26 research outputs found

    X-ray multibeam ptychography at up to 20 keV: nano-lithography enhances X-ray nano-imaging

    Full text link
    Non-destructive nano-imaging of the internal structure of solid matter is only feasible using hard X-rays due to their high penetration. The highest resolution images are achieved at synchrotron radiation sources (SRF), offering superior spectral brightness and enabling methods such as X-ray ptychography delivering single-digit nm resolution. However the resolution or field of view is ultimately constrained by the available coherent flux. To address this, the beam's incoherent fraction can be exploited using multiple parallel beams in an approach known as X-ray multibeam ptychography (MBP). This expands the domain of X-ray ptychography to larger samples or more rapid measurements. Both qualities favor the study of complex composite or functional samples, such as catalysts, energy materials, or electronic devices. The challenges of performing ptychography at high energy and with many parallel beams must be overcome to extract the full advantages for extended samples while minimizing beam attenuation. Here, we report the application of MBP with up to 12 beams and at photon energies of 13 and 20 keV. We demonstrate performance for various samples: a Siemens star test pattern, a porous Ni/\ce{Al2O3} catalyst, a microchip, and gold nano-crystal clusters, exceeding the measurement limits of conventional hard X-ray ptychography without compromising image quality

    Flexible plenoptic X-ray microscopy

    Get PDF
    X-ray computed tomography (CT) is an invaluable technique for generating three-dimensional (3D) images of inert or living specimens. X-ray CT is used in many scientific, industrial, and societal fields. Compared to conventional 2D X-ray imaging, CT requires longer acquisition times because up to several thousand projections are required for reconstructing a single high-resolution 3D volume. Plenoptic imaging—an emerging technology in visible light field photography—highlights the potential of capturing quasi-3D information with a single exposure. Here, we show the first demonstration of a flexible plenoptic microscope operating with hard X-rays; it is used to computationally reconstruct images at different depths along the optical axis. The experimental results are consistent with the expected axial refocusing, precision, and spatial resolution. Thus, this proof-of-concept experiment opens the horizons to quasi-3D X-ray imaging, without sample rotation, with spatial resolution of a few hundred nanometres

    High-energy X-ray Transmission Microscopy based on Compound Refractive Lenses

    No full text
    Summary of thesis: In the results of the work presented in this thesis it has been shown theoretically and demonstrated experimentally that lateral chromatic aberration in hard x-ray transmission microscopy can be significantly reduced by focusing the illumination into the center of the objective lens. Utilizing pink beam microscopy, radiography with spatial resolutions better than 200 nm could be achieved at millisecond frame rates, and tomography with the same resolution could be acquired in less than two seconds. Furthermore, Zernike phase contrast has been implemented for the first time in compound refractive lens based microscopy, and estimations are presented that indicates that the use of this phase contrast technique with non-monochromatic illumination is possible, and is compatible with the lateral chromatic correction scheme. It is also shown that with the illumination focused in the objective, Zernike phase contrast can be achieved using modified CRLs, exemplified by employing a lenslet with a circular hole as a negative phase plate. This is essential for pink beam imaging since the localization of a positive phase plate in the focal spot could become quite challenging, considering the focal spot heat load. Demonstrations of both monochromatic and non-monochromatic imaging with HXTM are presented for various test cases, including in-situ eutectic solidification, colloidal crystals from micron sized polymer spheres, and ultra-fast high resolution tomogram data collections. Taking into account the effects of partial coherent illumination chromatic transmission cross-coefficients have been derived, and expressions for optimal coherence lengths and numerical apertures for any bandwidth and resolution requirement, are obtained. In addition, some convenient relations between numerical aperture and longitudinal chromatic aberration have been derived linking the severity of chromatic aberration of compound refractive lenses to their numerical aperture. Finally, a modelling tool for fast evaluation of image quality was implemented and described

    Analytical transmission cross-coefficients for pink beam X-ray microscopy based on compound refractive lenses

    No full text
    Analytical expressions for the transmission cross-coefficients for x-ray microscopes based on compound refractive lenses are derived based on Gaussian approximations of the source shape and energy spectrum. The effects of partial coherence, defocus, beam convergence, as well as lateral and longitudinal chromatic aberrations are accounted for and discussed. Taking the incoherent limit of the transmission cross-coefficients, a compact analytical expression for the modulation transfer function of the system is obtained, and the resulting point, line and edge spread functions are presented. Finally, analytical expressions for optimal numerical aperture, coherence ratio, and bandwidth are given

    Machine-learning-assisted analysis of highly transient X-ray imaging sequences of weld pools

    No full text
    Fusion-based welding and additive manufacturing are two key pillars of manufacturing. Rapidly evolving melt pools are associated with both of these processing approaches. Understanding and controlling the evolution of the melt pools are critical for optimization of such processes. Flow and interface oscillation during those processes are closely linked to the final fusion zone and microstructure formation. Synchrotron X-ray radiography enables observation in real time of transient melt pools in additive manufacturing and welding processes. However, analysis of the large amount of data generated in such experiments are cumbersome. Thus, we have examined the potential to analyse fast time-resolved X-ray image sequences of melt pools with image-based convolutional neural networks. The results demonstrate successful recognition of changes in the fluctuations of melt-pool interfaces associated with rapid-flow evolution.<br/

    Experimental investigation of Gaussian random phase screen model for x-ray diffusers

    No full text
    The beam diffusing properties of stacked layers of diffuser material were evaluated experimentally and compared to a Gaussian random phase screen model. The model was found to give promising accuracy in combination with a Lorentzian auto-correlation model. The tail behaviour of the angular scattering distribution as a function of number of diffusing layers was particularly well described by the model, and in the case of an amorphous carbon diffuser, the model could describe the whole of the scattering distribution convincingly
    corecore