Escape Peaks in X-Ray Diffractometry*

1964 ◽  
Vol 8 ◽  
pp. 118-133 ◽  
Author(s):  
William Parrish
Keyword(s):  
Absorption Edge ◽  
Pulse Height ◽  
Pulse Amplitude ◽  
Silicon Powder ◽  
X Rays ◽  
Pulse Height Analyzer ◽  
Escape Peak ◽  
X Ray ◽  
Absorption Edge Energy ◽  
Detector Element

AbstractEscape peaks occur when the incident X-ray quantum, energy exceeds the absorption edge energy of the detector element and the resulting X-ray fluorescence is lost from the detector. The most common escape peaks result from 1 K-fluorescence in NaI-scintillation counters and Xe K-, Xe L-, and Kr K-fluorescence in proportional counters. The average pulse amplitude of the escape peak is proportional to the difference of the Energies of the incident and fluorescent X-rays. If the intensity of the escape peak is high as in the case of Mo Kα and a kryptoopreportional counter, and the lower level of the pulse height analyzer is raised to reject the escape peak, the quantum counting efficiency may be reduced by a factor of two. When the pulse height analyzer is set for characteristic incident radiation, escape peaks appear in powder patterns at small diffraction angles. These broad low-intensity peaks are often mistakenly identified as resulting from misalignment, scattering, etc. Each powder reflection can produce its own escape peak which occurs at an angle slightly smaller than the absorption edge of the detector element. In a silicon powder pattern the three strongest reflections produce three resolved escape peaks whose peak intensities are about 4% of their corresponding Cu Kα peaks when the X-ray tube is operated at 50 kV. The escape peak intensities decrease with decreasing X-ray tube voltage and disappear when the voltage is lower than the absorption edge energy of the detector element. Absorption edge peaks observed without the upper level of the pulse height analyzer are similar in appearance, intensity, and diffraction angle to the escape peaks. In complex powder patterns the escape peak pattern is unresolved and may produce a number of very broad peaks.

SPECTRUM ANALYSIS TAKING ACCOUNT OF THE TAIL, ESCAPE FUNCTIONS AND SUB-LINES (SAPIX version 4)

2000 ◽  
Vol 10 (03n04) ◽  
pp. 101-114 ◽  
Author(s):  
K. SERA ◽  
S. FUTATSUGAWA
Keyword(s):  
Response Function ◽  
Spectrum Analysis ◽  
Peak Position ◽  
Main Peak ◽  
Small Shift ◽  
Escape Peak ◽  
X Ray ◽  
Peak Separation ◽  
Small Peak ◽  
Tail Function

A new x-ray-spectrum-analysis program, which is capable of fitting with response functions including a tail function, an escape peak and sub-lines, has been developed. In this code, the tail function is expressed by combination of two or three Gaussian functions. A tail function, an escape and sub- or satellite-lines are regarded as functions belonging to the main peak and are included in it. A small shift of peak position depending on measuring conditions can be easily corrected in the program. As a result of fitting to practical spectra with the response function thus prepared, it becomes possible to draw a smooth background over a wide x-ray-energy range and to analyze a whole spectrum simultaneously. Thus, accuracy and reproducibility of a spectrum analysis are much improved. By means of this code, correct values of peak yield of Co - K α, which overlaps with the tail of Fe - K β and is quite difficult to be accurately separated by fitting with Gaussians, have been obtained. Furthermore, accuracy of peak separation of a small peak, which overlaps with the escape peak belonging to a huge peak, has been improved. Accuracy of quantitative analysis for high-Z elements by means of Kβ yields has also been improved by using the response function including sub-lines, and it became possible to accurately separate small Kα lines from Kβ lines of the other elements.

Escape Peak, X-Ray

2016 ◽  
Author(s):  
M. De Bruin
Keyword(s):  
Escape Peak ◽  
X Ray

MEASUREMENT OF GERMANIUM ESCAPE PEAKS IN PIXE SPECTRA RECORDED USING HIGH PURITY Ge (HPGe) DETECTOR

2009 ◽  
Vol 19 (01n02) ◽  
pp. 67-76
Author(s):  
SANJIV KUMAR ◽  
G. L. N. REDDY ◽  
V. S. RAJU
Keyword(s):  
Quantitative Analysis ◽  
High Purity ◽  
Hpge Detector ◽  
X Rays ◽  
Pixe Analysis ◽  
Escape Peak ◽  
X Ray ◽  
High Purity Germanium ◽  
Experimental Values

This paper deals with studies on Ge K α and K β escape peaks in particle induced X-ray emission (PIXE) spectra recorded by a high purity germanium (HPGe) detector. A knowledge of the energies and intensities of these escape peaks is desirable for accurate qualitative as well as quantitative analysis of elements by PIXE. The spectral interferences caused by Ge K escape peaks in the determination of Fe in U by PIXE are highlighted for illustration. A simple theoretical approach based on the production of Ge K X-rays inside the Ge crystal of the detector during the process of detection of the incident characteristic X-rays and the subsequent escape of a fraction of the produced radiations from the crystal, is described to calculate the intensity ratio of the Ge escape peak to its parent characteristic X-rays. The calculated values are in agreement with the experimental values and those estimated using the formulation provided in GUPIX software for PIXE. The Ge K escape peaks are very prominent; the intensities of Ge K α escape peaks, from bromine to silver, range from 15% to 6% of those of their respective K α X-rays. These intensities are, in general, considerably higher compared to those of Si escape peaks in spectra recorded by Si ( Li ) detector. Ge K escape peaks therefore may give rise to severe interferences. The present approach provides a precise (~8%) determination of the intensity of an escape peak and thereby facilitates a reliable PIXE analysis.

Space and Time Distribution of Hard X-Ray Emission in a Loop at the Beginning of a Flare

1994 ◽  
Vol 144 ◽  
pp. 275-277
Author(s):  
M. Karlický ◽  
J. C. Hénoux
Keyword(s):  
Time Distribution ◽  
Electron Bombardment ◽  
Spatial Evolution ◽  
Superthermal Electrons ◽  
Flare Loop ◽  
X Ray ◽  
Superthermal Electron ◽  
Flare Loops ◽  
Chromospheric Evaporation ◽  
Temporal And Spatial

AbstractUsing a new ID hybrid model of the electron bombardment in flare loops, we study not only the evolution of densities, plasma velocities and temperatures in the loop, but also the temporal and spatial evolution of hard X-ray emission. In the present paper a continuous bombardment by electrons isotropically accelerated at the top of flare loop with a power-law injection distribution function is considered. The computations include the effects of the return-current that reduces significantly the depth of the chromospheric layer which is evaporated. The present modelling is made with superthermal electron parameters corresponding to the classical resistivity regime for an input energy flux of superthermal electrons of 109erg cm−2s−1. It was found that due to the electron bombardment the two chromospheric evaporation waves are generated at both feet of the loop and they propagate up to the top, where they collide and cause temporary density and hard X-ray enhancements.

Some Problems in Understanding the Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 1-9
Author(s):  
A. H. Gabriel
Keyword(s):  
Solar Corona ◽  
Solar Atmosphere ◽  
Theoretical Modelling ◽  
Total System ◽  
Major Advance ◽  
X Ray ◽  
Proper Perspective ◽  
Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

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