PLATINUM GROUP ELEMENT HIGH-ENERGY PIXE

K X-ray spectra have been obtained from Platinum-Group Element (PGE) minerals using 40 MeV Proton-Induced X-ray Emission. It is possible to resolve all four component X-ray lines for the PGEs. In cases where there is more than one PGE present, some K X-ray lines may overlap, but in all cases, there were single lines available for quantitative analysis. The spectrum obtained from the sperrylite during exposure to the proton beam beam contained Au X-rays. The presence of the Au can be attributed to (p,xn) reactions with Pt, induced by proton bombardment of the sample. The intensity of Au X-ray lines in the spectrum is proportional to the amount of Pt in the sample and the cross-section for (p,xn) reactions between Pt and Au at 40 MeV.

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HIGH-ENERGY PIXE: THE X-RAY SPECTRUM OF URANIUM IN AUTUNITE

International Journal of PIXE ◽

10.1142/s0129083593000112 ◽

1993 ◽

Vol 03 (02) ◽

pp. 121-127 ◽

Cited By ~ 1

Author(s):

NORMAN M. HALDEN ◽

FRANK C. HAWTHORNE

Keyword(s):

Solid State ◽

Proton Beam ◽

High Energy ◽

X Rays ◽

High Energy Proton ◽

Pixe Analysis ◽

X Ray ◽

Energy Proton ◽

Ge Detector ◽

Analytical Range

Autunite, a U-bearing mineral ( Ca(UO) 2( PO 4)2.10–12 H 2 O ), has been examined using a high-energy proton beam ( E p =40 MeV ) and Si(Li) and intrinsic Ge solid state detectors. The spectra obtained from the sample show clearly resolved U K α1, K α2 and K β X-ray lines (using the Ge detector) and Ca K α, K β X-rays, Sr K α, K β and U L X-rays (using the Si(Li) detector), this demonstrates the potential analytical range and flexibility of high energy PIXE analysis.

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Studies of metaphase chromosomes in the scanning transmission x-ray microscope: Image fidelity, radiation damage and specimen preparation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100129826 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1038-1039

Author(s):

Shawn Williams ◽

Xiaodong Zhang ◽

Susan Lamm ◽

Jack Van’t Hof

Keyword(s):

Visible Light ◽

Radiation Damage ◽

Cross Section ◽

Imaging Techniques ◽

Dose Range ◽

Specimen Preparation ◽

X Rays ◽

Metaphase Chromosomes ◽

X Ray ◽

Scanning Transmission

The Scanning Transmission X-ray Microscope (STXM) is well suited for investigating metaphase chromosome structure. The absorption cross-section of soft x-rays having energies between the carbon and oxygen K edges (284 - 531 eV) is 6 - 9.5 times greater for organic specimens than for water, which permits one to examine unstained, wet biological specimens with resolution superior to that attainable using visible light. The attenuation length of the x-rays is suitable for imaging micron thick specimens without sectioning. This large difference in cross-section yields good specimen contrast, so that fewer soft x-rays than electrons are required to image wet biological specimens at a given resolution. But most imaging techniques delivering better resolution than visible light produce radiation damage. Soft x-rays are known to be very effective in damaging biological specimens. The STXM is constructed to minimize specimen dose, but it is important to measure the actual damage induced as a function of dose in order to determine the dose range within which radiation damage does not compromise image quality.

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The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117777 ◽

1985 ◽

Vol 43 ◽

pp. 154-157

Author(s):

A.J. Tousimis

Keyword(s):

Ion Beam ◽

Depth Resolution ◽

Sample Surface ◽

High Energy ◽

X Rays ◽

X Ray ◽

Electrons And Ions ◽

Spatial Depth ◽

Minimum Surface Area ◽

Physical Principles

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

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Low-voltage EDS of magnesium ferrite Dendrites in a FEG-SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164854 ◽

1996 ◽

Vol 54 ◽

pp. 478-479

Author(s):

Matthew T. Johnson ◽

Ian M. Anderson ◽

Jim Bentley ◽

C. Barry Carter

Keyword(s):

Monte Carlo ◽

Quantitative Analysis ◽

Monte Carlo Simulations ◽

Cross Section ◽

Spatial Resolution ◽

Low Voltage ◽

Magnesium Ferrite ◽

X Ray ◽

Interaction Volume ◽

Ferrite Spinel

Energy-dispersive X-ray spectrometry (EDS) performed at low (≤ 5 kV) accelerating voltages in the SEM has the potential for providing quantitative microanalytical information with a spatial resolution of ∼100 nm. In the present work, EDS analyses were performed on magnesium ferrite spinel [(MgxFe1−x)Fe2O4] dendrites embedded in a MgO matrix, as shown in Fig. 1. spatial resolution of X-ray microanalysis at conventional accelerating voltages is insufficient for the quantitative analysis of these dendrites, which have widths of the order of a few hundred nanometers, without deconvolution of contributions from the MgO matrix. However, Monte Carlo simulations indicate that the interaction volume for MgFe2O4 is ∼150 nm at 3 kV accelerating voltage and therefore sufficient to analyze the dendrites without matrix contributions.Single-crystal {001}-oriented MgO was reacted with hematite (Fe2O3) powder for 6 h at 1450°C in air and furnace cooled. The specimen was then cleaved to expose a clean cross-section suitable for microanalysis.

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Comparison of high-angle take-off and low-angle take-off EDX detector geometry of the HF-2000 FE-TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100147107 ◽

1993 ◽

Vol 51 ◽

pp. 252-253

Author(s):

Y. Sato ◽

T. Hashimoto ◽

M. Ichihashi ◽

Y. Ueki ◽

K. Hirose ◽

...

Keyword(s):

Quantitative Analysis ◽

Field Emission ◽

Solid Angle ◽

Energy Dispersive ◽

Objective Lens ◽

X Rays ◽

High Angle ◽

X Ray ◽

Detector Geometry

Analytical TEMs have two variations in x-ray detector geometry, high and low angle take off. The high take off angle is advantageous for accuracy of quantitative analysis, because the x rays are less absorbed when they go through the sample. The low take off angle geometry enables better sensitivity because of larger detector solid angle.Hitachi HF-2000 cold field emission TEM has two versions; high angle take off and low angle take off. The former allows an energy dispersive x-ray detector above the objective lens. The latter allows the detector beside the objective lens. The x-ray take off angle is 68° for the high take off angle with the specimen held at right angles to the beam, and 22° for the low angle take off. The solid angle is 0.037 sr for the high angle take off, and 0.12 sr for the low angle take off, using a 30 mm2 detector.

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