scholarly journals Absolute Luminescence Efficiency of Europium-Doped Calcium Fluoride (CaF2:Eu) Single Crystals under X-ray Excitation

Crystals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 234 ◽  
Author(s):  
Christos Michail ◽  
Nektarios Kalyvas ◽  
Athanasios Bakas ◽  
Konstantinos Ninos ◽  
Ioannis Sianoudis ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Single Crystal ◽  
Single Crystals ◽  
Optical Sensors ◽  
Calcium Fluoride ◽  
X Rays ◽  
Silicon Photomultipliers ◽  
X Ray ◽  
Luminescence Efficiency ◽  
Radiation Sensors

The absolute luminescence efficiency (AE) of a calcium fluoride (CaF2:Eu) single crystal doped with europium was studied using X-ray energies met in general radiography. A CaF2:Eu single crystal with dimensions of 10 × 10 × 10 mm3 was irradiated by X-rays. The emission light photon intensity of the CaF2:Eu sample was evaluated by measuring AE within the X-ray range from 50 to 130 kV. The results of this work were compared with data obtained under similar conditions for the commercially employed medical imaging modalities, Bi4Ge3O12 and Lu2SiO5:Ce single crystals. The compatibility of the light emitted by the CaF2:Eu crystal, with the sensitivity of optical sensors, was also examined. The AE of the 10 × 10 × 10 mm3 CaF2:Eu crystal peaked in the range from 70 to 90 kV (22.22 efficiency units; E.U). The light emitted from CaF2:Eu is compatible with photocathodes, charge coupled devices (CCD), and silicon photomultipliers, which are used as radiation sensors in medical imaging systems. Considering the AE results in the examined energies, as well as the spectral compatibility with various photodetectors, a CaF2:Eu single crystal could be considered for radiographic applications, including the detection of charged particles and soft gamma rays.

scholarly journals Luminescence Efficiency of Cadmium Tungstate (CdWO4) Single Crystal for Medical Imaging Applications

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 429
Author(s):  
Christos Michail ◽  
Vaia Koukou ◽  
Niki Martini ◽  
George Saatsakis ◽  
Nektarios Kalyvas ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Single Crystal ◽  
Optical Sensors ◽  
Light Output ◽  
High Energy ◽  
Published Data ◽  
X Rays ◽  
Cadmium Tungstate ◽  
X Ray ◽  
Luminescence Efficiency

Background: In this study, the light output of a cadmium tungstate (CdWO4) single crystal was measured under various X-ray radiographic energies. Methods: A CdWO4 single crystal (10 × 10 × 10 mm3) was exposed to X-rays in the 50–130 kVp range. Measurements were evaluated against published data for single crystals of equal dimensions (CaF2:Eu and Lu3Al5O12:Ce). Since the crystal was examined for application in medical imaging detectors, the emitted optical spectrum was classified with respect to the spectral compatibility of numerous commercial optical sensors. Results: The luminescence efficiency (LE) was found to constantly increase with X-ray energy and was higher than that of CaF2:Eu for energies above 90 kVp. However, the efficiency of the previously published Lu3Al5O12:Ce was found to be constantly higher than that of CdWO4. The light emitted from CdWO4 can be optimally detected by certain charge-coupled devices (CCDs), amorphous silicon photodiodes, and photocathodes. Conclusions: The high density (7.9 g/cm3) of CdWO4 and the luminescence signal of this material make it suitable for medical imaging (such as dual energy), high-energy physics or for applications of scintillators in harsh environments.

scholarly journals On the structure of multilayers. Part I

1940 ◽  
Vol 176 (967) ◽  
pp. 534-542 ◽  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Angle Of Incidence ◽  
X Rays ◽  
Ethyl Stearate ◽  
X Ray ◽  
Entire Thickness ◽  
Long Chain

X -ray and microscopic examinations of multilayers of certain long-chain esters deposited on transparent bases have been made. An X -ray photograph of a stationary multilayer of ethyl stearate is apparently identical with that obtained by rotating a single crystal of β -ethyl stearate about the long axis of the cell. The spots previously observed on oscillation photographs of multilayers of ethyl stearate are in reality parts of circles, successive arcs of which appear on increasing the angle of incidence of the X -rays on the multilayer. These facts reveal that the multilayer consists of microcrystals all oriented with one axis in common, this axis being the normal to the surface of the multilayer. The single crystals appear to have grown without interruption throughout the entire thickness of the multilayer, which in these investigations was about 1000 mol. thick.

Asymmetric Crystals Re-Visited

1987 ◽  
Vol 31 ◽  
pp. 395-401
Author(s):  
Michael A. Short ◽  
Stephen E. Robie
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Lithium Fluoride ◽  
X Rays ◽  
X Ray ◽  
Intense Beam

An asymmetrically cut single crystal is, generally, a large flat X-ray monochromating crystal whose principal surface has been cut an angle to the diffracting planes being utilised.The use of such a crystal was suggested by Stephen and Barnes in 1935 as a means of obtaining a narrow intense beam of monochromatic X-rays. Fankuchen was first to demonstrate this effect experimentally. A number of symmetrically cut mosaic single crystals, including lithium fluoride, was studied by Evans, Hirsch and Kellar and by Gay, Hirsch and Kellar in the beam condensing (beam narrowing) mode only.

Some Developments in the X-ray Analysis of Single-Crystals

1927 ◽  
Vol 23 (5) ◽  
pp. 561-577
Author(s):  
R. L. Aston
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Incident Beam ◽  
X Rays ◽  
Surface Layers ◽  
X Ray ◽  
Axis Of Rotation ◽  
Component Wave

A method has been devised by Dr Alex Müller for determining the orientation of a single-crystal of metal by photographic measurement of the reflection of characteristic X-rays from surface layers. The incident beam passes perpendicularly through an axis of rotation around which the crystal is turned until a reflection is obtained with one of the component wave-lengths of the X-rays.

scholarly journals X-ray diffraction using focused-ion-beam-prepared single crystals

2020 ◽  
Vol 53 (3) ◽  
pp. 614-622
Author(s):  
Tina Weigel ◽  
Claudia Funke ◽  
Matthias Zschornak ◽  
Thomas Behm ◽  
Hartmut Stöcker ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Preparation Technique ◽  
X Rays ◽  
X Ray Diffraction ◽  
Electron Densities ◽  
X Ray ◽  
Absorption Correction

High-quality single-crystal X-ray diffraction measurements are a prerequisite for obtaining precise and reliable structure data and electron densities. The single crystal should therefore fulfill several conditions, of which a regular defined shape is of particularly high importance for compounds consisting of heavy elements with high X-ray absorption coefficients. The absorption of X-rays passing through a 50 µm-thick LiNbO3 crystal can reduce the transmission of Mo Kα radiation by several tens of percent, which makes an absorption correction of the reflection intensities necessary. In order to reduce ambiguities concerning the shape of a crystal, used for the necessary absorption correction, a method for preparation of regularly shaped single crystals out of large samples is presented and evaluated. This method utilizes a focused ion beam to cut crystals with defined size and shape reproducibly and carefully without splintering. For evaluation, a single-crystal X-ray diffraction study using a laboratory diffractometer is presented, comparing differently prepared LiNbO3 crystals originating from the same macroscopic crystal plate. Results of the data reduction, structure refinement and electron density reconstruction indicate qualitatively similar values for all prepared crystals. Thus, the different preparation techniques have a smaller impact than expected. However, the atomic coordinates, electron densities and atomic charges are supposed to be more reliable since the focused-ion-beam-prepared crystal exhibits the smallest extinction influences. This preparation technique is especially recommended for susceptible samples, for cases where a minimal invasive preparation procedure is needed, and for the preparation of crystals from specific areas, complex material architectures and materials that cannot be prepared with common methods (breaking or grinding).

Improvement of Compact X-Rays Source Using Uniaxially Polarized LiNbO3 Single Crystal

2010 ◽  
Vol 445 ◽  
pp. 43-46 ◽  
Author(s):  
Yang Guan ◽  
Shinji Fukao ◽  
Kazuyuki Ito ◽  
Yoshikazu Nakanishi ◽  
Yuuki Sato ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Electric Field ◽  
Single Crystal ◽  
Single Crystals ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
X Rays ◽  
X Ray ◽  
Radiation Equipment ◽  
The Stability

X-ray radiation using pyroelectric crystal is intermittent and the X-ray intensity is low and unstable compared with a conventional X-ray radiation method, such as X-ray tube. It is expected that the X-ray intensity becomes stable if electric field intensity and supply of electron are stable. In this study, to use X-ray radiation equipment as an electron source, tandem-type X-ray radiation equipment which is composed of two LiNbO3 single crystals polarized in a z-axis is proposed. When the temperature gradient for each crystal was the same, the X-ray intensity became approximately 6 times higher at a maximum. When the temperature gradient for each crystal was reversed, the period of X-ray radiation became approximately two times longer and the X-ray intensity became approximately 20 times higher at a maximum. Moreover, the stability of X-ray radiation for the repetition of temperature could be improved.

scholarly journals Growth of sillenite Bi12FeO20 single crystals: structural, thermal, optical, photocatalytic features and first principle calculations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Durga Sankar Vavilapalli ◽  
Ambrose A. Melvin ◽  
F. Bellarmine ◽  
Ramanjaneyulu Mannam ◽  
Srihari Velaga ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Photoelectron Spectroscopy ◽  
Diffraction Method ◽  
Lattice Parameter ◽  
First Principle ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Principle Calculations ◽  
Photodegradation Efficiency

AbstractIdeal sillenite type Bi12FeO20 (BFO) micron sized single crystals have been successfully grown via inexpensive hydrothermal method. The refined single crystal X-ray diffraction data reveals cubic Bi12FeO20 structure with single crystal parameters. Occurrence of rare Fe4+ state is identified via X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The lattice parameter (a) and corresponding molar volume (Vm) of Bi12FeO20 have been measured in the temperature range of 30–700 °C by the X-ray diffraction method. The thermal expansion coefficient (α) 3.93 × 10–5 K−1 was calculated from the measured values of the parameters. Electronic structure and density of states are investigated by first principle calculations. Photoelectrochemical measurements on single crystals with bandgap of 2 eV reveal significant photo response. The photoactivity of as grown crystals were further investigated by degrading organic effluents such as Methylene blue (MB) and Congo red (CR) under natural sunlight. BFO showed photodegradation efficiency about 74.23% and 32.10% for degrading MB and CR respectively. Interesting morphology and microstructure of pointed spearhead like BFO crystals provide a new insight in designing and synthesizing multifunctional single crystals.

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

Calcium Carbodiimide Compounds Revisited – Syntheses, Single Crystal Structure Determination and Vibrational Spectra of Ca11N6[CN2]2, Ca4N2[CN2] and Ca[CN2]

2008 ◽  
Vol 63 (5) ◽  
pp. 530-536 ◽  
Author(s):  
Olaf Reckeweg ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Raman Spectrum ◽  
Single Crystal ◽  
Single Crystals ◽  
Vibrational Spectra ◽  
Structure Determination ◽  
X Ray ◽  
Characteristic Features ◽  
Reported Data ◽  
Correct Data

Single crystals of Ca11N6[CN2]2 (dark red needles, tetragonal, P42/mnm (no. 136), a = 1456.22(5), and c = 361.86(2) pm, Z = 2), Ca4N2[CN2] (transparent yellow needles, orthorhombic, Pnma (no. 62), a = 1146.51(11), b = 358.33(4), and c = 1385.77(13) pm, Z = 4) and Ca[CN2] (transparent, colorless, triangular plates, rhombohedral, R3̅m (no. 166), a = 369.00(3), and c = 1477.5(3) pm, Z = 3) were obtained by the reaction of Na2[CN2], CaCl2 and Ca3N2 (if demanded by stoichiometry) in arc-welded Ta ampoules at temperatures between 1200 - 1400 K. Their crystal structures were re-determined by means of single crystal X-ray structure analyses. Additionally, the Raman spectra were recorded on these same single crystals, whereas the IR spectra were obtained with the KBr pellet technique. The title compounds exhibit characteristic features for carbodiimide units with D∞h symmetry (d(C-N) = 121.7 - 123.8 pm and ∡ (N-C-N) = 180°). The vibrational frequencies of these units are in the expected range (Ca11N6[CN2]2: νs = 1230, νs = 2008; δ = 673/645/624 cm−1; Ca4N2[CN2]: νs = 1230, νs = 1986; δ = 672/647 cm−1; Ca[CN2]: νs = 1274, νs = 2031, δ = 668 cm−1). The structural results are more precise than the previously reported data, and with the newly attained Raman spectrum of Ca11N6[CN2]2 we correct data reported earlier.

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