Quantitative Measurement of Iron-Silicides by EPMA Using the Fe Lα and Lβ X-ray Lines: A New Twist to an Old Approach

2019 ◽  
Vol 25 (3) ◽  
pp. 664-674 ◽  
Author(s):  
Aurélien Moy ◽  
John Fournelle ◽  
Anette von der Handt
Keyword(s):  
Calibration Curve ◽  
Electron Probe ◽  
Accurate Determination ◽  
Electron Transition ◽  
Electron Interaction ◽  
Transition Elements ◽  
Close Proximity ◽  
Schottky Type ◽  
Silicide Compounds ◽  
Takeoff Angle

AbstractThe recent availability of Schottky-type field emission electron microprobes provides incentive to consider analyzing micrometer-sized features. Yet, to quantify sub-micrometer-sized features, the electron interaction volume must be reduced by decreasing accelerating voltage. However, the K lines of the transition elements (e.g., Fe) then cannot be excited, and the L lines must be used. The Fe Lα1,2 line is the most intense of the L series but bonding effects change its atomic parameters because it involves a valence band electron transition. For successful traditional electron probe microanalysis, the mass absorption coefficient (MAC) must be accurately known, but the MAC of Fe Lα1,2 radiation by Fe atoms varies from one Fe-compound to another and is not well known. We show that the conventional method of measuring the MAC by an electron probe cannot be used in close proximity to absorption edges, making its accurate determination impossible. Fortunately, we demonstrate, using a set of Fe–silicide compounds, that it is possible to derive an accurate calibration curve, for a given accelerating voltage and takeoff angle, which can be used to quantify Fe in Fe–silicide compounds. The calibration curve can be applied to any spectrometer without calibration and gives accurate quantification results.

scholarly journals Elastic Electron Scattering from Methane Molecule in the Energy Range from 50–300 eV

2021 ◽  
Vol 22 (2) ◽  
pp. 647
Author(s):  
Jelena Vukalović ◽  
Jelena B. Maljković ◽  
Karoly Tökési ◽  
Branko Predojević ◽  
Bratislav P. Marinković
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Electron Gun ◽  
Methane Molecule ◽  
Edge Plasma ◽  
Electron Interaction ◽  
Outer Planet ◽  
Elastic Electron

Electron interaction with methane molecule and accurate determination of its elastic cross-section is a demanding task for both experimental and theoretical standpoints and relevant for our better understanding of the processes in Earth’s and Solar outer planet atmospheres, the greenhouse effect or in plasma physics applications like vapor deposition, complex plasma-wall interactions and edge plasma regions of Tokamak. Methane can serve as a test molecule for advancing novel electron-molecule collision theories. We present a combined experimental and theoretical study of the elastic electron differential cross-section from methane molecule, as well as integral and momentum transfer cross-sections in the intermediate energy range (50–300 eV). The experimental setup, based on a crossed beam technique, comprising of an electron gun, a single capillary gas needle and detection system with a channeltron is used in the measurements. The absolute values for cross-sections are obtained by relative-flow method, using argon as a reference. Theoretical results are acquired using two approximations: simple sum of individual atomic cross-sections and the other with molecular effect taken into the account.

scholarly journals Determining Girard Form Class in Central Hardwoods

1997 ◽  
Vol 14 (4) ◽  
pp. 202-206 ◽  
Author(s):  
John C. Rennie ◽  
Jack D. Leake
Keyword(s):  
Direct Measurement ◽  
Accurate Determination ◽  
Tree Form ◽  
Form Class ◽  
Wide Range ◽  
Close Proximity ◽  
Wedge Prism ◽  
The Cost ◽  
Volume Estimates

Abstract Girard form class is widely used to describe tree form. Tree volume estimates change about 3% per unit change of Girard form class (Mesavage and Girard 1946). Hardwoods growing in close proximity have been observed to have a wide range in Girard form class. Accurate determination of Girard form class can therefore be important in getting accurate estimates of hardwood timber volume. However, the cost of estimating Girard form class for every tree being measured in the stand would be prohibitively expensive. Thus, estimation of average Girard form class for a stand is considered here. Three instruments used to estimate Girard form class—a Wheeler pentaprism optical caliper, a wedge prism, and a Spiegel relaskop—were compared to direct measurement. Number of sample trees to achieve desired half-widths of the confidence interval of ±1 and ±1 1/2 units of Girard form class was calculated for each method. Direct measurement requires the fewest trees to achieve the desired results. However, it requires considerably more time per tree than any of the instruments tested. The Wheeler pentaprism requires only a few more trees than direct measurement, and considerably fewer trees than either the wedge prism or the Spiegel relaskop. Use of all three instruments is hindered when understory vegetation obscures the top of the first log. North. J. Appl. For. 14(4):202-206.

Two varieties of lithiophorite in some Australian deposits

1984 ◽  
Vol 48 (348) ◽  
pp. 383-388 ◽  
Author(s):  
J. Ostwald
Keyword(s):  
Mixed Layer ◽  
Electron Probe ◽  
Marked Change ◽  
Alumina Content ◽  
Transition Elements ◽  
Zn Content ◽  
Cu And Zn

Abstract Electron probe microanalyses carried out on thirty areas of lithiophorite (Al,Li)MnO2(OH)2 from five Australian localities indicate wide variations in its Ni, Co, Cu, and Zn content. The concentration of these elements varies inversely with the alumina content, though there is a marked change in their concentration at 18% alumina, suggesting the existence of two varieties of lithiophorite with differing concentration of transition elements. EPMA line scans also indicate definite changes in Co content in lithiophorite grains less than 0.2 mm in dimension. The variations in alumina and transition elements may be explained if lithiophorite is considered to be an irregular mixed-layer-lattice intergrowth of pure lithiophorite with members of the recently discovered asbolane-type minerals.

scholarly journals Implementation and experimental evaluation of Mega-voltage fan-beam CT using a linear accelerator

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Hao Gong ◽  
Shengzhen Tao ◽  
Justin D. Gagneur ◽  
Wei Liu ◽  
Jiajian Shen ◽  
...  
Keyword(s):  
Calibration Curve ◽  
Linear Accelerator ◽  
Prediction Accuracy ◽  
Accurate Determination ◽  
Projection Data ◽  
Ct Number ◽  
Radiation Level ◽  
Artifact Correction ◽  
Imaging Device ◽  
Standard Clinical Practice

Abstract Background Mega-voltage fan-beam Computed Tomography (MV-FBCT) holds potential in accurate determination of relative electron density (RED) and proton stopping power ratio (SPR) but is not widely available. Objective To demonstrate the feasibility of MV-FBCT using a medical linear accelerator (LINAC) with a 2.5 MV imaging beam, an electronic portal imaging device (EPID) and multileaf collimators (MLCs). Methods MLCs were used to collimate MV beam along z direction to enable a 1 cm width fan-beam. Projection data were acquired within one gantry rotation and preprocessed with in-house developed artifact correction algorithms before the reconstruction. MV-FBCT data were acquired at two dose levels: 30 and 60 monitor units (MUs). A Catphan 604 phantom was used to evaluate basic image quality. A head-sized CIRS phantom with three configurations of tissue-mimicking inserts was scanned and MV-FBCT Hounsfield unit (HU) to RED calibration was established for each insert configuration using linear regression. The determination coefficient ($${R}^{2}$$ R 2 ) was used to gauge the accuracy of HU-RED calibration. Results were compared with baseline single-energy kilo-voltage treatment planning CT (TP-CT) HU-RED calibration which represented the current standard clinical practice. Results The in-house artifact correction algorithms effectively suppressed ring artifact, cupping artifact, and CT number bias in MV-FBCT. Compared to TP-CT, MV-FBCT was able to improve the prediction accuracy of the HU-RED calibration curve for all three configurations of insert materials, with $${R}^{2}$$ R 2 > 0.9994 and $${R}^{2}$$ R 2 < 0.9990 for MV-FBCT and TP-CT HU-RED calibration curves of soft-tissue inserts, respectively. The measured mean CT numbers of blood-iodine mixture inserts in TP-CT drastically deviated from the fitted values but not in MV-FBCT. Reducing the radiation level from 60 to 30 MU did not decrease the prediction accuracy of the MV-FBCT HU-RED calibration curve. Conclusion We demonstrated the feasibility of MV-FBCT and its potential in providing more accurate RED estimation.

Monte-Carlo simulation of intensity ratio Is/Ic from substrate and film to determine the film thickness

1988 ◽  
Vol 46 ◽  
pp. 972-973
Author(s):  
Jin Guangxiang ◽  
Li Jianlin ◽  
Xu Li ◽  
Wu Ziqin
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Film Thickness ◽  
Electron Scattering ◽  
Calibration Curve ◽  
Intensity Ratio ◽  
Electron Probe ◽  
Monte Carlo Calculation ◽  
X Ray

The methods of thickness of film on substrate by electron probe have been published in literatures. It may be carried out simply by constructing a calibration curve from x-ray intensity measurments made on a series of films with known thickness on substrate.Sweeney et al. obtained a calibration curve based on a calcula- tied x-ray Ø(p z). As the calculation of Ø(p z) is difficult, Cockett and Davis, proposed using the experimental Ø(p z) of Castaing and Descamps. Bishop and Poole utilised Ø(p z) established by Monte-Carlo calculation for calibration curve.Huchings' method took into account the different electron scattering and absorption in the film on substrate and the bulk standard.Reuter et al., constructing a curve of Ic/Ib (Ic, intensity of the film on substrate; Ib, intensity of bulk standard) versus electron accelerating voltage E, exterpolate the curve so that Ic/Ib equals to 1, the excited x-ray depth obtained is just equal to the thickness of the film. The thickness of the film can be obtained by the use of an appropiate equation of excited x-ray depth.

Solving the iron quantification problem in low-kV EPMA: An essential step toward improved analytical spatial resolution in electron probe microanalysis—Olivines

2019 ◽  
Vol 104 (8) ◽  
pp. 1131-1142 ◽  
Author(s):  
Aurélien Moy ◽  
John H. Fournelle ◽  
Anette von der Handt
Keyword(s):  
Melt Inclusions ◽  
Accurate Solution ◽  
Electron Interaction ◽  
X Rays ◽  
Transition Elements ◽  
X Ray ◽  
Iron Quantification ◽  
Accurate Quantitative Analysis ◽  
First Time ◽  
The Relationship

AbstractThe relatively recent entry of field emission electron microprobes into the field of microanalysis provides another tool for the study of small features of interest (e.g., mineral and melt inclusions, ex-solution lamellae, grain boundary phases, high-pressure experimental charges). However, the critical limitation for accurate quantitative analysis of these submicrometer- to micrometer-sized features is the relationship between electron beam potential and electron scattering within the sample. To achieve submicrometer analytical volumes from which X-rays are generated, the beam accelerating voltage must be reduced from 15–20 to ≤10 kV (often 5 to 7 kV) to reduce the electron interaction volume from ~3 to ~0.5 μm in common geological materials. At these low voltages, critical Kα X-ray lines of transition elements such as Fe are no longer generated, so L X-ray lines must be used. However, applying the necessary matrix corrections to these L lines is complicated by bonding and chemical peak shifts for soft X-ray transitions such as those producing the FeLα X-ray line. It is therefore extremely challenging to produce accurate values for Fe concentration with this approach. Two solutions have been suggested, both with limitations. We introduce here a new, simple, and accurate solution to this problem, using the common mineral olivine as an example. We also introduce, for the first time, olivine results from a new analytical device, the Extended Range Soft X-ray Emission Spectrometer.

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