A new model for the description of X-ray diffraction from mosaic crystals for ray-tracing calculations

2017 ◽  
Vol 50 (5) ◽  
pp. 1490-1497 ◽  
Author(s):  
Christopher Schlesiger ◽  
Lars Anklamm ◽  
Wolfgang Malzer ◽  
Richard Gnewkow ◽  
Birgit Kanngießer

This paper presents the development of a new reflection model for describing X-ray diffraction from mosaic crystals. In contrast to the well established diffraction model of Zachariasen [Zachariasen (1994),Theory of X-ray Diffraction in Crystals. Mineola: Dover Publications], it gives additional information on the spatial reflection behaviour and not just on the depth-integrated reflectivity of the crystal material. The new reflection model enables a concrete description of mosaic crystal performance in an arbitrary X-ray spectrometer configuration. Multiple reflections inside the crystal are described by splitting the calculation into a discrete number of reflections. Hence, the influence of each number of reflections is investigated, leading to a laterally resolved solution for the reflectivity. In addition, the model can use a mosaicity of arbitrary shape. This is important because the present work uses a Lorentzian-shaped mosaicity instead of a Gaussian one, which is usually the case in the most widely used simulation programs. A comparison between the new model and that of Zachariasen is performed, and it predicts a similar integrated reflectivity with a deviation lower than 0.7%. Further, a ray-tracing simulation with multiple reflections based on the new model is compared with a measurement, showing a deviation of lower than 5%.

2021 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Veronica De Leo ◽  
Alessandro Scordo ◽  
Catalina Curceanu ◽  
Marco Miliucci ◽  
Florin Sirghi

The VOXES collaboration at INFN National Laboratories of Frascati developed a prototype of a high resolution Von Hamos X-ray spectrometer using HAPG (Highly Annealed Pyrolytic Graphite) mosaic crystals. This technology allows the employment of extended isotropic sources and could find application in several physics fields. The capability of the spectrometer to reach energy precision and resolution below 1 and 10 eV, respectively, when used with wide sources, has been already demonstrated. Recently, the response of this device, for a ρ = 206.7 mm cylindrically bent HAPG crystal using CuKα1,2 and FeKα1,2 XRF lines, has been investigated in terms of reflection efficiency by a dedicated ray-tracing simulation. Details of the simulation procedure and the comparison with the experimental results are presented. This study is crucial in order to retrieve information on the spectrometer signal collection efficiency, especially in the energy range in which the standard calibration procedures cannot be applied.


2021 ◽  
Vol 54 (2) ◽  
Author(s):  
Hongyu Peng ◽  
Tuerxun Ailihumaer ◽  
Fumihiro Fujie ◽  
Zeyu Chen ◽  
Balaji Raghothamachar ◽  
...  

Residual contrast of threading edge dislocations is observed in synchrotron back-reflection X-ray topographs of 4H-SiC epitaxial wafers recorded using basal plane reflections where both g · b = 0 and g · b × l = 0. The ray-tracing simulation method based on the orientation contrast formation mechanism is applied to simulate images of such dislocations by applying surface relaxation effects. The simulated contrast features match the observed features on X-ray topographs, clearly demonstrating that the contrast is dominated by surface relaxation. Depth profiling indicates that the surface relaxation primarily takes place within a depth of 5 µm below the surface.


2005 ◽  
Vol 20 (12) ◽  
pp. 3270-3273 ◽  
Author(s):  
F. Berberich ◽  
H. Graafsma ◽  
B. Rousseau ◽  
A. Canizares ◽  
R. Ramy Ratiarison ◽  
...  

A unique combination of in situ synchrotron x-ray diffraction and in situ micro-Raman spectroscopy was used to study the growth process of YBa2Cu3O6+x films obtained by metal organic decomposition using trifluoroacetate precursor on LaAlO3 substrates. The techniques give complementary information: x-ray diffraction gives insight into the structural growth, whereas micro-Raman spectroscopy gives information of the chemical composition with additional information on the texture. To perform both experiments in situ, a special high-temperature process chamber was designed.


1997 ◽  
Vol 07 (03n04) ◽  
pp. 117-133 ◽  
Author(s):  
T. Tadic ◽  
Y. Mokuno ◽  
Y. Horino ◽  
M. Jaksic

Numerical calculations of the effect of the finite dimensions and orientations of source and crystal are presented for plane and von Hamos Bragg crystal spectrometers for PIXE analysis, combined with a position sensitive (X-ray) detector. Analytical studies of all effects are provided. It is shown that some parameters can produce line shifts and asymmetries. A numerical model for an X-ray diffraction ray-tracing procedure for a crystal Bragg spectrometer is described.


1990 ◽  
Vol 5 (5) ◽  
pp. 1083-1091 ◽  
Author(s):  
Manuel Ocaña ◽  
Egon Matijević

Spherical and rod-like SnO2 particles of narrow size distribution have been obtained by aging at 100°C acidified tin(IV) chloride solutions in the presence of urea or formamide. It was shown that spherical particles, the x-ray diffraction of which was characteristic of cassiterite, consisted of a large number of much smaller subunits. The rod-like particles had the same structure, but of higher degree of crystallinity. Infrared spectra of these powders were evaluated in terms of the theory of the average dielectric constant (TADC), in order to gain additional information on the particle morphology and the state of aggregation.


1989 ◽  
Vol 33 ◽  
pp. 1-11 ◽  
Author(s):  
B. K. Tanner

AbstractUse of a reference crystal to condition the beam in the double-axis diffractometer permits the Bragg peak width to be reduced to the correlation of the two crystal reflecting ranges. Some recent applications of double axis diffractometry to the study of heteroepitaxial layers are discussed. The advantages of multiple reflections for beam conditioning and the four reflection DuMond monochromator are examined. Glancing incidence and exit diffractometry permits the study of very thin layers, down to a few tens of nanometres in thickness and both synchrotron radiation and skew reflections can be used to tune the glancing angle close to the critical angle. Recent applications of triple-axis diffraction, where an analyzer crystal is used after the specimen, to the study of very thin single epitaxial layers and multiquantum well structures are reviewed.


2008 ◽  
Vol 1069 ◽  
Author(s):  
Yi Chen ◽  
Xianrong Huang ◽  
Ning Zhang ◽  
Govindhan Dhanaraj ◽  
Edward Sanchez ◽  
...  

ABSTRACTIn our study, closed-core threading screw dislocations and micropipes were studied using synchrotron x-ray topography of various geometries. The Burgers vector magnitude of TSDs can be quantitatively determined from their dimensions in back-reflection x-ray topography, based on ray-tracing simulation and this has been verified by the images of elementary TSDs. Dislocation senses of closed-core threading screw dislocations and micropipes can be revealed by grazing-incidence x-ray topography. The threading screw dislocations can be converted into Frank partial dislocations on the basal planes and this has been confirmed by transmission synchrotron x-ray topography.


1999 ◽  
Vol 13 (09n10) ◽  
pp. 991-996
Author(s):  
M. Salvato ◽  
C. Attanasio ◽  
G. Carbone ◽  
T. Di Luccio ◽  
S. L. Prischepa ◽  
...  

High temperature superconducting multilayers have been obtained depositing Bi2Sr2CuO6+δ(2201) and ACuO2 layers, where A is Ca or Sr, by Molecular Beam Epitaxy (MBE) on MgO and SrTiO3 substrates. The samples, formed by a sequence of 2201/ACuO2 bilayers, have different thickness of ACuO2 layers while the thickness of the 2201 layers is kept constant. The surface structure of each layer has been monitored by in situ Reflection High Energy Electron Diffraction (RHEED) analysis which has confirmed a 2D nucleation growth. X-ray diffraction (XRD) analysis has been used to confirm that the layered structure has been obtained. Moreover, one-dimensional X-ray kinematic diffraction model has been developed to interpret the experimental data and to estimate the period of the multilayers. Resistive measurements have shown that the electrical properties of the samples strongly depend on the thickness of the ACuO2 layers.


2014 ◽  
Vol 53 (4) ◽  
pp. 047104 ◽  
Author(s):  
Claudio Ferrari ◽  
Elisa Buffagni ◽  
Elisa Bonnini ◽  
Andrea Zappettini

2003 ◽  
Vol 36 (1) ◽  
pp. 146-153 ◽  
Author(s):  
A. Plançon

The stacking parameters and nature of a mixed-layer mineral (m.l.m.) are generally determined by modelling its X-ray diffraction pattern. For m.l.m.'s containing electrically charged layers it has been assumed, until now, that they can be described by stacking of electrically neutral units that associate the charged layer itself and a compensating interlayer charge. Some consequences of this hypothesis are difficult to justify,e.g.quite different charges to compensate the same types of interlayers, or, on the contrary, the same charge to compensate quite different types of interlayers. A new model is proposed, allowing a description of any lamellar structure containing electrically charged layers. The mathematical formalism for the diffracted intensities of such a model is developed.


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