AEM: From microns to atoms

1992 ◽  
Vol 50 (2) ◽  
pp. 1464-1465
Author(s):  
Graham Cliff ◽  
Gordon W. Lorimer
Keyword(s):  
Electron Beam ◽  
Analytical Electron Microscopy ◽  
High Energy ◽  
Simple Relationship ◽  
X Ray ◽  
Physics Department ◽  
The University ◽  
University Of Manchester ◽  
A Current ◽  
Made In

The “Manchester Connection” with analytical electron microscopy (AEM) goes back to 1913 and the work of Moseley which was carried out in the Physics Department of the University of Manchester. It was Moseley who first pointed out that there is a simple relationship between Z, the atomic number of an element, and Ek,the energy of the characteristic K-shell X-ray. This relationship is enshrined in Moseley's Law, Ek = 10.3(Z-1).The origin of the modern bulk microprobe analyzer lies in the Ph.D. project of Castaing. Under the supervision of Guinier, Castaing combined an electron microscope and an X-ray spectrometer and obtained a current of a few nA in an electron beam under a micron in diameter. Although enormous advances were made in instrumentation and quantification in the 1950's and 1960's, the spatial resolution for microprobe analysis remained at about 1 μm3 or a mass of about 10-12g, no matter how small the diameter of the incident electron beam. This limitation arises from the physics of the interaction of a high energy electron beam with a solid sample.

Searching for the causes why some of the paintings by Mihaly Munkacsy are darkening

1990 ◽  
Vol 48 (2) ◽  
pp. 204-205
Author(s):  
Imre Pozsgai ◽  
Klara Erdöhalmi-Torok
Keyword(s):  
Electron Beam ◽  
Cross Section ◽  
Polyester Resin ◽  
National Gallery ◽  
X Ray ◽  
Art Historians ◽  
Made In ◽  
Grinding And Polishing

The paintings by the great Hungarian master Mihaly Munkacsy (1844-1900) made in an 8-9 years period of his activity are deteriorating. The most conspicuous sign of the deterioration is an intensive darkening. We have made an attempt by electron beam microanalysis to clarify the causes of the darkening. The importance of a study like this is increased by the fact that a similar darkening can be observed on the paintings by Munkacsy’s contemporaries e.g Courbet and Makart. A thick brown mass the so called bitumen used by Munkacsy for grounding and also as a paint is believed by the art historians to cause the darkening.For this study, paint specimens were taken from the following paintings: “Studio”, “Farewell” and the “Portrait of the Master’s Wife”, all of them are the property of the Hungarian National Gallery. The paint samples were embedded in a polyester resin “Poly-Pol PS-230” and after grinding and polishing their cross section was used for x-ray mapping.

Contribution of Cerenkov radiation in high-energy x-ray and electron beam film dosimetry using water-substitute phantoms

2003 ◽  
Vol 48 (6) ◽  
pp. N105-N109 ◽  
Author(s):  
Tatsuya Fujisaki ◽  
Hidetoshi Saitoh ◽  
Takeshi Hiraoka ◽  
Akio Kuwabara ◽  
Shinji Abe ◽  
...  
Keyword(s):  
Electron Beam ◽  
High Energy ◽  
Cerenkov Radiation ◽  
Film Dosimetry ◽  
X Ray

Optimizing Spatial Resolution for X-ray Microanalysis

2001 ◽  
Vol 7 (S2) ◽  
pp. 694-695
Author(s):  
Eric Lifshin ◽  
Raynald Gauvin ◽  
Di Wu
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Spatial Resolution ◽  
Maximum Diameter ◽  
Thin Sections ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Limiting Value ◽  
Made In

In Castaing’s classic Ph.D. dissertation he described how the limiting value of x-ray spatial resolution for x-ray microanalysis, of about 1 μm, was not imposed by the diameter of the electron beam, but by the size of the region excited inside the specimen. Fifty years later this limit still applies to the majority of measurement made in EMAs and SEMs, even though there is often a need to analyze much finer structures. When high resolution chemical analysis is required, it is generally necessary to prepare thin sections and examine them in an analytical electron microscope where the maximum diameter of the excited volume may be as small as a few nanometers. Since it is not always possible or practical, it is important to determine just what is the best spatial resolution attainable for the examination of polished or “as received” samples with an EMA or SEM and how to achieve it experimentally.

scholarly journals Harry Lambert Welsh, 23 March 1910 - 23 July 1984

1994 ◽  
Vol 39 ◽  
pp. 433-450
Keyword(s):  
High Energy Physics ◽  
Molecular Spectroscopy ◽  
Intermolecular Forces ◽  
High Energy ◽  
Alma Mater ◽  
Research Groups ◽  
University Of Toronto ◽  
Physics Department ◽  
The University ◽  
Energy Physics

Harry Lambert Welsh began a long association with the University of Toronto with his enrolment in undergraduate physics in 1926. He brought fame to his Alma Mater with pioneering studies in molecular spectroscopy and intermolecular forces, and he played a major role in the development of the Physics Department with his introduction and establishment of research groups in theoretical, atmospheric, and high-energy physics. Undoubtedly, Harry Welsh’s greatest achievement was the stimulation for scholarly research engendered in 65 Ph.D. students who had the privilege and pleasure to study under his supervision over a period of four decades. These scientists have made, and are continuing to make, important contributions to research in a variety of ways in universities, industry, and government institutions, across Canada and in other countries.

Surface Structure of Sulfur Coated GaAs

1989 ◽  
Vol 163 ◽  
Author(s):  
Yoshihisa Fujisaki ◽  
Shigeo Goto
Keyword(s):  
Electron Beam ◽  
Surface Structure ◽  
Chemical Bond ◽  
Photoelectron Spectroscopy ◽  
Strong Dependence ◽  
High Energy ◽  
Chemical Bonds ◽  
High Energy Electron ◽  
X Ray ◽  
Beam Diffraction

AbstractSurface structure of (NH4)2S treated GaAs. is investigated using PL (PhotoLuminescence), XPS (X-ray Photoelectron Spectroscopy) and RHEED (Reflection of High Energy Electron beam Diffraction). The data taken with these techniques show the strong dependence upon the crystal orientations coming from the stabilities of chemical bonds of Ga-S and As-S on GaAs crystals. The greater enhancement of PL intensity, the clearer RHEED patterns and the smaller amount of oxides on (111)A than (111)B implies the realization of a more stable structure composed mainly of the Ga-S chemical bond.

Sky survey of high-energy cosmic X-rays and spectral information on sources in the Crab nebula, Cygnus, and Scorpius

1968 ◽  
Vol 46 (10) ◽  
pp. S409-S413 ◽  
Author(s):  
Walter H. G. Lewin ◽  
George W. Clark ◽  
William B. Smith
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
X Rays ◽  
Coma Cluster ◽  
X Ray ◽  
Sky Survey ◽  
Upper Limits ◽  
Intensity Ratios ◽  
The Crab Nebula ◽  
Made In

A complete X-ray survey of the northern sky has been made in the energy range 20–100 keV. Spectra are given for Cyg X-1 and Tau X-1. Intensity ratios (Cyg X-1/Tau X-1) of 0.84 ± 0.10 and 1.30 ± 0.25 were derived in the 20–70 keV range from data obtained on July 19, 1966 and February 13, 1967, respectively. Observations on Sco X-1 and the Coma cluster show upper limits which are quite different from results reported by other groups.

X-ray spectroscopy and spectropolarimetry of high energy density plasma complemented by LLNL electron beam ion trap experiments

2003 ◽  
Vol 74 (3) ◽  
pp. 1947-1950 ◽  
Author(s):  
A. S. Shlyaptseva ◽  
D. A. Fedin ◽  
S. M. Hamasha ◽  
S. B. Hansen ◽  
C. Harris ◽  
...  
Keyword(s):  
Electron Beam ◽  
Energy Density ◽  
Ion Trap ◽  
High Energy ◽  
High Energy Density ◽  
X Ray ◽  
Electron Beam Ion Trap ◽  
Density Plasma

scholarly journals Prospects for Coordinated Observations with XTE

1995 ◽  
Vol 12 (2) ◽  
pp. 219-226 ◽  
Author(s):  
A. B. Giles ◽  
K. Jahoda ◽  
J. H. Swank ◽  
W. Zhang
Keyword(s):  
High Energy ◽  
High Time Resolution ◽  
Massachusetts Institute Of Technology ◽  
Large Area ◽  
X Ray ◽  
Transient Sources ◽  
Sky Monitor ◽  
Institute Of Technology ◽  
Proportional Counter Array ◽  
The University

AbstractThe X-ray Timing Explorer (XTE) is a NASA satellite designed to perform high-time-resolution studies of known X-ray sources. The two main experiments are a large-area proportional counter array (PCA) from the Goddard Space Flight Center (GSFC) and a high-energy X-ray timing experiment (HEXTE) from the University of California at San Diego (UCSD). The PCA data is processed by an electronic data system (EDS) built by the Massachusetts Institute of Technology (MIT) that performs many parallel processing analysis functions for on-board evaluation and data compression. MIT also provide an all-sky monitor (ASM) experiment so that XTE can be slewed rapidly to new transient sources. The spacecraft provides a mean science telemetry rate for the PCA of ~20 kilobits per second (kbps), with bursts to 256 kbps for durations of 30 minutes. Photons are tagged to 1 μs and absolute timing should be better than 100 μs. XTE is due for launch in late August 1995 and the first NASA Research Announcement (NRA) is due out in January 1995. This paper summarises XTE’s performance and then discusses the interactive and flexible operations of the satellite and some of the science it can do. These features should make XTE a productive spacecraft for coordinated observation programs.

scholarly journals The importance of EBIT data for Z-pinch plasma diagnostics

2008 ◽  
Vol 86 (1) ◽  
pp. 267-276 ◽  
Author(s):  
A S Safronova ◽  
V L Kantsyrev ◽  
P Neill ◽  
U I Safronova ◽  
D A Fedin ◽  
...  
Keyword(s):  
Electron Beam ◽  
Lawrence Livermore National Laboratory ◽  
National Laboratory ◽  
Theoretical Models ◽  
High Energy ◽  
High Energy Density ◽  
Strong Electron ◽  
Model Calculations ◽  
X Ray ◽  
Z Pinch

The results from the last six years of X-ray spectroscopy and spectropolarimetry of high-energy density Z-pinch plasmas complemented by experiments with the electron beam ion trap (EBIT) at the Lawrence Livermore National Laboratory (LLNL) are presented. The two topics discussed are the development of M-shell X-ray W spectroscopic diagnostics and K-shell Ti spectropolarimetry of Z-pinch plasmas. The main focus is on radiation from a specific load configuration called an “X-pinch”. In this work the study of X-pinches with tungsten wires combined with wires from other, lower Z materials is reported. Utilizing data produced with the LLNL EBIT at different energies of the electron beam the theoretical prediction of line positions and intensity of M-shell W spectra were tested and calibrated. Polarization-sensitive X-pinch experiments at the University of Nevada, Reno (UNR) provide experimental evidence for the existence of strong electron beams in Ti and Mo X-pinch plasmas and motivate the development of X-ray spectropolarimetry of Z-pinch plasmas. This diagnostic is based on the measurement of spectra recorded simultaneously by two spectrometers with different sensitivity to the linear polarization of the observed lines and compared with theoretical models of polarization-dependent spectra. Polarization-dependent K-shell spectra from Ti X-pinches are presented and compared with model calculations and with spectra generated by a quasi-Maxwellian electron beam at the LLNL EBIT-II electron beam ion trap.PACS Nos.: 32.30.Rj, 52.58.Lq, 52.70.La

Quantification of losses during X-ray microanalysis of mercury

1978 ◽  
Vol 36 (2) ◽  
pp. 12-13
Author(s):  
T. Bistricki
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Mass Loss ◽  
Atomic Number ◽  
High Vacuum ◽  
Analytical Electron Microscopy ◽  
X Ray ◽  
Low Level ◽  
Analytical Electron ◽  
Concentration Levels

Diminution of the X-ray signal from the elements of low atomic number and mass loss associated with electron excited X-ray microanalysis have been demonstrated elsewhere. The elements of higher atomic number did not receive sufficient attention although under severe conditions of analytical electron microscopy, the losses of any of the specimen's elemental components exposed to the electron beam bombardment in high vacuum are to be expected and have been indicated previously. Unlike the elements of low atomic number, the losses of heavier elements, like mercury, are usually not detected unless a mass of the element within the excited volume is at a very low level (10-11 g range or less) or analytical conditions are extremely unfavourable, in which case considerable losses may occur even when concentration levels are by orders of magnitude higher (10-9 g range or higher).

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