ray microscopy. Owed to the nearly refraction-free and penetrating imaging technique, we could look into the interior of the droplet and reveal that two mechanisms are responsible for the initial explosive fragmentation of the droplet. First, reflection and diffraction of the laser beam at the droplet interface result in the formation of laser ray caustics that lead to non-homogeneous heating of the droplet, locally above the critical temperature. Second, homogeneous cavitation in the droplet that is likely caused from shockwaves reflected as tension waves at the acoustic soft boundaries of the droplet. Further atomization occurs in three stages, first a fine sub-micrometer sized mist forms on the side of the droplet posterior to laser incidence, then micrometer sized droplets are expelled from the rim of an expanding liquid sheet, and finally into droplets of larger size through hole and ligament formation in the thinning liquid sheet where ligaments pinch off.
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| 6. |
- Soyama, Hitoshi, et al.
(författare)
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Revealing the origins of vortex cavitation in a Venturi tube by high speed X-ray imaging
- 2023
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Ingår i: Ultrasonics Sonochemistry. - 1350-4177. ; 101
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic cavitation is useful in many processing applications, for example, in chemical reactors, water treatment and biochemical engineering. An important type of hydrodynamic cavitation that occurs in a Venturi tube is vortex cavitation known to cause luminescence whose intensity is closely related to the size and number of cavitation events. However, the mechanistic origins of bubbles constituting vortex cavitation remains unclear, although it has been concluded that the pressure fields generated by the cavitation collapse strongly depends on the bubble geometry. The common view is that vortex cavitation consists of numerous small spherical bubbles. In the present paper, aspects of vortex cavitation arising in a Venturi tube were visualized using high-speed X-ray imaging at SPring-8 and European XFEL. It was discovered that vortex cavitation in a Venturi tube consisted of angulated rather than spherical bubbles. The tangential velocity of the surface of vortex cavitation was assessed considering the Rankine vortex model.
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| 7. |
- Villanueva Perez, Pablo, et al.
(författare)
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Megahertz X-ray Multi-projection imaging
- 2023
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Ingår i: arXiv.org. - 2331-8422.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- X-ray time-resolved tomography is one of the most popular X-raytechniques to probe dynamics in three dimensions (3D). Recent developments in time-resolved tomography opened the possibility of recordingkilohertz-rate 3D movies. However, tomography requires rotating thesample with respect to the X-ray beam, which prevents characterization of faster structural dynamics. Here, we present megahertz (MHz)X-ray multi-projection imaging (MHz-XMPI), a technique capable ofrecording volumetric information at MHz rates and micrometer resolution without scanning the sample. We achieved this by harnessing theunique megahertz pulse structure and intensity of the European X-rayFree-electron Laser with a combination of novel detection and reconstruction approaches that do not require sample rotations. Our approachenables generating multiple X-ray probes that simultaneously record several angular projections for each pulse in the megahertz pulse burst.We provide a proof-of-concept demonstration of the MHz-XMPI technique’s capability to probe 4D (3D+time) information on stochasticphenomena and non-reproducible processes three orders of magnitudefaster than state-of-the-art time-resolved X-ray tomography, by generating 3D movies of binary droplet collisions. We anticipate that MHz-XMPIwill enable in-situ and operando studies that were impossible before,either due to the lack of temporal resolution or because the systemswere opaque (such as for MHz imaging based on optical microscopy).
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| 8. |
- Zhang, Yuhe, et al.
(författare)
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ONIX : an X-ray deep-learning tool for 3D reconstructions from sparse views
- 2023
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Ingår i: Applied Research. - 2702-4288. ; 2:4
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved three-dimensional (3D) X-ray imaging techniques rely on obtaining 3D information for each time point and are crucial for materials-science applications in academia and industry. Standard 3D X-ray imaging techniques like tomography and confocal microscopy access 3D information by scanning the sample with respect to the X-ray source. However, the scanning process limits the temporal resolution when studying dynamics and is not feasible for many materials-science applications, such as cell-wall rupture of metallic foams. Alternatives to obtaining 3D information when scanning is not possible are X-ray stereoscopy and multi-projection imaging, but these approaches suffer from limited volumetric information as they only acquire a very small number of views or projections compared to traditional 3D scanning techniques. Here, we present optimized neural implicit X-ray imaging (ONIX), a deep-learning algorithm capable of retrieving a continuous 3D object representation from only a small and limited set of sparse projections. ONIX is based on an accurate differentiable model of the physics of X-ray propagation. It generalizes across different instances of similar samples to overcome the limited volumetric information provided by limited sparse views. We demonstrate the capabilities of ONIX compared to state-of-the-art tomographic reconstruction algorithms by applying it to simulated and experimental datasets, where a maximum of eight projections are acquired. ONIX, although it does not have access to any volumetric information, outperforms unsupervised reconstruction algorithms, which reconstruct using single instances without generalization over different instances. We anticipate that ONIX will become a crucial tool for the X-ray community by (i) enabling the study of fast dynamics not possible today when implemented together with X-ray multi-projection imaging and (ii) enhancing the volumetric information and capabilities of X-ray stereoscopic imaging.
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