Multilayer Scatterers for Use in Polarized X-Ray Flourescence

In the EDXRF analysis of minor and trace elements in a variety of matrices, the use of a polarized x-ray source incident on a sample will provide minimum detection limits three to five times lower than the use of non-polarized sources (1,2). There are various methods of producing monochromatic polarized x-rays for specimen excitation (3,4,5,6 ). Such x-ray sources may produce the lowest detection limits for a single element or a narrow range of elements. However, if one is interested in simultaneously analyzing a broad range of elements, a polychromatic source is desired (7,8,9). We present here a new method for producing broad-band polarized x-rays.

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X-Ray Polarization: Bragg Diffraction and X-Ray Flurorescence

Advances in X-ray Analysis ◽

10.1154/s0376030800012659 ◽

1982 ◽

Vol 26 ◽

pp. 331-336

Author(s):

John D. Zahrt

Keyword(s):

State Of The Art ◽

Detection Limits ◽

Bragg Diffraction ◽

X Rays ◽

X Ray ◽

Signal Noise ◽

Noise Ratio ◽

Minimum Detection Limits

Recent, state of the art, x-ray spectrometers have made use of polarizing the source x-rays by scattering through 90° (1) . One then observes the analyte fluorescence in a direction perpendicular to the scattering plane in which the polarized x-rays are generated. The signal/noise ratio at the detector is much improved. Unfortunately there is a concomitant loss of intensity and analysis times increase. This adversely affects the minimum detection limits.

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Intensity and Distribution of Background X-Rays in a Wavelength-Dispersive Spectrometer. II. Applications

Advances in X-ray Analysis ◽

10.1154/s0376030800020334 ◽

1988 ◽

Vol 32 ◽

pp. 83-87

Author(s):

K. Omote ◽

T. Arai

Keyword(s):

Trace Elements ◽

Spectroscopic Analysis ◽

Background Intensity ◽

X Rays ◽

Correction Procedure ◽

Minor And Trace Elements ◽

X Ray ◽

Powder Samples ◽

Analytical Accuracy ◽

Wavelength Dispersive Spectrometer

In the spectroscopic analysis of minor and trace elements by fluorescent X-rays, many improvements in the analytical performance of trace element measurements have been made. For the analysis of trace elements, the background intensity governs the analytical accuracy and the lowest detection limit in a sample. A comparison is made between experimental and theoretically calculated background X-ray intensities in a previous paper. It is based on the formula for scattered X-ray intensity, from the estimation of Thomson and Compton scattered X-rays. Also, the asymmetrical peak profiles at the base of the giant intensity peak are discussed and are clearly shown in the skirt part of K beta X-rays, e.g. , Ni-K beta or Fe-K beta X-rays. The purpose of this report is to investigate the intensity of background X-rays, using glass beads and powder samples of iron oxide and quartz, based on the previous fundamental studies and the overlapping correction procedure for cobalt determination in low-alloy and stainless steel.

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Digital x-ray mapping of nanometer-size supported bimetallic catalysts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104716 ◽

1988 ◽

Vol 46 ◽

pp. 530-531

Author(s):

L. T. Germinario

Keyword(s):

Background Radiation ◽

Metal Cluster ◽

Single Element ◽

Beam Diameter ◽

X Rays ◽

X Ray ◽

Major Interest ◽

Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

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XRMF applications of a monolithic, polycapillary, focusing x-ray optic

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100163666 ◽

1996 ◽

Vol 54 ◽

pp. 240-241

Author(s):

D. A. Carpenter ◽

Ning Gao ◽

G. J. Havrilla

Keyword(s):

Trace Elements ◽

Point Source ◽

Focal Spot ◽

Fluorescence Analysis ◽

X Rays ◽

Focal Distance ◽

Spot Diameter ◽

X Ray ◽

Focal Spot Diameter

A monolithic, polycapillary, x-ray optic was adapted to a laboratory-based x-ray microprobe to evaluate the potential of the optic for x-ray micro fluorescence analysis. The polycapillary was capable of collecting x-rays over a 6 degree angle from a point source and focusing them to a spot approximately 40 µm diameter. The high intensities expected from this capillary should be useful for determining and mapping minor to trace elements in materials. Fig. 1 shows a sketch of the capillary with important dimensions.The microprobe had previously been used with straight and with tapered monocapillaries. Alignment of the monocapillaries with the focal spot was accomplished by electromagnetically scanning the focal spot over the beveled anode. With the polycapillary it was also necessary to manually adjust the distance between the focal spot and the polycapillary.The focal distance and focal spot diameter of the polycapillary were determined from a series of edge scans.

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Review of GRANAT Observations of AGNs

Symposium - International Astronomical Union ◽

10.1017/s0074180900174856 ◽

1994 ◽

Vol 159 ◽

pp. 63-72 ◽

Cited By ~ 2

Author(s):

E. Churazov ◽

M. Gilfanov ◽

A. Finoguenov ◽

R. Sunyaev ◽

M. Chernyakova ◽

...

Keyword(s):

Time Scales ◽

Gamma Ray ◽

Broad Band ◽

Band 3 ◽

X Rays ◽

X Ray ◽

X Ray Background

Brief review of AGNs observations in the X-ray / soft gamma-ray bands with the orbital observatory GRANAT is presented.For three well known bright objects (3C273, NGC4151 and Cen A) broad band (3 keV–few hundreds keV) spectra have been obtained. Imaging capabilities allowed accurate (several arcminutes) identification of these objects with sources of hard X-rays.The spectrum of NGC4151 above ≈ 50 keV was found to be much steeper than that in most of the previous observations, while in standard X-ray band the spectrum agrees with observed previously. The comparison of the observed spectra with that of the X-Ray Background (XRB) indicates that sources similar to NGC4151 could reproduce the shape of XRB spectrum in 3–60 keV band.Cen A was observed in the very low state during most of observations in 1990–1993, except for two observations in 1991. The variability of the hard X-ray flux has been detected on the time scales of several days.

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New insight into the origin of the GeV flare in the binary system PSR B1259-63/LS 2883 from the 2017 periastron passage

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1876 ◽

2020 ◽

Vol 497 (1) ◽

pp. 648-655

Author(s):

M Chernyakova ◽

D Malyshev ◽

S Mc Keague ◽

B van Soelen ◽

J P Marais ◽

...

Keyword(s):

Binary System ◽

Light Curve ◽

Energy Release ◽

Broad Band ◽

Strong Shock ◽

Optical Observations ◽

X Rays ◽

X Ray ◽

Inverse Compton ◽

Pulsar Wind

ABSTRACT PSR B1259-63 is a gamma-ray binary system hosting a radio pulsar orbiting around an O9.5Ve star, LS 2883, with a period of ∼3.4 yr. The interaction of the pulsar wind with the LS 2883 outflow leads to unpulsed broad-band emission in the radio, X-rays, GeV, and TeV domains. While the radio, X-ray, and TeV light curves show rather similar behaviour, the GeV light curve appears very different with a huge outburst about a month after a periastron. The energy release during this outburst seems to significantly exceed the spin-down luminosity of the pulsar and both the GeV light curve and the energy release vary from one orbit to the next. In this paper, we present for the first time the results of optical observations of the system in 2017, and also reanalyse the available X-ray and GeV data. We present a new model in which the GeV data are explained as a combination of the bremsstrahlung and inverse Compton emission from the unshocked and weakly shocked electrons of the pulsar wind. The X-ray and TeV emission is produced by synchrotron and inverse Compton emission of energetic electrons accelerated on a strong shock arising due to stellar/pulsar winds collision. The brightness of the GeV flare is explained in our model as a beaming effect of the energy released in a cone oriented, during the time of the flare, in the direction of the observer.

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Rapid Quantitative Analysis by X-Ray Spectrometry

Advances in X-ray Analysis ◽

10.1154/s0376030800010880 ◽

1971 ◽

Vol 15 ◽

pp. 164-175 ◽

Cited By ~ 6

Author(s):

Robert D. Giauque ◽

Joseph M. Jaklevic

Keyword(s):

Cross Sections ◽

Fluorescence Analysis ◽

Selective Excitation ◽

Single Element ◽

X Rays ◽

Analysis Method ◽

Yield Data ◽

X Ray ◽

Minimum Number ◽

Sample Dilution

An x-ray fluorescence analysis method applicable to the case of fluorescent spectra excited with monoenergetic x-rays has been developed. The technique employs a minimum number of calibration steps using single element thin film standards and depends upon theoretical cross sections and fluorescent yield data to interpolate from element to element. The samples are treated as thin films and corrections for absorption effects are easily determined- Enhancement effects, if not negligible, are minimized by sample dilution techniques or by selective excitation.

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Sample Preparation Optimization for EDXRF Analysis of Portland Cement

Advances in X-ray Analysis ◽

10.1154/s0376030800020504 ◽

1988 ◽

Vol 32 ◽

pp. 221-226

Author(s):

Wayne Watson ◽

Jim Parker ◽

Anthony R. Harding

Keyword(s):

Sample Preparation ◽

Portland Cement ◽

Preparation Methods ◽

X Ray ◽

Accuracy And Precision ◽

Edxrf Analysis ◽

Analytical Accuracy ◽

Minimum Detection Limits ◽

Sample Preparation Methods

AbstractVarious sample preparation methods for Energy Dispersive X-ray Fluorescence (EDXRF) analysis of Portland cement were compared in order to evaluate improvement in analytical accuracy and precision. Sample preparation requirements for EDXRF are slightly different than for Wavelength Dispersive X-ray Fluorescence (WDXRF), and the methods commonly used in WDXRF are not optimized for EDXRF. Primarily, the work focuses on techniques for producing a fused sample with the lowest practical concentration of lithium borate flux. Determination of minimum detection limits were made from samples with varying proportions of flux in order to evaluate analytical optimization. Ease and reproducibility of preparation of the sample was also considered.

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