Characteristic and Continuum Fluorescence in Electron Beam X-ray Microanalysis

1999 ◽  
Vol 5 (S2) ◽  
pp. 562-563
Author(s):  
C.E. Nockolds
Keyword(s):  
Electron Beam ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Mathematical Framework ◽  
X Rays ◽  
Correction Procedure ◽  
X Ray ◽  
Exponential Term ◽  
Accurate Expression ◽  
Original Formula

Of the different aspects of electron probe microanalysis(EPMA)which were studied by Castaing during his doctorate the work on characteristic x-ray fluorescence was the most definitive. In his thesis, which was completed in 1951, Castaing established the physical and mathematical framework for a correction procedure for fluorescence which is essentially still used in EPMA today. Much of the effort since then has been in refining and improving the accuracy of the correction and extending the scope of the correction to a wider range of specimen types. The Castaing formula was developed for the case of a K x-ray from element A being excited by a K xray from element B (K-K fluorescence) and in 1965 Reed extended the range of the correction by including the K-L, L-L and L-K interactions. In the same paper Reed also introduced the expression from Green and Cosslett for the calculation of K intensities, which was believed to be more accurate than the expression used by Castaing. The original formula included a somewhat unrealistic exponential term to allow for the depth of the production of the primary x-rays and a number of workers have tried replacing this term with a more accurate expression, however, in general this has led to only small changes in the final correction. Reed also simplified the formula in order to make the calculation easier in the days before fast computers; in particular he replaced the jump ratio variable by two constants, one for the K-shell and one for the L-shell. Much later Heinrich showed that this simplification was no longer necessary and that the jump ratio could in fact be calculated directly.

Monte Carlo Simulation of Characteristic Secondary Fluorescence in Electron Probe Microanalysis of Homogeneous Samples Using the Splitting Technique

2015 ◽  
Vol 21 (3) ◽  
pp. 753-758 ◽  
Author(s):  
Mauricio Petaccia ◽  
Silvina Segui ◽  
Gustavo Castellano
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Variance Reduction ◽  
Fluorescence Enhancement ◽  
Radiation Transport ◽  
X Rays ◽  
X Ray ◽  
Secondary Fluorescence

AbstractElectron probe microanalysis (EPMA) is based on the comparison of characteristic intensities induced by monoenergetic electrons. When the electron beam ionizes inner atomic shells and these ionizations cause the emission of characteristic X-rays, secondary fluorescence can occur, originating from ionizations induced by X-ray photons produced by the primary electron interactions. As detectors are unable to distinguish the origin of these characteristic X-rays, Monte Carlo simulation of radiation transport becomes a determinant tool in the study of this fluorescence enhancement. In this work, characteristic secondary fluorescence enhancement in EPMA has been studied by using the splitting routines offered by PENELOPE 2008 as a variance reduction alternative. This approach is controlled by a single parameter NSPLIT, which represents the desired number of X-ray photon replicas. The dependence of the uncertainties associated with secondary intensities on NSPLIT was studied as a function of the accelerating voltage and the sample composition in a simple binary alloy in which this effect becomes relevant. The achieved efficiencies for the simulated secondary intensities bear a remarkable improvement when increasing the NSPLIT parameter; although in most cases an NSPLIT value of 100 is sufficient, some less likely enhancements may require stronger splitting in order to increase the efficiency associated with the simulation of secondary intensities.

Absorption Correction Curves Obtained from Measurements of the Production of X-Rays as a Function of Depth

1972 ◽  
Vol 16 ◽  
pp. 198-205
Author(s):  
J.D. Brown ◽  
L. Parobek
Keyword(s):  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
X Rays ◽  
Matrix Elements ◽  
X Ray ◽  
Absorption Correction ◽  
Correction Equations

AbstractMeasurements of x-ray production as a function of depth in a sample (ϕ(ρz) curves) are fundamental to the determination of the quantitative equations for relating x-ray intensity to composition in electron probe microanalysis. These ϕ(ρz) curves have been measured for four different voltages and a number of different tracers in aluminum, copper, silver arid gold as matrix elements. From these ϕ(ρz) curves the absorption correction curves (f(x) curves) can be calculated. Such curves have been obtained and comparison is made with the absorption correction equations of Philibert. The effect of a tilted sample on the absorption correction is also discussed.

Recent Developments in the Study of Grain Boundary Segregation by Wavelength Dispersive X-Ray Spectroscopy (WDS)

2011 ◽  
Vol 309-310 ◽  
pp. 39-44
Author(s):  
Pawel Nowakowski ◽  
Frédéric Christien ◽  
Marion Allart ◽  
René Le Gall
Keyword(s):  
Electron Beam ◽  
Fracture Surface ◽  
Grain Boundary ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Boundary Segregation ◽  
Normal Incidence ◽  
Grain Boundary Segregation ◽  
X Ray ◽  
Recent Developments

It was recently shown [1] that EMPA-WDS (Electron Probe MicroAnalysis by Wavelength Dispersive X-ray Spectroscopy) can be used to detect and to accurately quantify monolayer surface and grain boundary segregation. This paper presents the last developments of this application. It focuses on the measurement of sulphur grain boundary segregation in nickel on fractured surfaces. A special attention was paid to the quantification of the sulphur coverage, taking into account the non-normal incidence of the electron beam on a fracture surface. Sulphur grain boundary segregation kinetics was measured at 750°C in nickel to document the quantitative possibilities of the technique.

scholarly journals A Model for Characteristic X-Ray Emission in Electron Probe Microanalysis based on the Spherical Harmonic (PN) Method for Electron Transport

2021 ◽  
Author(s):  
Jonas Buenger ◽  
Silvia Richter ◽  
Manuel Torrilhon
Keyword(s):  
Monte Carlo ◽  
Electron Transport ◽  
Electron Probe Microanalysis ◽  
Spherical Harmonic ◽  
Electron Probe ◽  
Material Structure ◽  
X Rays ◽  
Minimum Entropy ◽  
Promising Alternative ◽  
X Ray

Classical k-ratio models, e.g. ZAF and phi(rho z), used in electron probe microanalysis (EPMA) assume a homogeneous or multi-layered material structure, which essentially limits the spatial resolution of EPMA to the size of the interaction volume where characteristic x-rays are produced. We present a new model for characteristic x-ray emission that avoids assumptions on the material structure to not restrict the resolution of EPMA a-priori. Our model bases on the spherical harmonic (PN) approximation of the Boltzmann equation for electron transport in continuous slowing down approximation. PN models have a simple structure, are hierarchical in accuracy and well-suited for efficient adjoint-based gradient computation, which makes our model a promising alternative to classical models in terms of improving the resolution of EPMA in the future. We present results of various test cases including a comparison of the PN model to a minimum entropy moment model as well as Monte-Carlo (MC) trajectory sampling, a comparison of PN-based k-ratios to k-ratios obtained with MC, a comparison with experimental data of electron backscattering yields as well as a comparison of PN and Monte-Carlo based on characteristic X-ray generation in a three-dimensional material probe with fine structures.

Low-Voltage Electron-Probe Microanalysis of Fe–Si Compounds Using Soft X-Rays

2013 ◽  
Vol 19 (6) ◽  
pp. 1698-1708 ◽  
Author(s):  
Phillip Gopon ◽  
John Fournelle ◽  
Peter E. Sobol ◽  
Xavier Llovet
Keyword(s):  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Low Voltage ◽  
Mass Attenuation Coefficient ◽  
X Rays ◽  
X Ray ◽  
Voltage Electron ◽  
Increased Sensitivity ◽  
Quantitative Analyses ◽  
Areas Of Interest

AbstractConventional electron-probe microanalysis has an X-ray analytical spatial resolution on the order of 1–4 μm width/depth. Many of the naturally occurring Fe–Si compounds analyzed in this study are smaller than 1 μm in size, requiring the use of lower accelerating potentials and nonstandard X-ray lines for analysis. Problems with the use of low-energy X-ray lines (soft X-rays) of iron for quantitative analyses are discussed and a review is given of the alternative X-ray lines that may be used for iron at or below 5 keV (i.e., accelerating voltage that allows analysis of areas of interest <1 μm). Problems include increased sensitivity to surface effects for soft X-rays, peak shifts (induced by chemical bonding, differential self-absorption, and/or buildup of carbon contamination), uncertainties in the mass attenuation coefficient for X-ray lines near absorption edges, and issues with spectral resolution and count rates from the available Bragg diffractors. In addition to the results from the traditionally used Fe Lα line, alternative approaches, utilizing Fe Lβ, and Fe Ll-η lines, are discussed.

Improving the Analtical Accuracy in the Analysis of Particles by Employing Low Voltage Analysis:

2000 ◽  
Vol 6 (S2) ◽  
pp. 924-925
Author(s):  
JA Small ◽  
JT Armstrong
Keyword(s):  
Electron Beam ◽  
Electron Probe ◽  
Low Voltage ◽  
X Rays ◽  
Relative Uncertainty ◽  
Particle Volume ◽  
X Ray ◽  
Uncertainty Estimates ◽  
Corrected Data ◽  
Particle Geometry

The energy of the electron beam, in conventional electron probe microanalysis, is generally in the range of 15-25 keV which provides the necessary overvoltage to excite efficiently the K and L x-ray lines for elements with atomic numbers in the range of about 5-83. One of the primary microanalytical methods for obtaining compositional information on particles is X-ray analysis in the electron probe and these same voltage criteria have been applied to the procedures developed for this purpose. The main difference in analytical procedures for bulk samples and particles is that corrections have to be applied to the particle k-ratios or calculated compositions to compensate for: 1) the penetration or scattering of electrons out of the particle volume and 2) variations in the absorption due to particle geometry of x-rays less than about 3 keV. In general, particle corrections improve the accuracy and reduce the relative uncertainty estimates from several tens of percent for uncorrected data to about 10% for corrected data.

The measurement of the fluorescence of Si K x-rays by Au M x-rays

1990 ◽  
Vol 48 (2) ◽  
pp. 198-199
Author(s):  
John A. Small ◽  
Scott A. Wight ◽  
Robert L. Myklebust ◽  
Dale E. Newbury
Keyword(s):  
Electron Beam ◽  
Electron Probe ◽  
Primary Electron ◽  
Characteristic Line ◽  
X Rays ◽  
Limited Information ◽  
Primary Electron Beam ◽  
X Ray ◽  
Image Position ◽  
Critical Excitation

The characteristic fluorescence correction is used in electron probe microanalysis to account for the x-ray intensity excited in element “a” by the x-rays from the characteristic line of another element, “b”, in the sample. Since the excited intensity is not generated by the primary electron beam, it is necessary to apply the fluorescence correction for quantitative elemental analysis. This correction can be significant particularly when element “b” is a major component of the sample and the characteristic line for element “b” is slightly higher in energy than the critical excitation energy for the excited line of element “a”.The fluorescence correction, which is used in the various analytical programs, is described in equation 1.where I'*fa/I'*pa is the ratio of the emitted “a” intensity excited by “b” x-rays to the emitted intensity excited by the primary electron beam. The various parameters in this equation are accurately known for the K x-ray lines, but only very limited information is available for the M x-ray lines.

Celebrating 40 Years of Energy Dispersive X-Ray Spectrometry in Electron Probe Microanalysis: A Historic and Nostalgic Look Back into the Beginnings

2009 ◽  
Vol 15 (6) ◽  
pp. 476-483 ◽  
Author(s):  
Klaus Keil ◽  
Ray Fitzgerald ◽  
Kurt F.J. Heinrich
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Energy Dispersive Spectrometer ◽  
Fluorescence Analysis ◽  
Energy Dispersive ◽  
X Rays ◽  
New Era ◽  
X Ray

AbstractOn February 2, 1968, R. Fitzgerald, K. Keil, and K.F.J. Heinrich published a seminal paper in Science (159, 528–530) in which they described a solid-state Si(Li) energy dispersive spectrometer (EDS) for electron probe microanalysis (EPMA) with, initially, a resolution of 600 eV. This resolution was much improved over previous attempts to use either gas-filled proportional counters or solid-state devices for EDS to detect X-rays and was sufficient, for the first time, to make EDS a practically useful technique. It ushered in a new era not only in EPMA, but also in scanning electron microscopy, analytical transmission electron microscopy, X-ray fluorescence analysis, and X-ray diffraction. EDS offers many advantages over wavelength-dispersive crystal spectrometers, e.g., it has no moving parts, covers the entire X-ray energy range of interest to EPMA, there is no defocusing over relatively large distances across the sample, and, of particular interest to those who analyze complex minerals consisting of many elements, all X-ray lines are detected quickly and simultaneously.

Electron Probe Microanalysis of REE in Eudialyte Group Minerals: Challenges and Solutions

2015 ◽  
Vol 21 (5) ◽  
pp. 1096-1113 ◽  
Author(s):  
Petya Atanasova ◽  
Joachim Krause ◽  
Robert Möckel ◽  
Inga Osbahr ◽  
Jens Gutzmer
Keyword(s):  
Electron Beam ◽  
Electron Probe Microanalysis ◽  
Inductively Coupled Plasma ◽  
Electron Probe ◽  
Beam Diameter ◽  
Eudialyte Group ◽  
X Ray ◽  
Inductively Coupled ◽  
Individual Calibration ◽  
Plasma Mass Spectrometry

AbstractAccurate quantification of the chemical composition of eudialyte group minerals (EGM) with the electron probe microanalyzer is complicated by both mineralogical and X-ray-specific challenges. These include structural and chemical variability, mutual interferences of X-ray lines, in particular of the rare earth elements, diffusive volatility of light anions and cations, and instability of EGM under the electron beam. A novel analytical approach has been developed to overcome these analytical challenges. The effect of diffusive volatility and beam damage is shown to be minimal when a square of 20×20 µm is scanned with a beam diameter of 6 µm at the fastest possible speed, while measuring elements critical to electron beam exposure early in the measurement sequence. Appropriate reference materials are selected for calibration considering their volatile content and composition, and supplementary offline overlap correction is performed using individual calibration factors. Preliminary results indicate good agreement with data from laser ablation inductively coupled plasma mass spectrometry demonstrating that a quantitative mineral chemical analysis of EGM by electron probe microanalysis is possible once all the parameters mentioned above are accounted for.

Sign in / Sign up

Export Citation Format

Share Document