Method of calculating the coherent scattering power of crystals with unknown atomic arrangements and its application in the quantitative phase analysis

Quantitative phase analysis is one of the major applications of X-ray powder diffraction. The essential principle of quantitative phase analysis is that the diffraction intensity of a component phase in a mixture is proportional to its abundance. Nevertheless, the diffraction intensities of the component phases cannot be compared with each other directly since the coherent scattering power per unit cell (or chemical formula) of each component phase is usually different. The coherent scattering power per unit cell of a crystal is well represented by the sum of the squared structure factors, which cannot be calculated directly when the crystal structure data is unavailable. Presented here is a way to approximate the coherent scattering power per unit cell based solely on the unit cell parameters and the chemical contents. This approximation is useful when the atomic coordinates for one or more of the phases in a sample are unavailable. An assessment of the accuracy of the approximation is presented. This assessment indicates that the approximation will likely be within 10% when X-ray powder diffraction data is collected over a sufficient portion of the measurable pattern.

Soft X-ray Lensless Imaging in Reflection Mode

We report on the development and implementation of methodologies dedicated to soft X-ray imaging by coherent scattering in reflection mode. Two complementary approaches are tested, based on Fourier transform holography and on ptychography. A new method for designing holographic masks has been developed. Our results represent a feasibility test and highlight the potential and limitations of imaging in reflection mode. Reflectivity is less efficient than transmission at soft X-ray wavelengths, hampering the acquisition of good quality images. Nonetheless, it has the potential to image a wider set of samples, notably those that are not transparent to soft X-rays. Although the images obtained so far are of modest quality, these results are extremely encouraging for continuing the development of coherent soft X-ray imaging in reflection mode.

Updated detection prospects for relic neutrinos using coherent scattering

We review the existing proposals to detect relic neutrinos using the coherent scattering of a neutrino wind on a test mass. By considering the transformation of the neutrino momentum between reference frames, we demonstrate that the induced acceleration scales with the square of the neutrino mass for unclustered neutrinos, contrary to the existing literature. In addition, we show that there is a large contribution to this effect from coherent neutrino-electron scattering, which can exceed the neutrino-nucleus component by nearly an order of magnitude. Unfortunately, we find that even with this enhancement there are no existing experiments or proposals capable of detecting relic neutrinos using this method.

Morphological and magnetic features of columnar nanostructures CuO

Columnar nanostructures (CNS) were grown by plasma chemical synthesis at a gas mixture pressure of 90% He + 10% O2 200 Pa and substrate temperatures of 340K (sample 1) and 370K (sample 2). The effect of substrate temperature on the morphological, crystalline, magnetic, and impedance properties of CNS was studied. Scanning microscopy (SEM) showed that the morphology of CNS varies significantly from dendritic to wire structure. Energy dispersive X-ray spectroscopy (EDS) showed a change in the stoichiometry of the deficiency samples (Cu52O48) to an excess of oxygen (Cu42O58). X-ray diffraction analysis (XRD) and Rietveld fitting showed that samples 1 and 2 have a monoclinic crystal structure with a large proportion of the amorphous phase, the size of coherent scattering regions (CSR) was 26 nm (sample 1). Magnetic measurements showed that sample 1 exhibits ferromagnetic behavior, and at 6 K a magnetic hysteresis loop appears. Sample 2 from 250 K to room temperature exhibits diamagnetic behavior. A connection was found between the appearance of diamagnetism and a jump in the dielectric constant of sample 2. An assumption was made about the electron-ionic nature of the diamagnetism of sample 2.

Production of nanopowder of cerium (III) fluoride obtained by pulsed electron beam evaporation in vacuum

The method of pulsed electron beam evaporation in vacuum was first used to obtain CeF3 nanopowder (NP). During NP production, a high evaporation rate of the target (~ 7 g/h) and a higher percentage of NP collection (> 72%) were observed, both for fluoride and the previously obtained CeO2 oxide. It was found that the produced NP contains two crystalline phases: hexagonal CeF3 (95 wt.%, coherent scattering region ≈ 8 nm and [Ce-O-F] or [Ce-F]. The magnetic susceptibility of CeF3 nanoparticles (NPles) coincides with the susceptibility of micron particles, indicating the potential for using such NPles as a contrast agent for tomography. High specific surface area (CeO2-270 m2/g, CeF3 – 62 m2/g), large pore volume (0.35-0.11 cm3/g) allow the use of NPles as nanocontainers for drug delivery.

Characterization of size and morphological composition of ablated nanoparticles of cerium dioxide after ultrasonic dispersion and centrifugation in aqueous solution

The paper investigates the size and morphological composition of ablated cerium dioxide nanoparticles after ultrasonic dispersion at centrifugation speeds from 800 to 13400 rpm. A nanodispersed solution of cerium dioxide was deposited onto silicon substrates by the drop method. To characterize the size and morphological composition of cerium dioxide nanoparticles, methods of scanning electron and atomic microscopy were used, and X-ray phase analysis was performed. It was found that ablated cerium dioxide particles in an aqueous solution agglomerated and without centrifugation their average size was 162 nm, after centrifugation their average size varied from 86 nm to 142.5 nm. X-ray phase analysis showed that with an increase in the centrifuge speed, the size of the coherent scattering region decreases, which affects the effectiveness of antioxidant properties, for example, in the Fenton reaction.

A Contrast Calibration Protocol for X-ray Speckle Visibility Spectroscopy

X-ray free electron lasers, with their ultrashort highly coherent pulses, opened up the opportunity of probing ultrafast nano- and atomic-scale dynamics in amorphous and disordered material systems via speckle visibility spectroscopy. However, the anticipated count rate in a typical experiment is usually low. Therefore, visibility needs to be extracted via photon statistics analysis, i.e., by estimating the probabilities of multiple photons per pixel events using pixelated detectors. Considering the realistic X-ray detector responses including charge cloud sharing between pixels, pixel readout noise, and gain non-uniformity, speckle visibility extraction relying on photon assignment algorithms are often computationally demanding and suffer from systematic errors. In this paper, we present a systematic study of the commonly-used algorithms by applying them to an experimental data set containing small-angle coherent scattering with visibility levels ranging from below 1% to ∼60%. We also propose a contrast calibration protocol and show that a computationally lightweight algorithm can be implemented for high-speed correlation evaluation.

Ptychography Reduces Spectral Distortions Intrinsic to Conventional Zone-Plate-Based X-Ray Spectromicroscopy

Scanning transmission X-ray microscopy is a powerful method for mapping chemical phases in nano-materials. The point spread function (PSF) of a conventional zone-plate-based microscope limits the achievable spatial resolution and also results in spatially resolved spectra that do not accurately reflect the spatial heterogeneity of the samples when the scale of the detail approaches the probe size. X-ray ptychography, a coherent-scattering-based imaging scheme that effectively removes the probe from the image data, returns accurate spectra from regions smaller than the probe size. We show through simulation how the long tails on the PSF of an x-ray optic can cause spectral distortion near a boundary between two spectrally distinct regions. The resulting apparent point spectra can appear mixed, with the species on one side of the boundary seeming to be present on the other even at a distance from the boundary equal to several times the spatial resolution. We further demonstrate the effect experimentally and show that ptychographic microscopy can return the expected spectra from a model system, whereas conventional microscopy does not.

Possibility of applying X-ray methods to control the surface quality of a shaft line after finishing

The purpose of the paper is to analyze the application limits of X-ray methods of non-destructive testing of loaded parts; to compare the results of microstresses and deformations of the details’ surface layer by methods and by the method of X-ray diffraction analysis for various modes of processing the detail surface layer. The studies are carried out on a “Dron” diffractometer. The technique and algorithm of X-ray structural studies, namely, “sin2v|/”-method are represented. Residual macro σφ and micro stresses, as well as the sizes of the areas of coherent scattering (D) on the samples surfaces processed in various modes, and their distribution in the near-surface layer are designated. Phase analysis is conducted and the presence of residual austenite. The research object is the operating surface of the 46-19-186 gear tooth after various treatments: after HFC hardening; after HFC hardening, grinding and blasting in depressions; after HFC hardening and fine-finish cutting. The X-ray structural analysis (XRD) technique is presented to determine the residual macro-σφ and microstresses, the sizes of the coherent scattering regions (D) on the surfaces of the samples processed in different modes. The outcomes of X-ray structural analysis are compared with the outcomes of metallographic studiesmaking. It was determined that the stress relaxation during the manufacture of the sample is no more than 10%, and the total instrumental error of the X-ray spectral analysis method is about 1%.