Reflection Efficiency and Spectra Resolutions Ray-Tracing Simulations for the VOXES HAPG Crystal Based Von Hamos Spectrometer

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.

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

Journal of Applied Crystallography ◽

10.1107/s1600576717012626 ◽

2017 ◽

Vol 50 (5) ◽

pp. 1490-1497 ◽

Cited By ~ 2

Author(s):

Christopher Schlesiger ◽

Lars Anklamm ◽

Wolfgang Malzer ◽

Richard Gnewkow ◽

Birgit Kanngießer

Keyword(s):

Ray Tracing ◽

X Ray Diffraction ◽

Multiple Reflections ◽

New Model ◽

X Ray ◽

Additional Information ◽

Diffraction Model ◽

Reflection Model ◽

Mosaic Crystals ◽

Ray Tracing Simulation

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%.

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X-ray topographic determination of the granular structure in a graphite mosaic crystal: a three-dimensional reconstruction

Journal of Applied Crystallography ◽

10.1107/s0021889800005975 ◽

2000 ◽

Vol 33 (4) ◽

pp. 1023-1030 ◽

Cited By ~ 13

Author(s):

M. Ohler ◽

M. Sanchez del Rio ◽

A. Tuffanelli ◽

M. Gambaccini ◽

A. Taibi ◽

...

Keyword(s):

Structural Parameters ◽

Pyrolytic Graphite ◽

Three Dimensional ◽

X Ray ◽

Dimensional Reconstruction ◽

Mosaic Crystals ◽

Spatial Locations ◽

Crystalline Domains

Section topographs recorded at different spatial locations and at different rocking angles of a highly oriented pyrolytic graphite (HOPG) crystal allow three-dimensional maps of the local angular-dependent scattering power to be obtained. This is performed with a direct reconstruction from the intensity distribution on such topographs. The maps allow the extraction of information on local structural parameters such as size, form and internal mosaic spread of crystalline domains. This data analysis leads to a new method for the characterization of mosaic crystals. Perspectives and limits of applicability of this method are discussed.

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Influence of surface relaxation on the contrast of threading edge dislocations in synchrotron X-ray topographs under the condition of g · b = 0 and g · b × l = 0

Journal of Applied Crystallography ◽

10.1107/s160057672100025x ◽

2021 ◽

Vol 54 (2) ◽

Author(s):

Hongyu Peng ◽

Tuerxun Ailihumaer ◽

Fumihiro Fujie ◽

Zeyu Chen ◽

Balaji Raghothamachar ◽

...

Keyword(s):

Ray Tracing ◽

Depth Profiling ◽

Simulation Method ◽

Surface Relaxation ◽

X Ray ◽

Relaxation Effects ◽

Orientation Contrast ◽

Relaxation Depth ◽

Edge Dislocations ◽

Ray Tracing Simulation

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.

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Recent progress in the performance of HAPG based laboratory EXAFS and XANES spectrometers

Journal of Analytical Atomic Spectrometry ◽

10.1039/d0ja00208a ◽

2020 ◽

Vol 35 (10) ◽

pp. 2298-2304

Author(s):

Christopher Schlesiger ◽

Sebastian Praetz ◽

Richard Gnewkow ◽

Wolfgang Malzer ◽

Birgit Kanngießer

Keyword(s):

Fine Structure ◽

Recent Progress ◽

Pyrolytic Graphite ◽

New Developments ◽

X Ray ◽

Xafs Spectroscopy ◽

Absorption Fine ◽

Mosaic Crystals ◽

X Ray Absorption

New developments in the description and modeling of Highly Annealed Pyrolytic Graphite (HAPG) mosaic crystals have led to the possibility of designing optimized optical solutions for X-ray absorption fine structure (XAFS) spectroscopy.

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Studies of c-Axis Threading Screw Dislocations in Hexagonal SiC

MRS Proceedings ◽

10.1557/proc-1069-d02-03 ◽

2008 ◽

Vol 1069 ◽

Author(s):

Yi Chen ◽

Xianrong Huang ◽

Ning Zhang ◽

Govindhan Dhanaraj ◽

Edward Sanchez ◽

...

Keyword(s):

Ray Tracing ◽

Grazing Incidence ◽

Screw Dislocations ◽

Burgers Vector ◽

X Ray ◽

Back Reflection ◽

Partial Dislocations ◽

Ray Tracing Simulation ◽

Vector Magnitude

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.

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