Quantitative 4D X-ray microtomography under extreme conditions: a case study on magma migration

X-ray computed tomography (XCT) is a well known method for three-dimensional characterization of materials that is established as a powerful tool in high-pressure/high-temperature research. The optimization of synchrotron beamlines and the development of fast high-efficiency detectors now allow the addition of a temporal dimension to tomography studies under extreme conditions. Presented here is the experimental setup developed on the PSICHE beamline at SOLEIL to perform high-speed XCT in the Ultra-fast Tomography Paris–Edinburgh cell (UToPEc). The UToPEc is a compact panoramic (165° angular aperture) press optimized for fast tomography that can access 10 GPa and 1700°C. It is installed on a high-speed rotation stage (up to 360° s−1) and allows the acquisition of a full computed tomography (CT) image with micrometre spatial resolution within a second. This marks a major technical breakthrough for time-lapse XCT and the real-time visualization of evolving dynamic systems. In this paper, a practical step-by-step guide to the use of the technique is provided, from the collection of CT images and their reconstruction to performing quantitative analysis, while accounting for the constraints imposed by high-pressure and high-temperature experimentation. The tomographic series allows the tracking of key topological parameters such as phase fractions from 3D volumetric data, and also the evolution of morphological properties (e.g. volume, flatness, dip) of each selected entity. The potential of this 4D tomography is illustrated by percolation experiments of carbonate melts within solid silicates, relevant for magma transfers in the Earth's mantle.

THE CONSTRUCTIVE METHOD FOR CALCULATING OF FRAUNHOFER'S DIFFRACTION PICTURES AND IMAGES OF 3D-OBJECT REFLECTIVE VOLUMETRIC EDGE

In analytical form, the peculiarities of forming Fraunhofer diffraction patterns and images of faces of a volumetric asymmetric edge of an object with an absolutely reflective internal surface in relation to dimensional inspection were investigated. Formulas were obtained for calculating fields in diffraction-limited systems depending on the magnitude of the bevel of the object c , the phase shift j of the wave reflected from the inner surface of the object, and the angular aperture of the coherent optical system for forming and filtering images. It has been established that for metal 3D-objects (j = p), the value of the field in the image of the back face at a point, corresponding to the position of its border is negligible with the depth of focus of the system much less than the thickness of the object. It is shown that when bevels of an object, much less than the size of the Fresnel zone d ~ ( l - wavelength of light, d - thickness of the object) and more than the depth of focus, the displacement of the intensity profile in the image of the front face is proportional and depends on the angle j. With large bevels, when and, the displacement of the front face boundary is inversely proportional to the value. These displacements can lead to systematic errors in measuring the position of the boundaries of the faces of a 3D-object and should be taken into account in precision dimensional inspection.

Probability distribution function of the aperture mass field with large deviation theory

ABSTRACT In the context of tomographic cosmic shear surveys, a theoretical model for the one-point statistics of the aperture mass (Map) is developed. This formalism is based on the application of the large deviation principle to the projected matter density field and more specifically to the angular aperture masses. The latter holds the advantage of being an observable that can be directly extracted from the observed shear field and to be, by construction, independent from the long wave modes. Furthermore, we show that, with the help of a nulling procedure based on the so-called BNT transform, it is possible to build observables that depend only on a finite range of redshifts making them also independent from the small-scale modes. This procedure makes predictions for the shape of the one-point probability distribution function of such an observable very accurate, comparable to what had been previously obtained for 3D observables. Comparisons with specific simulations reveal however inconsistent results showing that synthetic lensing maps were not accurate enough for such refined observables. It points to the need for more precise dedicated numerical developments whose performances could be benchmarked with such observables. We furthermore review the possible systematics that could affect such a formalism in future weak-lensing surveys like Euclid, notably the impact of shape noise as well as leading corrections coming from lend–lens couplings, geodesic deviation, reduced shear and magnification bias.

Capacity of a Radio Vortex Communication System Using a Partial Angular Aperture Receiving Scheme under the Horizontal Non-Kolmogorov Model

A partial receiving scheme based on limited angular aperture multi-beam receiving and demultiplexing can solve the difficulty caused by the divergence of the vortex beam in the conventional whole beam receiving scheme and realize the long-distance transmission of the vortex wave. The propagation of the radio vortex beam in atmospheric turbulence is of significant importance in theoretical study and practical applications. In this paper, the influence of atmospheric turbulence on the performance of a radio vortex (RV) communication system based on a partial angular aperture receiving (PAAR) scheme under the horizontal non-Kolmogorov channel model is studied. The spiral spectrum of the PAAR scheme and the channel capacity of the RV communication system using the PAAR scheme are derived. Simulation results demonstrate that the selected transmission frequency range has a great influence on the RV communication system based on the PAAR scheme, and the choice of the orbital angular momentum (OAM) mode number L has an influence on the propagation distance. The capacity of RV communication systems based on the PAAR scheme increases with the increase of the transmission frequency in the selected transmission frequency range of 10 GHz–60 GHz. When the number of orbital angular momentum (OAM) modes L is small, we can improve the signal-to-noise ratio (SNR) to obtain a larger capacity of the RV communication system based on the PAAR scheme over a longer propagation distance.

High-Contrast and -Resolution 3-D Ultrasonography with a Clinical Linear Transducer Array Scanned in a Rotate-Translate Geometry

We proposed a novel solution for volumetric ultrasound imaging using single-side access 3-D synthetic aperture scanning of a clinical linear array. This solution is based on an advanced scanning geometry and a software-based ultrasound platform. The rotate-translate scanning scheme increases the elevation angular aperture by pivoting the array (−45° to 45°) around its array axis (axis along the row of its elements) and then scans the imaged object for each pivoted angle by translating the array perpendicularly to the rotation axis. A theoretical basis is presented so that the angular and translational scan sampling periods can be best adjusted for any linear transducer array. We experimentally implemented scanning with a 5-MHz array. In vitro characterization was performed with phantoms designed to test resolution and contrast. Spatial resolution assessed based on the full-width half-maximum of images from isolated microspheres was increased by a factor of 3 along the translational direction from a simple translation scan of the array. Moreover, the resolution was uniform over a cross-sectional area of 4.5 cm2. Angular sampling periods were optimized and tapered to decrease the scan duration while maintaining image contrast (contrast at the center of a 5-mm cyst on the order of −26 dB for 4° angular period and a scan duration of 10 s for a 9-cm3 volume). We demonstrated that superior 3-D ultrasound imaging can be obtained with a clinical array using our scanning strategy. This technique offers a promising and flexible alternative to development of costly matrix arrays toward the development of sensitive volumetric ultrasonography.

Technical and Economic Characteristics of Solar Concentrating Modules With Louvered Heliostats

The calculations confirm the high efficiency of using louvered heliostats. The maximum annual energy production by non-tracking solar concentrating modules is achieved with a vertical orientation of the concentrator, which is very important when placing solar modules on the southern facades of buildings. The annual amounts of insolation at the receiver for concentrators with a louvered heliostat with an angular aperture of 26° and 18°, respectively, are on average 2 and 3.4 times higher than the total insolation on a flat surface and 1,6 and 2,2 times higher than insolation by blind surface receiving concentrating modules with similar angular aperture values. The cost of electricity produced when using non-glare concentrating modules with louvre is reduced by 40–60% compared to concentrating modules without louver, and thermal energy by 50%.

Theoretical Bases of the Use of Solar Concentrating Modules With Louvered Heliostats

A functional relationship was obtained linking the position of the Sun, the step of the mirror lamellae of the heliostat, and their orientation to ensure zero blocking and shading losses in the louvered heliostat. Based on the consideration of a three-dimensional problem, the algorithm for calculating the passage of sunlight through the mirror surface of the lamellae and parabolic cylinder allows calculating the flux of solar radiation on the receiving surface of the solar concentrator. An algorithm for controlling lamellar heliostat mirror lamellas has been developed that significantly increases the efficiency of a solar concentrator—using a louvre heliostat with a constant lamella pitch is equivalent to increasing the angular aperture of the concentrator from 26° to 70° without reducing the concentration ratio.

VOLUMETRIC EFFECTS FOR IMAGE FORMATION OF 3D ASYMMETRIC EDGE

The peculiarities for formation of the image of volumetric asymmetric absolutely absorbing edge (the main fragment of constant thickness thick plates) in a diffraction-limited projection system are investigated in analytical form applied to 3D-objects dimensional inspection. Structures and profiles of image intensities for front and back object sides are studied respectively at small and big apertures of the 3D-object optical system for various ratios of object bevel c , the Fresnel zone size d ~ ( l - the light wavelength, d - object thickness) and an angular aperture of the optical system. It is shown that in case when the bevel с << d , the shift of intensity profile of the 3D-edge image, proportional to Fresnel's zone and bevel size, takes place. Formulas for the image profile of the back side are obtained and investigated in case of strong volumetric effects, when the focus-row depth of the system is much less than the object thickness. The obtained results are in good agreement with results of computer simulations.