scholarly journals Bragg coherent imaging of nanoprecipitates: role of superstructure reflections

2020 ◽  
Vol 53 (5) ◽  
pp. 1353-1369
Author(s):  
Maxime Dupraz ◽  
Steven J. Leake ◽  
Marie-Ingrid Richard
Keyword(s):  
Strain Field ◽  
Fourth Generation ◽  
Interatomic Potentials ◽  
High Temperature Mechanical Properties ◽  
Coherent Diffraction Imaging ◽  
Kinematic Approximation ◽  
Wide Range ◽  
Ordered Phases ◽  
Diffraction Imaging ◽  
Diffraction Patterns

Coherent precipitation of ordered phases is responsible for providing exceptional high-temperature mechanical properties in a wide range of compositionally complex alloys. Ordered phases are also essential to enhance the magnetic or catalytic properties of alloyed nanoparticles. The present work aims to demonstrate the relevance of Bragg coherent diffraction imaging (BCDI) for studying bulk and thin-film samples or isolated nanoparticles containing coherent nanoprecipitates/ordered phases. The structures of crystals of a few tens of nanometres in size are modelled with realistic interatomic potentials and are relaxed after introduction of coherent ordered nanoprecipitates. Diffraction patterns from fundamental and superstructure reflections are calculated in the kinematic approximation and used as input to retrieve the strain fields using algorithmic inversion. First, the case of single nanoprecipitates is tackled and it is shown that the strain field distribution from the ordered phase is retrieved very accurately. Then, the influence of the order parameter S on the strain field retrieved from the superstructure reflections is investigated. A very accurate strain distribution can be retrieved for partially ordered phases with large and inhomogeneous strains. Subsequently, the relevance of BCDI is evaluated for the study of systems containing many precipitates, and it is demonstrated that the technique is relevant for such systems. Finally, the experimental feasibility of using BCDI to image ordered phases is discussed in the light of the new possibilities offered by fourth-generation synchrotron sources.

scholarly journals Multi-beam X-ray ptychography for high-throughput coherent diffraction imaging

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yudong Yao ◽  
Yi Jiang ◽  
Jeffrey A. Klug ◽  
Michael Wojcik ◽  
Evan R. Maxey ◽  
...  
Keyword(s):  
Fresnel Zone ◽  
Field Of View ◽  
X Ray ◽  
Single Beam ◽  
Coherent Diffraction Imaging ◽  
Diffraction Imaging ◽  
Extended Field ◽  
Resolution Imaging ◽  
Diffraction Patterns ◽  
Scanning Mechanism

Abstract X-ray ptychography is a rapidly developing coherent diffraction imaging technique that provides nanoscale resolution on extended field-of-view. However, the requirement of coherence and the scanning mechanism limit the throughput of ptychographic imaging. In this paper, we propose X-ray ptychography using multiple illuminations instead of single illumination in conventional ptychography. Multiple locations of the sample are simultaneously imaged by spatially separated X-ray beams, therefore, the obtained field-of-view in one scan can be enlarged by a factor equal to the number of illuminations. We have demonstrated this technique experimentally using two X-ray beams focused by a house-made Fresnel zone plate array. Two areas of the object and corresponding double illuminations were successfully reconstructed from diffraction patterns acquired in one scan, with image quality similar with those obtained by conventional single-beam ptychography in sequence. Multi-beam ptychography approach increases the imaging speed, providing an efficient way for high-resolution imaging of large extended specimens.

scholarly journals A convolutional neural network for defect classification in Bragg coherent X-ray diffraction

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Bruce Lim ◽  
Ewen Bellec ◽  
Maxime Dupraz ◽  
Steven Leake ◽  
Andrea Resta ◽  
...  
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
Diffraction Pattern ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Coherent Diffraction Imaging ◽  
The Neural Network ◽  
Diffraction Imaging ◽  
Diffraction Patterns ◽  
Defect Recognition

AbstractCoherent diffraction imaging enables the imaging of individual defects, such as dislocations or stacking faults, in materials. These defects and their surrounding elastic strain fields have a critical influence on the macroscopic properties and functionality of materials. However, their identification in Bragg coherent diffraction imaging remains a challenge and requires significant data mining. The ability to identify defects from the diffraction pattern alone would be a significant advantage when targeting specific defect types and accelerates experiment design and execution. Here, we exploit a computational tool based on a three-dimensional (3D) parametric atomistic model and a convolutional neural network to predict dislocations in a crystal from its 3D coherent diffraction pattern. Simulated diffraction patterns from several thousands of relaxed atomistic configurations of nanocrystals are used to train the neural network and to predict the presence or absence of dislocations as well as their type (screw or edge). Our study paves the way for defect-recognition in 3D coherent diffraction patterns for material science.

Incorporating particle symmetry into orientation determination in single-particle imaging

2018 ◽  
Vol 74 (5) ◽  
pp. 512-517
Author(s):  
Miklós Tegze ◽  
Gábor Bortel
Keyword(s):  
Three Dimensional ◽  
Symmetric Case ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coherent Diffraction Imaging ◽  
Diffraction Imaging ◽  
Diffraction Patterns ◽  
Particle Imaging ◽  
Single Particle Imaging ◽  
Orientation Determination

In coherent-diffraction-imaging experiments X-ray diffraction patterns of identical particles are recorded. The particles are injected into the X-ray free-electron laser (XFEL) beam in random orientations. If the particle has symmetry, finding the orientation of a pattern can be ambiguous. With some modifications, the correlation-maximization method can find the relative orientations of the diffraction patterns for the case of symmetric particles as well. After convergence, the correlation maps show the symmetry of the particle and can be used to determine the symmetry elements and their orientations. The C factor, slightly modified for the symmetric case, can indicate the consistency of the assembled three-dimensional intensity distribution.

scholarly journals Resolution Enhancement in Coherent Diffraction Imaging Using High Dynamic Range Image

Photonics ◽  
2021 ◽  
Vol 8 (9) ◽  
pp. 370
Author(s):  
Yuanyuan Liu ◽  
Qingwen Liu ◽  
Shuangxiang Zhao ◽  
Wenchen Sun ◽  
Bingxin Xu ◽  
...  
Keyword(s):  
Dynamic Range ◽  
High Dynamic Range ◽  
Image Sensor ◽  
High Dynamic Range Imaging ◽  
Range Imaging ◽  
Imaging Technology ◽  
Coherent Diffraction Imaging ◽  
Diffraction Imaging ◽  
High Dynamic ◽  
Diffraction Patterns

In a coherent diffraction imaging (CDI) system, the information of the sample is retrieved from the diffraction patterns recorded by the image sensor via multiple iterations. The limited dynamic range of the image sensor restricts the resolution of the reconstructed sample information. To alleviate this problem, the high dynamic range imaging technology is adopted to increase the signal-to-noise ratio of the diffraction patterns. A sequence of raw diffraction images with differently exposure time are recorded by the image sensor. Then, they are fused to generate a high quality diffraction pattern based on the response function of the image sensor. With the fused diffraction patterns, the resolution of the coherent diffraction imaging can be effectively improved. The experiments on USAF resolution card is carried out to verify the effectiveness of our proposed method, in which the spatial resolution is improved by 1.8 times using the high dynamic range imaging technology.

scholarly journals Oversampling smoothness: an effective algorithm for phase retrieval of noisy diffraction intensities

2013 ◽  
Vol 46 (2) ◽  
pp. 312-318 ◽  
Author(s):  
Jose A. Rodriguez ◽  
Rui Xu ◽  
Chien-Chun Chen ◽  
Yunfei Zou ◽  
Jianwei Miao
Keyword(s):  
Phase Retrieval ◽  
High Harmonic ◽  
Solution Space ◽  
Real Space ◽  
X Ray ◽  
Coherent Diffraction Imaging ◽  
Wide Range ◽  
Diffraction Imaging ◽  
Correlation Information ◽  
Noise Robust

Coherent diffraction imaging (CDI) is high-resolution lensless microscopy that has been applied to image a wide range of specimens using synchrotron radiation, X-ray free-electron lasers, high harmonic generation, soft X-ray lasers and electrons. Despite recent rapid advances, it remains a challenge to reconstruct fine features in weakly scattering objects such as biological specimens from noisy data. Here an effective iterative algorithm, termed oversampling smoothness (OSS), for phase retrieval of noisy diffraction intensities is presented. OSS exploits the correlation information among the pixels or voxels in the region outside of a support in real space. By properly applying spatial frequency filters to the pixels or voxels outside the support at different stages of the iterative process (i.e.a smoothness constraint), OSS finds a balance between the hybrid input–output (HIO) and error reduction (ER) algorithms to search for a global minimum in solution space, while reducing the oscillations in the reconstruction. Both numerical simulations with Poisson noise and experimental data from a biological cell indicate that OSS consistently outperforms the HIO, ER–HIO and noise robust (NR)–HIO algorithms at all noise levels in terms of accuracy and consistency of the reconstructions. It is expected that OSS will find application in the rapidly growing CDI field, as well as other disciplines where phase retrieval from noisy Fourier magnitudes is needed. TheMATLAB(The MathWorks Inc., Natick, MA, USA) source code of the OSS algorithm is freely available from http://www.physics.ucla.edu/research/imaging.

Removal of spurious data in Bragg coherent diffraction imaging: an algorithm for automated data preprocessing

2021 ◽  
Vol 54 (2) ◽  
Author(s):  
Kenley Pelzer ◽  
Nicholas Schwarz ◽  
Ross Harder
Keyword(s):  
Bragg Peak ◽  
Structural Information ◽  
Perfect Crystal ◽  
Fourth Generation ◽  
Light Sources ◽  
Inversion Symmetry ◽  
Multiple Sources ◽  
Automated Method ◽  
Coherent Diffraction Imaging ◽  
Diffraction Imaging

Bragg coherent diffraction imaging (BCDI) provides a powerful tool for obtaining high-resolution structural information from nanocrystalline materials. Here a BCDI sample consisting of a large number of randomly oriented nanoscale crystals is considered. Ideally, only one crystal is oriented to produce a Bragg peak on the detector. However, diffraction from other crystals often produces additional signals on the detector. Before the measured diffraction patterns can be processed into structural images, scientists routinely need to manually identify and remove the `alien' intensities from sources other than the intended crystal. With the development of modern high-coherence storage rings, such as the upgraded Advanced Photon Source (APS), the already slow process of manual preprocessing will be untenable for the large volumes of data that will be produced. An automated method of identifying and deleting alien intensities is proposed. This method exploits the fact that BCDI of a perfect crystal produces diffraction data with inversion symmetry around the Bragg peak. This approach uses the machine learning clustering method DBSCAN to distinguish between diffraction from multiple sources, and then calculates cluster size and inversion symmetry to assess whether clusters of intensity belong to desired data or alien signals. This approach can dramatically reduce the amount of time spent manually processing data, allowing BCDI data processing capabilities to keep pace with the technological advances of fourth-generation synchrotron light sources.

Quantitative nanotomography of amorphous and polycrystalline samples using coherent X-ray diffraction

2019 ◽  
Vol 52 (3) ◽  
pp. 571-578 ◽  
Author(s):  
Y. Chushkin ◽  
F. Zontone ◽  
O. Cherkas ◽  
A. Gibaud
Keyword(s):  
Mass Density ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coherent Diffraction Imaging ◽  
Diffraction Imaging ◽  
Diffraction Patterns ◽  
Better Than

This article presents a combined approach where quantitative forward-scattering coherent diffraction imaging (CDI) is supported by crystal diffraction using 8.1 keV synchrotron X-ray radiation. The method allows the determination of the morphology, mass density and crystallinity of an isolated microscopic specimen. This approach is tested on three homogeneous samples made of different materials with different degrees of crystallinity. The mass density and morphology are revealed using three-dimensional coherent diffraction imaging with a resolution better than 36 nm. The crystallinity is extracted from the diffraction profiles measured simultaneously with coherent diffraction patterns. The presented approach extends CDI to structural characterization of samples when crystallinity aspects are of interest.

scholarly journals Bragg–Laue X-ray dynamical diffraction on perfect and deformed lateral crystalline structures

2016 ◽  
Vol 49 (4) ◽  
pp. 1190-1202 ◽  
Author(s):  
Vasily I. Punegov ◽  
Sergey I. Kolosov ◽  
Konstantin M. Pavlov
Keyword(s):  
Cross Sections ◽  
X Ray Diffraction ◽  
Dynamical Diffraction ◽  
X Ray ◽  
Crystalline Structures ◽  
Coherent Diffraction Imaging ◽  
Diffraction Imaging ◽  
Diffraction Patterns ◽  
Lateral Structures ◽  
Laue Geometry

The new dynamical diffraction approach to X-ray diffraction on lateral crystalline structures has been developed to investigate the angular and spatial distribution of wavefields in the case of the Bragg–Laue geometry in non-perfect lateral structures. This approach allows one to calculate reciprocal space maps for deformed lateral crystals having rectangular cross sections for both the transmitted and reflected wavefields. Numerical modelling is performed for crystals with different lateral sizes, thicknesses and deformations. The approach can be used in coherent diffraction imaging to simulate Fraunhofer diffraction patterns produced by relatively large deformed crystals.

Coherent diffraction imaging: consistency of the assembled three-dimensional distribution

2016 ◽  
Vol 72 (4) ◽  
pp. 459-464 ◽  
Author(s):  
Miklós Tegze ◽  
Gábor Bortel
Keyword(s):  
Structural Information ◽  
Three Dimensional ◽  
Atomic Scale ◽  
Short Pulses ◽  
X Ray ◽  
Coherent Diffraction Imaging ◽  
Imaging Experiment ◽  
Dimensional Distribution ◽  
Diffraction Imaging ◽  
Diffraction Patterns

The short pulses of X-ray free-electron lasers can produce diffraction patterns with structural information before radiation damage destroys the particle. From the recorded diffraction patterns the structure of particles or molecules can be determined on the nano- or even atomic scale. In a coherent diffraction imaging experiment thousands of diffraction patterns of identical particles are recorded and assembled into a three-dimensional distribution which is subsequently used to solve the structure of the particle. It is essential to know, but not always obvious, that the assembled three-dimensional reciprocal-space intensity distribution is really consistent with the measured diffraction patterns. This paper shows that, with the use of correlation maps and a single parameter calculated from them, the consistency of the three-dimensional distribution can be reliably validated.

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