scholarly journals Lensless Reflection Imaging of Obliquely Illuminated Objects I: Choosing a Domain for Phase Retrieval and Ptychography

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1439
Author(s):  
Igor A. Artyukov ◽  
Nikolay L. Popov ◽  
Alexander V. Vinogradov
Keyword(s):  
Inverse Problem ◽  
Phase Retrieval ◽  
Extreme Ultraviolet ◽  
X Rays ◽  
Reflection Mode ◽  
Optical Elements ◽  
Diffraction Integral ◽  
Diffraction Patterns ◽  
Set Up ◽  
Object Material

Ptychography is a lensless imaging technology that is validated from hard X-rays to terahertz spectral range. It is most attractive for extreme ultraviolet (EUV) and X-rays as optical elements are expensive and often not available. Typically, the set up involves coherently illuminated object that directs the scattered radiation normally to detector which is parallel to the object plane. Computer processing of diffraction patterns obtained when scanning the object gives the image, more precisely, the distribution of intensity and phase on its surface. However, this scheme is inefficient for EUV and X-rays due to poor reflectivity and low penetration in all materials. Reflection mode ptychography solves the problem if illumination angles do not exceed the critical angle of object material. Changing the geometry of experiment changes physical and mathematical model of image formation. Including: diffraction integral describing beam propagation from object to detector, inverse problem, optimization of object illumination angle, position and orientation of detector, choosing size and grid of coordinate and frequency computer domains. This paper considers the wavefield scattered to detector by obliquely illuminated object and determines a domain for processing of obtained scans. Solution of inverse problem with phase retrieval and resulting numerical images will be presented in the next paper.

scholarly journals A High Resolution XUV Grating Monochromator for the Spectral Selection of Ultrashort Harmonic Pulses

2019 ◽  
Vol 9 (12) ◽  
pp. 2502
Author(s):  
Nicola Fabris ◽  
Paolo Miotti ◽  
Fabio Frassetto ◽  
Luca Poletto
Keyword(s):  
Extreme Ultraviolet ◽  
Spectral Lines ◽  
Resolving Power ◽  
High Spectral Resolution ◽  
Test Case ◽  
Optical Elements ◽  
Broad Energy Range ◽  
Grating Monochromator ◽  
Set Up ◽  
Selection Of

A new monochromator with high spectral resolution in the extreme ultraviolet (XUV) has been developed for high-order laser harmonics selection. The system has three optical elements—a cylindrical (or spherical) focusing mirror, a uniform-line-spaced plane grating, and a plane mirror. The last element is required to maintain the focus on a fixed vertical slit when the grating subtended angle is changed in order to minimize the spectral defocusing aberration. The parameters of the focusing mirror are determined to introduce a coma that compensates for the coma given by the grating. The possibility of using two interchangeable gratings made the set-up optimized for a broad energy range of 12–50 eV. As a design test case, the set-up has been applied to a selection of the discrete spectral lines emitted by a gas-discharge lamp as the XUV source, obtaining a resolving power E/ Δ E > 3000.

scholarly journals Direct phasing in femtosecond nanocrystallography. I. Diffraction characteristics

2014 ◽  
Vol 70 (2) ◽  
pp. 143-153 ◽  
Author(s):  
Joe P. J. Chen ◽  
John C. H. Spence ◽  
Rick P. Millane
Keyword(s):  
Phase Retrieval ◽  
Molecular Structures ◽  
X Rays ◽  
Noise Levels ◽  
Fourier Amplitude ◽  
Acta Cryst ◽  
Short Pulses ◽  
Noise Characteristics ◽  
Small Crystals ◽  
Diffraction Patterns

X-ray free-electron lasers solve a number of difficulties in protein crystallography by providing intense but ultra-short pulses of X-rays, allowing collection of useful diffraction data from nanocrystals. Whereas the diffraction from large crystals corresponds only to samples of the Fourier amplitude of the molecular transform at the Bragg peaks, diffraction from very small crystals allows measurement of the diffraction amplitudes between the Bragg samples. Although highly attenuated, these additional samples offer the possibility of iterative phase retrieval without the use of ancillary experimental data [Spenceet al.(2011).Opt. Express,19, 2866–2873]. This first of a series of two papers examines in detail the characteristics of diffraction patterns from collections of nanocrystals, estimation of the molecular transform and the noise characteristics of the measurements. The second paper [Chenet al.(2014).Acta Cryst.A70, 154–161] examines iterative phase-retrieval methods for reconstructing molecular structures in the presence of the variable noise levels in such data.

Shape transform phasing of edgy nanocrystals

2019 ◽  
Vol 75 (2) ◽  
pp. 239-259 ◽  
Author(s):  
J. P. J. Chen ◽  
J. J. Donatelli ◽  
K. E. Schmidt ◽  
R. A. Kirian
Keyword(s):  
Phase Retrieval ◽  
Crystal Surface ◽  
Simulated Data ◽  
Partial Coherence ◽  
Retrieval Algorithm ◽  
X Rays ◽  
Additional Information ◽  
Interference Signals ◽  
Diffraction Patterns ◽  
Phase Retrieval Algorithm

Diffraction patterns from small protein crystals illuminated by highly coherent X-rays often contain measurable interference signals between Bragg peaks. This coherent `shape transform' signal introduces enough additional information to allow the molecular densities to be determined from the diffracted intensities directly, without prior information or resolution restrictions. However, the various correlations amongst molecular occupancies/vacancies at the crystal surface result in a subtle yet critical problem in shape transform phasing whereby the sublattices of symmetry-related molecules exhibit a form of partial coherence amongst lattice sites when an average is taken over many crystal patterns. Here an iterative phase retrieval algorithm is developed which is capable of treating this problem; it is demonstrated on simulated data.

scholarly journals Dynamic nanoimaging of extended objects via hard X-ray multiple-shot coherent diffraction with projection illumination optics

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yuki Takayama ◽  
Keizo Fukuda ◽  
Motoki Kawashima ◽  
Yuki Aoi ◽  
Daiki Shigematsu ◽  
...  
Keyword(s):  
Phase Retrieval ◽  
Frame Rate ◽  
Retrieval Algorithm ◽  
X Rays ◽  
Full Field ◽  
X Ray ◽  
Cell Functions ◽  
Multiple Shot ◽  
Spatio Temporal ◽  
Diffraction Patterns

AbstractThe quest for understanding the structural mechanisms of material properties and biological cell functions has led to the active development of coherent diffraction imaging (CDI) and its variants in the hard X-ray regime. Herein, we propose multiple-shot CDI, a full-field CDI technique dedicated to the visualisation of local nanostructural dynamics in extended objects at a spatio-temporal resolution beyond that of current instrumentation limitations. Multiple-shot CDI reconstructs a “movie” of local dynamics from time-evolving diffraction patterns, which is compatible with a robust scanning variant, ptychography. We developed projection illumination optics to produce a probe with a well-defined illumination area and a phase retrieval algorithm, establishing a spatio-temporal smoothness constraint for the reliable reconstruction of dynamic images. The numerical simulations and proof-of-concept experiment using synchrotron hard X-rays demonstrated the capability of visualising a dynamic nanostructured object at a frame rate of 10 Hz or higher.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Characterization of Rh/Si multilayer structure by HREM and HAADF

1992 ◽  
Vol 50 (1) ◽  
pp. 122-123
Author(s):  
Y. Cheng ◽  
J. Liu ◽  
M.B. Stearns ◽  
D.G. Steams
Keyword(s):  
Normal Incidence ◽  
High Resolution Electron Microscopy ◽  
X Rays ◽  
Beam Direction ◽  
Cross Sectional ◽  
Optical Elements ◽  
Resolution Electron ◽  
Point To Point ◽  
Better Than

The Rh/Si multilayer (ML) thin films are promising optical elements for soft x-rays since they have a calculated normal incidence reflectivity of ∼60% at a x-ray wavelength of ∼13 nm. However, a reflectivity of only 28% has been attained to date for ML fabricated by dc magnetron sputtering. In order to determine the cause of this degraded reflectivity the microstructure of this ML was examined on cross-sectional specimens with two high-resolution electron microscopy (HREM and HAADF) techniques.Cross-sectional specimens were made from an as-prepared ML sample and from the same ML annealed at 298 °C for 1 and 100 hours. The specimens were imaged using a JEM-4000EX TEM operating at 400 kV with a point-to-point resolution of better than 0.17 nm. The specimens were viewed along Si [110] projection of the substrate, with the (001) Si surface plane parallel to the beam direction.

Structural studies of small amorphous volumes by electron diffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 122-123
Author(s):  
Pierre Moine
Keyword(s):  
Electron Diffraction ◽  
Born Approximation ◽  
Structural Information ◽  
Fundamental Relation ◽  
X Rays ◽  
Structural Studies ◽  
Diffraction Experiment ◽  
Transmission Electron ◽  
Amorphous Structures ◽  
Diffraction Patterns

Qualitatively, amorphous structures can be easily revealed and differentiated from crystalline phases by their Transmission Electron Microscopy (TEM) images and their diffraction patterns (fig.1 and 2) but, for quantitative structural information, electron diffraction pattern intensity analyses are necessary. The parameters describing the structure of an amorphous specimen have been introduced in the context of scattering experiments which have been, so far, the most used techniques to obtain structural information in the form of statistical averages. When only small amorphous volumes (< 1/μm in size or thickness) are available, the much higher scattering of electrons (compared to neutrons or x rays) makes, despite its drawbacks, electron diffraction extremely valuable and often the only feasible technique.In a diffraction experiment, the intensity IN (Q) of a radiation, elastically scattered by N atoms of a sample, is measured and related to the atomic structure, using the fundamental relation (Born approximation) : IN(Q) = |FT[U(r)]|.

scholarly journals More than XRF Mapping: STEAM (Statistically Tailored Elemental Angle Mapper) a Pioneering Analysis Protocol for Pigment Studies

2021 ◽  
Vol 11 (4) ◽  
pp. 1446
Author(s):  
Jacopo Orsilli ◽  
Anna Galli ◽  
Letizia Bonizzoni ◽  
Michele Caccia
Keyword(s):  
Cultural Heritage ◽  
Element Distribution ◽  
Elemental Distribution ◽  
X Rays ◽  
Spectral Angle Mapper ◽  
X Ray ◽  
Fluorescence Radiation ◽  
Set Up ◽  
Non Destructive ◽  
Analysis Protocol

Among the possible variants of X-Ray Fluorescence (XRF), applications exploiting scanning Macro-XRF (MA-XRF) are lately widespread as they allow the visualization of the element distribution maintaining a non-destructive approach. The surface is scanned with a focused or collimated X-ray beam of millimeters or less: analyzing the emitted fluorescence radiation, also elements present below the surface contribute to the elemental distribution image obtained, due to the penetrative nature of X-rays. The importance of this method in the investigation of historical paintings is so obvious—as the elemental distribution obtained can reveal hidden sub-surface layers, including changes made by the artist, or restorations, without any damage to the object—that recently specific international conferences have been held. The present paper summarizes the advantages and limitations of using MA-XRF considering it as an imaging technique, in synergy with other hyperspectral methods, or combining it with spot investigations. The most recent applications in the cultural Heritage field are taken into account, demonstrating how obtained 2D-XRF maps can be of great help in the diagnostic applied on Cultural Heritage materials. Moreover, a pioneering analysis protocol based on the Spectral Angle Mapper (SAM) algorithm is presented, unifying the MA-XRF standard approach with punctual XRF, exploiting information from the mapped area as a database to extend the comprehension to data outside the scanned region, and working independently from the acquisition set-up. Experimental application on some reference pigment layers and a painting by Giotto are presented as validation of the proposed method.

Morphological and synchrotron X-ray microdiffraction studies of large columnar CVD diamond crystallites

1999 ◽  
Vol 32 (5) ◽  
pp. 924-933 ◽  
Author(s):  
A. R. Lang ◽  
A. P. W. Makepeace ◽  
J. E. Butler
Keyword(s):  
Vapour Deposition ◽  
Chemical Vapour ◽  
Coarse Grained ◽  
X Rays ◽  
Small Cross Section ◽  
X Ray ◽  
Chemical Vapour Deposition Diamond ◽  
Core Column ◽  
Diffraction Patterns ◽  
Goniometric Measurements

Optical microscopic and goniometric measurements were combined with microradiography, diffraction-pattern analysis and topography to study a 2 mm thick [001]-texture CVD (chemical vapour deposition) diamond film that had developed a coarse-grained structure composed of separate columnar crystallites. Individual columns were capped by large (001) facets, with widths up to 0.5 mm, and which were smooth but not flat, whereas the column sides were morphologically irregular. The refractive deviation of X-rays transmitted through the crystallites was exploited for delineating facet edges, thereby facilitating the controlled positioning of small-cross-section X-ray beams used for recording diffraction patterns from selected volumes in two representative crystallites. Their structure consisted of a [001]-axial core column surrounded by columns in twin orientation with respect to the core. The diamond volume directly below the (001) facets was free from low-angle boundaries, and no dislocation outcrops on the facets were detected. Significant elastic deformation of this volume was only present close to the facet periphery, where misorientations reached a few milliradians. Lattice imperfection was high in the twins, with ∼1° misorientations.

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