Automatic marker-free estimation methods for the axis of rotation in sub-micron X-ray computed tomography

Misalignment of the rotation axis causes severe artifacts in X-ray computed tomography. Calibration of this parameter is often insufficient for sub-micron resolution measurements and needs to be corrected during the post-processing. This correction can be accelerated by various automatic methods. These vary in mechanisms and performance, making them suitable for different use-cases. This work summarizes existing automatic methods for estimating the rotation axis in X-ray computed tomography, with a focus on sub-micron applications. Some of the methods are implemented and compared in the context of a laboratory sub-micron scanner to demonstrate practical considerations of this task

Directional-Sensitive X-ray/Gamma-ray Imager on Board the VZLUSAT-2 CubeSat for Wide Field-of-View Observation of GRBs in Low Earth Orbit

We present a miniaturized and wide field-of-view X-ray and Gamma-ray imager consisting of a segmented 2D optics-collimator coupled to the high-sensitivity semiconductor pixel detector Timepix equipped with a high-Z sensor (CdTe 2000 μm thick). The compact payload has been deployed in low-Earth orbit (LEO) onboard the 3U Cubesat VZLUSAT-2 which was launched on 13 January 2022. The instrument is designed to verify small spacecraft borne observation in open space of hard X-ray and Gamma-ray sources both of celestial and atmospheric origin. High-resolution spectral-sensitive X-ray and Gamma-ray images are provided with enhanced event discrimination and wide field-of-view up to 60°. Description of the instrument together with response evaluation and tests in ground with well-defined sources are presented. The intended observational plan for in-orbit measurements is outlined along with astrophysical goals and issues

マダガスカル -- アジアとアフリカの接点、インド洋の中継地 (フォトエッセイ)

The Photo-Emission and Atomic Resolution Laboratory (PEARL) is a new soft X-ray beamline and surface science laboratory at the Swiss Light Source. PEARL is dedicated to the structural characterization of local bonding geometry at surfaces and interfaces of novel materials, in particular of molecular adsorbates, nanostructured surfaces, and surfaces of complex materials. The main experimental techniques are soft X-ray photoelectron spectroscopy, photoelectron diffraction, and scanning tunneling microscopy (STM). Photoelectron diffraction in angle-scanned mode measures bonding angles of atoms near the emitter atom, and thus allows the orientation of small molecules on a substrate to be determined. In energy scanned mode it measures the distance between the emitter and neighboring atoms; for example, between adsorbate and substrate. STM provides complementary, real-space information, and is particularly useful for comparing the sample quality with reference measurements. In this article, the key features and measured performance data of the beamline and the experimental station are presented. As scientific examples, the adsorbate-substrate distance in hexagonal boron nitride on Ni(111), surface quantum well states in a metal-organic network of dicyano-anthracene on Cu(111), and circular dichroism in the photoelectron diffraction of Cu(111) are discussed

Hard X-ray stereographic microscopy for single-shot differential phase imaging

The characterisation of fast phenomena, exhibiting velocities of metres per second and more, occurring in opaque samples requires adequate X-ray imaging methods for revealing such structures in their natural state. Fast processes are often stochastic in nature and occur in many key technologies such as additive manufacturing or micro-fluidics, e.g. turbulent cavitations or shock-wave propagation. Due to the complexity of such structures and the speed of the dynamic processes involved, it is necessary to collect 3D structural information for each relevant point in time. Sensitivity to small density differences in a sample can be greatly enhanced, especially for soft matter, by exploiting the phase-contrast modality. In this work, we demonstrate a combination of X-ray stereography and differential phase contrast microscopy with a single-shot (i.e. single exposure) acquisition, paving the way to 3D movies by using sequential "shots" to each collect 3D information. We show that we can successfully recover the 3D phase volume of a phantom object using two simultaneously recorded, stereographic X-ray views. The proposed method is extendable to more than two angular projections and has great potential for applications at megahertz X-ray Free Electron Lasers (XFELs), where velocities of up to kilometres per second can be temporally resolved

Hard X-ray stereographic microscopy for single-shot differential phase imaging

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.ISSN:1094-408