/pdf/high-resolution-x-ray-computed-tomography-in-geosciences-a-3sj7249knj.pdf

High-resolution X-ray computed tomography in geosciences: A review of the current technology and applications

X-ray computer tomography (CT) is fast becoming an accepted tool within the materials science community for the acquisition of 3D images. Here the authors review the current state of the art as CT transforms from a qualitative diagnostic tool to a quantitative one. Our review considers first the image acquisition process, including the use of iterative reconstruction strategies suited to specific segmentation tasks and emerging methods that provide more insight (e.g. fast and high resolution imaging, crystallite (grain) imaging) than conventional attenuation based tomography. Methods and shortcomings of CT are examined for the quantification of 3D volumetric data to extract key topological parameters such as phase fractions, phase contiguity, and damage levels as well as density variations. As a non-destructive technique, CT is an ideal means of following structural development over time via time lapse sequences of 3D images (sometimes called 3D movies or 4D imaging). This includes information nee...

https://www.tandfonline.com/doi/pdf/10.1179/1743280413Y.0000000023

Quantitative X-ray tomography

Phase-contrast x-ray imaging (PCI) is an innovative method that is sensitive to the refraction of the x-rays in matter. PCI is particularly adapted to visualize weakly absorbing details like those often encountered in biology and medicine. In past years, PCI has become one of the most used imaging methods in laboratory and preclinical studies: its unique characteristics allow high contrast 3D visualization of thick and complex samples even at high spatial resolution. Applications have covered a wide range of pathologies and organs, and are more and more often performed in vivo. Several techniques are now available to exploit and visualize the phase-contrast: propagation- and analyzer-based, crystal and grating interferometry and non-interferometric methods like the coded aperture. In this review, covering the last five years, we will give an overview of the main theoretical and experimental developments and of the important steps performed towards the clinical implementation of PCI.

http://iopscience.iop.org/article/10.1088/0031-9155/58/1/R1/pdf

X-ray phase-contrast imaging: from pre-clinical applications towards clinics

High–energy-density materials that undergo conversion and/or alloying reactions hold promise for next-generation lithium (Li) ion batteries. However, these materials experience substantial volume change during electrochemical operation, which causes mechanical fracture of the material and structural disintegration of the electrode, leading to capacity loss. In this work, we use x-ray tomography during battery operation to visualize and quantify the origins and evolution of electrochemical and mechanical degradation. Tomography provides the time-resolved, three-dimensional chemical composition and morphology within individual particles and throughout the electrode. In the model material tin(II) oxide, we witness distributions in onset and rate of core-shell lithiation, crack initiation and growth along preexisting defects, and irreversible distortion of the electrode, highlighting tomography as a tool to guide the development of durable materials and strain-tolerant electrodes.

https://science.sciencemag.org/content/sci/342/6159/716.full.pdf

Visualization and quantification of electrochemical and mechanical degradation in Li ion batteries.

A fast, powerful and stable filter based on combined wavelet and Fourier analysis for the elimination of horizontal or vertical stripes in images is presented and compared with other types of destriping filters. Strict separation between artifacts and original features allowing both, suppression of the unwanted structures and high degree of preservation of the original image information is endeavoured. The results are validated by visual assessments, as well as by quantitative estimation of the image energy loss. The capabilities and the performance of the filter are tested on a number of case studies related to applications in tomographic imaging. The case studies include (i) suppression of waterfall artifacts in electron microscopy images based on focussed ion beam nanotomography, (ii) removal of different types of ring artifacts in synchrotron based X-ray microtomography and (iii) suppression of horizontal stripe artifacts from phase projections in grating interferometry.

/pdf/stripe-and-ring-artifact-removal-with-combined-wavelet-552aur2eiq.pdf

Stripe and ring artifact removal with combined wavelet--Fourier filtering.

Synchrotron-based X-ray Tomographic Microscopy (SRXTM) is nowadays a powerful technique for non-destructive,
high-resolution investigations of a broad kind of materials. High-brilliance and high-coherence third generation
synchrotron radiation facilities allow micrometer and sub-micrometer, quantitative, three-dimensional
imaging within very short time and extend the traditional absorption imaging technique to edge-enhanced
and phase-sensitive measurements. At the Swiss Light Source TOMCAT, a new beamline for TOmographic Microscopy and Coherent rAdiology experimenTs, has been recently built and started regular user operation in
June 2006. The new beamline get photons from a 2.9 T superbend with a critical energy of 11.1 keV. This makes
energies above 20 keV easily accessible. To guarantee the best beam quality (stability and homogeneity), the
number of optical elements has been kept to a minimum. A Double Crystal Multilayer Monochromator (DCMM)
covers an energy range between 8 and 45 keV with a bandwidth of a few percent down to 10-4. The beamline
can also be operated in white-beam mode, providing the ideal conditions for real-time coherent radiology. This
article presents the beamline design, its optical components and the endstation. It further illustrates two recently
developed phase contrast techniques and finally gives an overview of recent research topics which make intense
use of SRXTM.

/pdf/trends-in-synchrotron-based-tomographic-imaging-the-sls-40jj5dedqh.pdf

Trends in synchrotron-based tomographic imaging: the SLS experience

Owing to recent developments in CMOS technology, it is now possible to exploit tomographic microscopy at third-generation synchrotron facilities with unprecedented speeds. Despite this rapid technical progress, one crucial limitation for the investigation of realistic dynamic systems has remained: a generally short total acquisition time at high frame rates due to the limited internal memory of available detectors. To address and solve this shortcoming, a new detection and readout system, coined GigaFRoST, has been developed based on a commercial CMOS sensor, acquiring and streaming data continuously at 7.7 GB s−1 directly to a dedicated backend server. This architecture allows for dynamic data pre-processing as well as data reduction, an increasingly indispensable step considering the vast amounts of data acquired in typical fast tomographic experiments at synchrotron beamlines (up to several tens of TByte per day of raw data).

/pdf/gigafrost-the-gigabit-fast-readout-system-for-tomography-4igumsulro.pdf

GigaFRoST: the gigabit fast readout system for tomography

Phase-sensitive X-ray imaging methods can provide substantially increased contrast over conventional absorption-based imaging, and therefore new and otherwise inaccessible information. Differential phase-contrast (DPC) imaging, which uses a grating interferometer and a phase-stepping technique, has been integrated into TOMCAT, a beamline dedicated to tomographic microscopy and coherent radiology experiments at the Swiss Light Source. Developments have been made focusing on the fast acquisition and post-processing of data to enable a high-throughput of samples, with obvious advantages, also through increasing the efficiency of the detecting system, of helping to reduce radiation dose imparted to the sample. A novel aquarium design allows a vertical rotation axis below the sample with measurements performed in aqueous environment. Optimization of the data acquisition procedure enables a full phase volume (1024 × 1024 pixels × 1000 projections × 9 phase steps, i.e. 9000 projections in total) to be acquired in 20 min (with a pixel size of 7.4 µm), and the subsequent post-processing has been integrated into the beamline pipeline for sinogram generation. Local DPC tomography allows one to focus with higher magnification on a particular region of interest of a sample without the presence of local tomography reconstruction artifacts. Furthermore, `widefield' imaging is shown for DPC scans for the first time, enabling the field of view of the imaging system to be doubled for samples that are larger than the magnification allows. A case study is illustrated focusing on the visualization of soft tissue features, and particularly the substantia nigra of a rat brain. Darkfield images, based on local X-ray scattering, can also be extracted from a grating-based DPC scan: an example of the advantages of darkfield contrast is shown and the potential of darkfield X-ray tomography is discussed.

/pdf/advanced-phase-contrast-imaging-using-a-grating-53pniy1fjt.pdf

Advanced phase-contrast imaging using a grating interferometer

Synchrotron‐based X‐ray Tomographic Microscopy (SRXTM) is nowadays a powerful technique for non‐destructive, high‐resolution investigations of a broad kind of materials. High‐brilliance and high‐coherence third generation synchrotron radiation facilities allow micrometer and sub‐micrometer, quantitative, three‐dimensional imaging within very short time and extend the traditional absorption imaging technique to edge‐enhanced and phase‐sensitive measurements. At the Swiss Light Source, a new, tomography dedicated beamline called TOMCAT has been built recently. The new beamline get photons from a 2.9 T superbend with a critical energy of 11.1 keV. This makes energies above 20 keV easily accessible. To guarantee the best beam quality (stability and homogeneity), the number of optical elements has been kept to a minimum. A Double Crystal Multilayer Monochromator (DCMM) covers an energy range between 8 and 45 keV with a bandwidth of a few percent down to 10−4. The beamline can also be operated in white‐beam mode, providing the ideal conditions for real‐time coherent radiology.

/pdf/tomcat-a-beamline-for-tomographic-microscopy-and-coherent-1cdvockn91.pdf

TOMCAT: A beamline for TOmographic Microscopy and Coherent rAdiology experimenTs

Understanding the formation of materials at elevated temperatures is critical for determining their final properties. Synchrotron-based X-ray tomographic microscopy is an ideal technique for studying such processes because high spatial and temporal resolutions are easily achieved and the technique is non-destructive, meaning additional analyses can take place after data collection. To exploit the state-of-the-art capabilities at the tomographic microscopy and coherent radiology experiments (TOMCAT) beamline of the Swiss Light Source, a general-use moderate-to-high-temperature furnace has been developed. Powered by two diode lasers, it provides controlled localized heating, from 673 to 1973 K, to examine many materials systems and their dynamics in real time. The system can also be operated in various thermal modalities. For example, near-isothermal conditions at a given sample location can be achieved with a prescribed time-dependent temperature. This mode is typically used to study isothermal phase transformations; for example, the formation of equiaxed grains in metallic systems or to nucleate and grow bubble foams in silicate melts under conditions that simulate volcanic processes. In another mode, the power of the laser can be fixed and the specimen moved at a constant speed in a user-defined thermal gradient. This is similar to Bridgman solidification, where the thermal gradient and cooling rate control the microstructure formation. This paper details the experimental set-up and provides multiple proofs-of-concept that illustrate the versatility of using this laser-based heating system to explore, in situ, many elevated-temperature phenomena in a variety of materials.

/pdf/development-of-a-laser-based-heating-system-for-in-situ-3v9ci8s50z.pdf

G. Mikuljan

Papers

Trends in synchrotron-based tomographic imaging: the SLS experience

GigaFRoST: the gigabit fast readout system for tomography

Advanced phase-contrast imaging using a grating interferometer

TOMCAT: A beamline for TOmographic Microscopy and Coherent rAdiology experimenTs

Development of a laser-based heating system for in situ synchrotron-based X-ray tomographic microscopy