X-ray focusing properties of doubly bent crystals

2017 ◽  
Vol 50 (4) ◽  
pp. 1104-1116 ◽  
Author(s):  
Golamreza Askari Germi ◽  
Sayyed Jalal Pestehe ◽  
Alireza Rastkar Ebrahimzadeh
Keyword(s):  
General Relation ◽  
General Point ◽  
Detector Plane ◽  
Linear Source ◽  
X Ray ◽  
Bent Crystal ◽  
Exact Determination ◽  
Bent Crystals ◽  
Focusing Properties

The focusing properties of several bent crystal geometries, including the newly introduced Pestehe & Askari general point-focusing system [Pestehe & Askari Germi (2012),Opt. Soc. Am. A,29, 68–77; Pestehe & Askari Germi (2012),J. Appl. Cryst.45, 890–901], on an arbitrarily positioned detector plane are investigated and illustrated. The properties of the focal points and the generated images are theoretically related to the local, ℓ, and directional, γ, positions of the detector plane for a given position of a point source on the Rowland circle. A general relation is derived for the detector positioning to obtain a specially focused image. This formula for the polar position of the detector plane, given by the two ℓ and γ variables, enables the exact determination of the system astigmatism and the exact calculation of the sagittal and meridional image positions for the spectrometer under study. The astigmatisms of the above-mentioned bent crystal geometries have been studied, and their sagittal and meridional focal positions and characteristics have been obtained and are illustrated. It is also shown that there is a possibility of designing a spectrometer to focus rays from a linear source onto a point on the Rowland circle.

scholarly journals Improving the energy resolution of bent crystal X-ray spectrometers with position-sensitive detectors

2014 ◽  
Vol 21 (4) ◽  
pp. 762-767 ◽  
Author(s):  
Ari-Pekka Honkanen ◽  
Roberto Verbeni ◽  
Laura Simonelli ◽  
Marco Moretti Sala ◽  
Ali Al-Zein ◽  
...  
Keyword(s):  
High Resolution ◽  
Internal Stress ◽  
Photon Energy ◽  
Energy Resolution ◽  
Preceding Paper ◽  
X Ray ◽  
Bent Crystal ◽  
Position Sensitive ◽  
Position Sensitive Detectors ◽  
Bent Crystals

Wavelength-dispersive high-resolution X-ray spectrometers often employ elastically bent crystals for the wavelength analysis. In a preceding paper [Honkanenet al.(2014).J. Synchrotron Rad.21, 104–110] a theory for quantifying the internal stress of a macroscopically large spherically curved analyser crystal was presented. Here the theory is applied to compensate for the corresponding decrease of the energy resolution. The technique is demonstrated with a Johann-type spectrometer using a spherically bent Si(660) analyser in near-backscattering geometry, where an improvement in the energy resolution from 1.0 eV down to 0.5 eV at 9.7 keV incident photon energy was observed.

scholarly journals X-ray microscopy of laser-produced plasmas with the use of bent crystals

1991 ◽  
Vol 9 (1) ◽  
pp. 135-148 ◽  
Author(s):  
E. Förster ◽  
K. Gäbel ◽  
I. Uschmann
Keyword(s):  
Dynamical Theory ◽  
High Luminosity ◽  
Spectral Window ◽  
X Ray ◽  
Lyman Alpha ◽  
Laser Facility ◽  
Spectral Ranges ◽  
Bent Crystals ◽  
Intercombination Line

X-ray spectroscopical and microscopical methods are used for the determination of the spectral and spatial distribution of X-ray intensity of laser-produced plasmas. The use of Bragg reflections of two-dimensionally bent crystals enables the X-ray microscopical imaging in narrow spectral ranges (Δλ/λ = 10−4 to 10−2) with wavelengths 0.1 nm < λ > 2.6 nm. It is possible to adapt, in the X-ray microscope, the distances, magnification, position, and width of the spectral window to the special conditions of the laser facility. Manufacturing and testing of the two-dimensionally bent crystals requires a great deal of effort. It was demonstrated that a spatial resolution of about 5 μm was achieved, and that the experimentally determined reflectivity was found to be in close agreement with the dynamical theory of X-ray interferences. Due to high luminosity of the X-ray microscope, in experiments with laser-produced plasmas it was necessary to attenuate the radiation with aperture-limiting diaphragms or filters down to 0.01–1% of the original intensity in the case of a magnification of about one. Emission of the resonance line W 1–2, the intercombination line of helium-like ions, and Lyman alpha line were imaged simultaneously with a three-channel microscope. Such images form the foundation for establishing the Ne(r), Tz(r) maps.

Determination of Total Length in Human Permanent Teeth - An Anthropometric Study

2016 ◽  
Vol 695 ◽  
pp. 20-24
Author(s):  
Mugur George Popescu ◽  
Diana Marian ◽  
Ramona Amina Popovici ◽  
Teodora Ștefănescu
Keyword(s):  
Root Canal ◽  
Population Group ◽  
Geographic Area ◽  
Permanent Teeth ◽  
X Ray ◽  
Working Length ◽  
Exact Determination ◽  
Anthropometric Study ◽  
Tooth Length

The correct endodontic treatment involves the exact determination of the working length. This is accomplished by combining several techniques: the tactile technique, X-ray with the needle or the endodontic probe in the root canal and comparing with the average tooth length.The determination of average tooth length depends on the geographic area. The current table used in practice contains the values gathered on a population group that is different than ours; the table has been made on Caucasian subjects.In conclusion, our study aims to determine the proper average values of our geographic zone, the table obtained by completing the equation of the endodontic therapy that will admit the proximity of the Romanian reality.

scholarly journals Study on dose rate distribution inside diagnostic X-ray room by using MCNP5 code

2013 ◽  
Vol 16 (4) ◽  
pp. 35-42
Author(s):  
Loan Thi Hong Truong ◽  
Thu Thi Cam Nguyen ◽  
Hien Thi Doan ◽  
Khanh Ai Tran ◽  
Dung Thi Thuy Vo ◽  
...  
Keyword(s):  
Dose Rate ◽  
Radiation Safety ◽  
Absorbed Dose ◽  
Absorbed Dose Rate ◽  
Rate Distribution ◽  
X Ray ◽  
Room Size ◽  
Exact Determination ◽  
Mcnp5 Code

In this paper, the scattering influence on image quality and radiation safety because of changing room size was studied. To estimate the radiation safety in X-ray room, the exact determination of dose rate distribution inside the room and absorbed dose rate for patient is the first task. The authors simulated the dose rate distribution inside diagnostic X-ray room at Nhi Dong hospital with using MCNP5 code. The dependence of dose rate distribution on various peak voltages of X-ray tube was also investigated in this study

scholarly journals Analytic determination of the three-dimensional distribution of dislocations using synchrotron X-ray topography

2006 ◽  
Vol 39 (1) ◽  
pp. 106-108 ◽  
Author(s):  
J. M. Yi ◽  
Y. S. Chu ◽  
T. S. Argunova ◽  
J. H. Je
Keyword(s):  
Three Dimensional ◽  
Analytic Formula ◽  
Detector Plane ◽  
X Ray ◽  
Dimensional Distribution ◽  
Distribution Of Dislocations ◽  
Symmetric Reflection ◽  
Si Wafer

A technique, using a symmetric reflectionviaazimuthal rotation of a sample, is presented for characterization of the three-dimensional distribution of dislocations in single crystals. An analytic formula is derived to transform the three-dimensional geometry of a straight dislocation into its two-dimensional projection onto the detector plane. By fitting topographs to the formula, the orientations and locations of dislocations are quantitatively determined. The dislocations in a thermally stressed Si wafer are examined as an example.

Determination of Constant Strain Gradients of Elastically Bent Crystal Using X-ray Mirage Fringes

2012 ◽  
Vol 51 ◽  
pp. 076702 ◽  
Author(s):  
Sukswat Jongsukswat ◽  
Tomoe Fukamachi ◽  
Kenji Hirano ◽  
Dongying Ju ◽  
Riichirou Negishi ◽  
...  
Keyword(s):  
Strain Gradients ◽  
X Ray ◽  
Bent Crystal

Exact determination of superlattice structures by small‐angle x‐ray diffraction method

1988 ◽  
Vol 52 (9) ◽  
pp. 742-744 ◽  
Author(s):  
M. Sugawara ◽  
M. Kondo ◽  
S. Yamazaki ◽  
K. Nakajima
Keyword(s):  
Small Angle ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Exact Determination ◽  
Superlattice Structures

Exact determination of superlattice structure by small-angle x-ray diffraction

1988 ◽  
Vol 93 (1-4) ◽  
pp. 318-322 ◽  
Author(s):  
M. Sugawara ◽  
M. Kondo ◽  
S. Yamazaki ◽  
K. Nakajima
Keyword(s):  
Small Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Superlattice Structure ◽  
Exact Determination

scholarly journals General method to calculate the elastic deformation and X-ray diffraction properties of bent crystal wafers

IUCrJ ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 102-115
Author(s):  
Ari-Pekka Honkanen ◽  
Simo Huotari
Keyword(s):  
Stress And Strain ◽  
Light Sources ◽  
X Ray Diffraction ◽  
Optical Elements ◽  
Theoretical Understanding ◽  
Strain Fields ◽  
X Ray ◽  
Bent Crystal ◽  
Bent Crystals ◽  
General Method

Toroidally and spherically bent single crystals are widely employed as optical elements in hard X-ray spectrometry at synchrotron and free-electron laser light sources, and in laboratory-scale instruments. To achieve optimal spectrometer performance, a solid theoretical understanding of the diffraction properties of such crystals is essential. In this work, a general method to calculate the internal stress and strain fields of toroidally bent crystals and how to apply it to predict their diffraction properties is presented. Solutions are derived and discussed for circular and rectangular spherically bent wafers due to their prevalence in contemporary instrumentation.

Bent-crystal monochromators for high-energy synchrotron radiation

1998 ◽  
Vol 5 (3) ◽  
pp. 699-701 ◽  
Author(s):  
Hitoshi Yamaoka ◽  
Tetsuro Mochizuki ◽  
Yoshiharu Sakurai ◽  
Hiroshi Kawata
Keyword(s):  
Finite Element ◽  
Synchrotron Radiation ◽  
Compton Scattering ◽  
Silicon Crystal ◽  
High Energy ◽  
Finite Element Analyses ◽  
X Ray ◽  
Bent Crystal ◽  
Dominant Process ◽  
Bent Crystals

Two kinds of monochromators covering the energy ranges 100–150 keV and ∼300 keV have been designed for inelastic (Compton) scattering experiments at the elliptical multipole wiggler beamline, BL08W, of SPring-8. Finite-element analyses using ANSYS for bent crystals indicate that thermal problems are not serious for the 300 keV monochromator, while an energy spread of about 10−3 for the 100–150 keV monochromator is possible in the centre of the crystal. Detailed calculations of X-ray interaction with the silicon crystal were performed. The results show that Compton scattering is a dominant process and deposits about 100 W continuously.

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