Correction for Non-Linearity of Proportional Counter Systems in Electron Probe X-Ray Microanalysis

1965 ◽  
Vol 9 ◽  
pp. 208-220 ◽  
Author(s):  
Kurt F. J. Heinrich ◽  
Donald Vieth ◽  
Harvey Yakowitz
Keyword(s):  
Theoretical Basis ◽  
Electron Probe ◽  
Dead Time ◽  
Pulse Height ◽  
The Other ◽  
Time Effects ◽  
X Ray ◽  
Electron Probe Microanalyzer ◽  
Intensity Measurements

AbstractWhile the theoretical basis for the correction of non-linearity of detector systems is well known, methods for the determination of dead-time effects must be adapted to electron probe microanalyzer systems. Two such methods, one employing both X-ray and current measurements and the other employing simultaneous X-ray measurements on two spectrometers, are described. The effect of pulse-height shrinkage at high counting rates on the linearity of the detector system is discussed. When the proposed corrections for the dead-time of X-ray detector systems employing proportional counters are applied to the X-ray intensity measurements obtained with the electron probe microanalyzer, count rates as high as 50,000 counts/sec can be used.

Microchemical imaging in biomedical research

1992 ◽  
Vol 50 (2) ◽  
pp. 1118-1119
Author(s):  
P. Ingram
Keyword(s):  
Data Analysis ◽  
Electron Probe ◽  
The Other ◽  
X Ray ◽  
Cell Element ◽  
Physiological Information ◽  
Functional States ◽  
Elemental Maps ◽  
Electron Energy Loss ◽  
Secondary Ion

It is well established that unique physiological information can be obtained by rapidly freezing cells in various functional states and analyzing the cell element content and distribution by electron probe x-ray microanalysis. (The other techniques of microanalysis that are amenable to imaging, such as electron energy loss spectroscopy, secondary ion mass spectroscopy, particle induced x-ray emission etc., are not addressed in this tutorial.) However, the usual processes of data acquisition are labor intensive and lengthy, requiring that x-ray counts be collected from individually selected regions of each cell in question and that data analysis be performed subsequent to data collection. A judicious combination of quantitative elemental maps and static raster probes adds not only an additional overall perception of what is occurring during a particular biological manipulation or event, but substantially increases data productivity. Recent advances in microcomputer instrumentation and software have made readily feasible the acquisition and processing of digital quantitative x-ray maps of one to several cells.

Reduction of Potassium in Kidney Proximal Tubules to Aid in Electron Probe X-Ray Microanalysis of Calcium

1985 ◽  
Vol 43 ◽  
pp. 474-475
Author(s):  
A. LeFurgey ◽  
P. Ingram ◽  
L.J. Mandel
Keyword(s):  
Smooth Muscle ◽  
Proximal Tubule ◽  
Electron Probe ◽  
Clinical Applications ◽  
Proximal Tubules ◽  
Rabbit Kidney ◽  
Target Cells ◽  
X Ray ◽  
Freeze Dried

For quantitative determination of subcellular Ca distribution by electron probe x-ray microanalysis, decreasing (and/or eliminating) the K content of the cell maximizes the ability to accurately separate the overlapping K Kß and Ca Kα peaks in the x-ray spectra. For example, rubidium has been effectively substituted for potassium in smooth muscle cells, thus giving an improvement in calcium measurements. Ouabain, a cardiac glycoside widely used in experimental and clinical applications, inhibits Na-K ATPase at the cell membrane and thus alters the cytoplasmic ion (Na,K) content of target cells. In epithelial cells primarily involved in active transport, such as the proximal tubule of the rabbit kidney, ouabain rapidly (t1/2= 2 mins) causes a decrease2 in intracellular K, but does not change intracellular total or free Ca for up to 30 mins. In the present study we have taken advantage of this effect of ouabain to determine the mitochondrial and cytoplasmic Ca content in freeze-dried cryosections of kidney proximal tubule by electron probe x-ray microanalysis.

Energy-dependent dead-time correction in digital pulse processors applied to silicon drift detector's X-ray spectra

2018 ◽  
Vol 25 (2) ◽  
pp. 484-495 ◽  
Author(s):  
Suelen F. Barros ◽  
Vito R. Vanin ◽  
Alexandre A. Malafronte ◽  
Nora L. Maidana ◽  
Marcos N. Martins
Keyword(s):  
Dead Time ◽  
Pulse Height ◽  
Height Distribution ◽  
Pulse Height Distribution ◽  
Dead Time Correction ◽  
Time Model ◽  
X Ray ◽  
Digital Pulse ◽  
Analytical Correction ◽  
Energy Dependent

Dead-time effects in X-ray spectra taken with a digital pulse processor and a silicon drift detector were investigated when the number of events at the low-energy end of the spectrum was more than half of the total, at counting rates up to 56 kHz. It was found that dead-time losses in the spectra are energy dependent and an analytical correction for this effect, which takes into account pulse pile-up, is proposed. This and the usual models have been applied to experimental measurements, evaluating the dead-time fraction either from the calculations or using the value given by the detector acquisition system. The energy-dependent dead-time model proposed fits accurately the experimental energy spectra in the range of counting rates explored in this work. A selection chart of the simplest mathematical model able to correct the pulse-height distribution according to counting rate and energy spectrum characteristics is included.

Measurement And Simulation Of X-Ray Emission From Multilayered Structures In Electron Probe Microanalysis.

1999 ◽  
Vol 5 (S2) ◽  
pp. 78-79
Author(s):  
C. Merlet ◽  
X. Llovet ◽  
F. Salvat
Keyword(s):  
Electron Probe ◽  
Numerical Models ◽  
Carbon Layer ◽  
Single Element ◽  
Surface Ionization ◽  
Copper Films ◽  
Multilayered Structures ◽  
X Ray ◽  
Electron Probe Microanalyzer ◽  
Quantitative Epma

Studies of x-ray emission from thin films on substrates using an electron probe microanalyzer (EPMA) provide useful information on the characteristics of x-ray generation by electron beams. In this study, EPMA measurements of multilayered samples were performed in order to test and improve analytical and numerical models used for quantitative EPMA. These models provide relatively accurate results for samples consisting of layers with similar average atomic numbers, because of their similar properties regarding electron transport and x-ray generation. On the contrary, these models find difficulties to describe the process when the various layers have very different atomic numbers. In a previous work, we studied the surface ionization of thin copper films of various thicknesses deposited on substrates with very different atomic numbers. In the present communication, the study is extended to the case of multilayered specimens.The studied specimens consisted of thin copper films deposited on a carbon layer which, in turn, was placed on a variety of single-element substrates, ranging from Be to Bi.

scholarly journals Determination of the Height of Hard X-Ray Sources in the Solar Atmosphere by Measurement of Photospheric Albedo Photons

1975 ◽  
Vol 68 ◽  
pp. 239-241
Author(s):  
John C. Brown ◽  
H. F. Van Beek
Keyword(s):  
Solar Atmosphere ◽  
The Other ◽  
X Ray ◽  
Theoretical Predictions ◽  
Source Models ◽  
The One

SummaryThe importance and difficulties of determining the height of hard X-ray sources in the solar atmosphere, in order to distinguish source models, have been discussed by Brown and McClymont (1974) and also in this Symposium (Brown, 1975; Datlowe, 1975). Theoretical predictions of this height, h, range between and 105 km above the photosphere for different models (Brown and McClymont, 1974; McClymont and Brown, 1974). Equally diverse values have been inferred from observations of synchronous chromospheric EUV bursts (Kane and Donnelly, 1971) on the one hand and from apparently behind-the-limb events (e.g. Datlowe, 1975) on the other.

X-Ray Diffractometry of Polymers by a Transmission Method

1964 ◽  
Vol 8 ◽  
pp. 151-161
Author(s):  
Zigmond W. Wilchinsky
Keyword(s):  
The Other ◽  
Reflection Method ◽  
Transmission Method ◽  
X Ray ◽  
Intensity Measurements ◽  
Other Hand ◽  
Line Asymmetry ◽  
Line Positions

AbstractThe practicability of using a symmetrical transmission method for accurate measurement of line positions and intensities for polymer samples was investigated. In comparison with the conventional symmetrical reflection method, the transmission method has some inherent advantages in the measurement of line positions. Very little extraneous line asymmetry is introduced by transmission, and errors due to sample misalignment can usually be corrected empirically. On the other hand, the reflection method introduces noticeable line asymmetry and a shift of the center of intensity toward smaller 2θ. Also, errors due to sample misalignment may be difficult to correct. Intensity measurements can usually be made with about the same accuracy by either method. However, the transmission method is less sensitive to misalignment errors, especially at the lower diffraction angles.

Electron Probe Microanalysis of Zinc-Bearing Hexagonal Ferrites

1965 ◽  
Vol 9 ◽  
pp. 304-313
Author(s):  
J. R. Shappirio
Keyword(s):  
Electron Probe ◽  
Hexagonal Ferrites ◽  
Structural Units ◽  
Electron Probe Analysis ◽  
X Ray ◽  
Layer Structures ◽  
Cell Data ◽  
Unit Cell Data ◽  
The Ideal

AbstractThe electron probe is shown to be an effective tool for the analysis of the series of ferrimagnetic oxides referred to as the hexagonal ferrites. This series of compounds) containing barium, Fe3+, and a divalent metal cation, is formed by an ordered stacking of basic structural units in varying ratios. The ideal, complex stoichiornewy of these polytype-like mixed-layer structures can be computed from X-ray unit cell data; the various structures and their predicted stoichiometry are reviewed. Results of electron probe analysis of zinc-bearing single-crystal hexagonal ferrites are compared with theoretical values, the various correction procedures applied to the probe data are presented, and the limitations of the method in the analysis of hexagonal ferrites are discussed. The information obtained from this study has laid the groundwork for the determination of chemistry in substituted members of the hexagonal ferrite group, and will contribute significantly to the interpretation of the magnetic properties exhibited by these compounds.

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