scholarly journals Radiation attenuation by single-crystal diamond windows

2017 ◽  
Vol 50 (1) ◽  
pp. 76-86 ◽  
Author(s):  
M. Guthrie ◽  
C. G. Pruteanu ◽  
M.-E. Donnelly ◽  
J. J. Molaison ◽  
A. M. dos Santos ◽  
...  
Keyword(s):  
Single Crystal ◽  
Accurate Determination ◽  
Incident Beam ◽  
Neutron Radiation ◽  
Cost Effective ◽  
High Pressure Studies ◽  
Single Crystal Diamond ◽  
Diamond Anvil ◽  
Semi Empirical

As artificial diamond becomes more cost effective it is likely to see increasing use as a window for sample environment equipment used in diffraction experiments. Such windows are particularly useful as they exhibit exceptional mechanical properties in addition to being highly transparent to both X-ray and neutron radiation. A key application is in high-pressure studies, where diamond anvil cells (DACs) are used to access extreme sample conditions. However, despite their utility, an important consideration when using single-crystal diamond windows is their interaction with the incident beam. In particular, the Bragg condition will be satisfied for specific angles and wavelengths, leading to the appearance of diamond Bragg spots on the diffraction detectors but also, unavoidably, to loss of transmitted intensity of the beam that interacts with the sample. This effect can be particularly significant for energy-dispersive measurements, for example, in time-of-flight neutron diffraction work using DACs. This article presents a semi-empirical approach that can be used to correct for this effect, which is a prerequisite for the accurate determination of diffraction intensities.

Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

Determination of the barrier height of iridium with hydrogen-terminated single crystal diamond

2019 ◽  
Vol 9 (01) ◽  
pp. 165-169
Author(s):  
Yan-Feng Wang ◽  
Wei Wang ◽  
Xiaohui Chang ◽  
Juan Wang ◽  
Jiao Fu ◽  
...  
Keyword(s):  
Single Crystal ◽  
Barrier Height ◽  
Single Crystal Diamond ◽  
Image Position

Abstract

scholarly journals A Review of the Melting Curves of Transition Metals at High Pressures Using Static Compression Techniques

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 416
Author(s):  
Paraskevas Parisiades
Keyword(s):  
Transition Metals ◽  
High Pressures ◽  
Accurate Determination ◽  
Detection Methods ◽  
Melting Transition ◽  
Static Compression ◽  
Melting Curves ◽  
Strong Focus ◽  
Diamond Anvil

The accurate determination of melting curves for transition metals is an intense topic within high pressure research, both because of the technical challenges included as well as the controversial data obtained from various experiments. This review presents the main static techniques that are used for melting studies, with a strong focus on the diamond anvil cell; it also explores the state of the art of melting detection methods and analyzes the major reasons for discrepancies in the determination of the melting curves of transition metals. The physics of the melting transition is also discussed.

scholarly journals Accurate Determination of Structure Factors by Pendellosung Methods Using White Radiation

1988 ◽  
Vol 41 (3) ◽  
pp. 433 ◽  
Author(s):  
T Takama ◽  
S Sato
Keyword(s):  
Single Crystal ◽  
Accurate Determination ◽  
Diffraction Theory ◽  
Specimen Thickness ◽  
Dynamical Diffraction ◽  
Laue Spot ◽  
Exit Surface ◽  
Structure Factors ◽  
Integrated Intensity

This paper describes two experimental techniques measuring the Pendellosung beats using white radiation, developed in the authors' laboratory. The intensity of a Laue spot diffracted from a parallel-sided single crystal is successively measured at different Bragg angles, i.e. with different wavelengths. The values of structure factors are evaluated from extremum positions in the measured beats on the basis of the dynamical diffraction theory. In the first method, the integrated intensity diffracted from the whole exit surface is measured, and in the second, the measurement is made only at the centre of the Borrmann fan on the exit surface of a specimen. A discussion is given on the accuracy associated with the following origins of errors: (1) polarisation of incident white radiation, (2) measurement of specimen thickness, (3) measurement of wavelength, (4) determination of extremum positions, and (5) effect of defects in the crystal.

Diffractometric crystal centering

1999 ◽  
Vol 32 (3) ◽  
pp. 510-515 ◽  
Author(s):  
Przemyslaw Dera ◽  
Andrzej Katrusiak
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Crystal Lattice ◽  
Radiation Source ◽  
Prior Information ◽  
High Accuracy ◽  
Sample Position ◽  
Diamond Anvil ◽  
Significant Factors

A general formalism for centering a single-crystal on a four-circle diffractometer, based on the setting angles of reflections, is presented. The minimum information for the determination of crystal displacement are the diffractometer setting angles of two reciprocal vectors. The method is independent of the crystallographic system and does not require prior information about the crystal lattice. The size of the radiation source, beam divergence and homogeneity are shown to be significant factors for calculating the crystal displacement from the positions of the reflections. The method is primarily designed for samples enclosed in high-pressure diamond-anvil cells and other environments obscuring visual control of the sample position; however, high accuracy of the method in most cases allows the optical centering of the crystals to be improved, particularly for irregularly shaped samples. A procedure for retrieving true lattice dimensions, by accounting for the effect of the crystal displacement from the diffractometer center, is also presented.

scholarly journals Low-redshift lowest-metallicity star-forming galaxies in the SDSS DR14

2019 ◽  
Vol 623 ◽  
pp. A40 ◽  
Author(s):  
Y. I. Izotov ◽  
N. G. Guseva ◽  
K. J. Fricke ◽  
C. Henkel
Keyword(s):  
Accurate Determination ◽  
Sloan Digital Sky Survey ◽  
Emission Lines ◽  
Strong Line ◽  
Star Forming ◽  
Line Method ◽  
Sky Survey ◽  
Low Metallicity ◽  
Semi Empirical

We present a sample of low-redshift (z <  0.133) candidates for extremely low-metallicity star-forming galaxies with oxygen abundances 12 + log O/H <  7.4 selected from the Data Release 14 (DR14) of the Sloan Digital Sky Survey (SDSS). Three methods are used to derive their oxygen abundances. Among these methods two are based on strong [O II]λ3727 Å, [O III]λ4959 Å, and [O III]λ5007 Å emission lines, which we call strong-line and semi-empirical methods. These were applied for all galaxies. We have developed one of these methods, the strong-line method, in this paper. This method is specifically focused on the accurate determination of metallicity in extremely low-metallicity galaxies and may not be used at higher metallicities with 12 + log O/H ≳ 7.5. The third, the direct Te method, was applied for galaxies with detected [O III]λ4363 emission lines. All three methods give consistent abundances and can be used in combination or separately for selection of lowest-metallicity candidates. However, the strong-line method is preferable for spectra with a poorly detected or undetected [O III]λ4363 emission line. In total, our list of selected candidates for extremely low-metallicity galaxies includes 66 objects.

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