Tomodensitométrie axiale: relation entre l'intensité tomographique et la densité de la matière

1994 ◽  
Vol 31 (2) ◽  
pp. 426-434 ◽  
Author(s):  
X. Boespflug ◽  
N. Ross ◽  
B. Long ◽  
J. F. Dumais
Keyword(s):  
Compton Scattering ◽  
Atomic Number ◽  
Computer Tomography ◽  
Empirical Model ◽  
Linear Correlation ◽  
X Rays ◽  
Photoelectric Absorption ◽  
High Atomic Number ◽  
Liquid Samples

The calibration of an axial tomodensitometer, used in sedimentology, was carried out on minerals and liquid samples. This study, taking into consideration the interactions between X rays and matter, revealed (i) a good correlation between the density of samples containing elements with low atomic number, which undergo only Compton scattering, and the intensity readings obtained by computer tomography and (ii) readings higher than predicted by linear correlation for samples containing elements with high atomic number, which undergo both Compton scattering and photoelectric absorption. An empirical model is used to correct the readings and correlate them with the density.

scholarly journals The Auger effect in xenon and krypton

1937 ◽  
Vol 158 (893) ◽  
pp. 46-54 ◽  
Keyword(s):  
Atomic Number ◽  
Wave Length ◽  
Short Wave ◽  
X Rays ◽  
Expansion Chamber ◽  
High Atomic Number ◽  
Short Wave Length ◽  
Relativistic Treatment ◽  
Number Curve ◽  
Auger Effect

In an earlier paper an account was given of a determination of the efficiency of emission of K series radiations from argon atoms ionized in the K shell. This efficiency, usually termed the K yield, was calculated from a statistical count of ordinary K photoelectron tracks and Auger pair tracks observed in a Wilson expansion chamber. These experiments have been extended to xenon and krypton, and the present paper describes the measurement of the K yields of these two gases. Determinations of the K yields for elements of high atomic number with the cloud expansion chamber should be of especial value, as other methods which depend on the measurement of X-ray energy by ionization currents encounter considerable difficulties owing to the increasing importance of scattering with short wave-length X-rays. The need for new measurements for the heavier elements has been emphasized recently by the striking divergence between the results of two extensive series of measurements, one due to Berkey and the other to Arends, both of whom used an ionization method. Berkey found a well-defined maximum in the K yield-atomic number curve in the neighbourhood of atomic number 44 after which the K yield suddenly decreased with increasing atomic number, an effect which is in direct contradiction with the experiments of Arends and existing theory. In connexion with the latter, too, measurements of the K yields for elements of high atomic number are of importance as calculations made recently by Massey and Burhop show that a relativistic treatment of the Auger effect yields rather lower values of the K yield for the higher atomic numbers than was expected by Burhop from his non-relativistic treatment.

X-Ray Fluorescence of Intermediate- to High-Atomic-Number Elements Using Polarized X Rays

1981 ◽  
Vol 25 ◽  
pp. 75-79 ◽  
Author(s):  
R. B. Strittmatter
Keyword(s):  
Atomic Number ◽  
Matrix Effects ◽  
Low Energy ◽  
Detection Sensitivity ◽  
Excitation Source ◽  
X Rays ◽  
X Ray ◽  
High Atomic Number ◽  
Increase In Accuracy

The use of polarized x rays as the excitation source for x-ray fluorescence (XRF) measurements has been shown to significantly improve signal-to-background ratios. However, previous studies on polarized x rays applied to XRF techniques have concentrated on low-energy fluoresced x rays (<30 keV). In many cases strong matrix effects exist or the analyte is encased by a material that strongly attenuates low-energy x rays. These situations may preclude accurate assays based on L x-ray detection, and techniques based on the detection of higher energy K x rays may be more suitable because of the increased penetrability of higher energy x rays. The measurements and calculations reported in this work were made to assess the improvement in signal-to-background ratios and the increase in accuracy and detection sensitivity achievable by using polarized x rays as the excitation source for fluoresced x rays having energies between 25 and 110 keV.

The Photoelectric Absorption of Gamma Rays

1931 ◽  
Vol 27 (1) ◽  
pp. 103-112 ◽  
Author(s):  
L. H. Gray
Keyword(s):  
Absorption Coefficient ◽  
Atomic Number ◽  
Gamma Rays ◽  
Wave Length ◽  
X Rays ◽  
Photoelectric Absorption ◽  
Empirical Law ◽  
Γ Rays ◽  
Image Position

No satisfactory formula has so far been derived theoretically for the photoelectric absorption of X-rays and γ-rays. The empirical lawhas hitherto been generally accepted as giving approximately the variation of the photoelectric absorption coefficient per electron, with atomic numberZand wave length λ for X-rays of wave length greater than 100 X.U., and the validity of this law has often been assumed for γ-rays also.

Contribution of x-ray total reflection to the background intensity in EPMA

1990 ◽  
Vol 48 (2) ◽  
pp. 202-203
Author(s):  
Werner P. Rehbach ◽  
Peter Karduck
Keyword(s):  
Atomic Number ◽  
Target Material ◽  
Total Reflection ◽  
Background Intensity ◽  
X Rays ◽  
Characteristic Radiation ◽  
X Ray

In the EPMA of soft x rays anomalies in the background are found for several elements. In the literature extremely high backgrounds in the region of the OKα line are reported for C, Al, Si, Mo, and Zr. We found the same effect also for Boron (Fig. 1). For small glancing angles θ, the background measured using a LdSte crystal is significantly higher for B compared with BN and C, although the latter are of higher atomic number. It would be expected, that , characteristic radiation missing, the background IB (bremsstrahlung) is proportional Zn by variation of the atomic number of the target material. According to Kramers n has the value of unity, whereas Rao-Sahib and Wittry proposed values between 1.12 and 1.38 , depending on Z, E and Eo. In all cases IB should increase with increasing atomic number Z. The measured values are in discrepancy with the expected ones.

scholarly journals Is Micro X-ray Computer Tomography a Suitable Non-Destructive Method for the Characterisation of Dental Materials?

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1271
Author(s):  
Andreas Koenig ◽  
Leonie Schmohl ◽  
Johannes Scheffler ◽  
Florian Fuchs ◽  
Michaela Schulz-Siegmund ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Computer Tomography ◽  
Mechanical Performance ◽  
Dental Materials ◽  
Three Dimensional ◽  
X Rays ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Multiple Measurements ◽  
High Doses

The aim of the study was to investigate the effect of X-rays used in micro X-ray computer tomography (µXCT) on the mechanical performance and microstructure of a variety of dental materials. Standardised bending beams (2 × 2 × 25 mm3) were forwarded to irradiation with an industrial tomograph. Using three-dimensional datasets, the porosity of the materials was quantified and flexural strength was investigated prior to and after irradiation. The thermal properties of irradiated and unirradiated materials were analysed and compared by means of differential scanning calorimetry (DSC). Single µXCT measurements led to a significant decrease in flexural strength of polycarbonate with acrylnitril-butadien-styrol (PC-ABS). No significant influence in flexural strength was identified for resin-based composites (RBCs), poly(methyl methacrylate) (PMMA), and zinc phosphate cement (HAR) after a single irradiation by measurement. However, DSC results suggest that changes in the microstructure of PMMA are possible with increasing radiation doses (multiple measurements, longer measurements, higher output power from the X-ray tube). In summary, it must be assumed that X-ray radiation during µXCT measurement at high doses can lead to changes in the structure and properties of certain polymers.

scholarly journals Effect on Compton Scattering Spectra by Hermite–Gaussian Light

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 650
Author(s):  
Akane Agui ◽  
Hiroshi Sakurai ◽  
Naruki Tsuji ◽  
Haruka Ito ◽  
Kiyofumi Nitta
Keyword(s):  
Compton Scattering ◽  
X Rays ◽  
Harmonic Order ◽  
X Ray ◽  
Scattering Spectra

In this study, we measured the Compton scattering spectra of Al, Ag and Au metals changing the harmonic order of X-rays from an undulator. The width of the Compton scattered X-ray spectrum changed depending on the harmonic order of X-rays. This indicates that Compton scattering spectra shape reflects a momentum perpendicular to the traveling direction in Hermite–Gaussian (HG) light.

Compton Scattering of X-Rays in Crystals

1958 ◽  
Vol 30 (1) ◽  
pp. 232-234 ◽  
Author(s):  
H. CURIEN
Keyword(s):  
Compton Scattering ◽  
X Rays
Sign in / Sign up

Export Citation Format

Share Document