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1
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Synchrotron Radiation and Instrumentation at the European Synchrotron Radiation Facility

100%
Kvick Å.
Acta Physica Polonica A
|
1992
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vol. 82
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issue 1
7-12
EN
A low-emittance 6 GeV storage ring aimed at producing high-brilliance synchrotron radiation from 29 insertion devices and 27 bending magnet ports is being presently constructed in Grenoble, France. The insertion devices include undulators, wigglers and wavelength shifters giving access to high-brilliance undulator radiation as well as extremely high-flux wiggler radiation. The energy of the storage ring will produce fundamental radiation around 1 A from the undulators whereas the critical energy of the wigglers in some cases approaches 30 keV. The wavelength shifters will produce useful radiation well into the hundreds of keV region. In order to cope with the high thermal load from the insertion devices novel cooling schemes such as cryogenic cooling as well as adaptive mirror technology is being implemented. The European Synchrotron Radiation Facility will start its operation with 7 beamlines in 1994. A total of 30 facility beamlines will be built by 1999.
2
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Study of Instrumental Factors Affecting X-Ray Isochromat Spectra

63%
Pełka J. B.
Acta Physica Polonica A
|
1994
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vol. 86
|
issue 5
753-762
EN
In the present paper a model of an apparatus function for the bremsstrahlung isochromat spectroscopy method is proposed. The study presented in this work is based on experimental results obtained with a particular spectrometer working at the quantum energy of Cr K_{α1} (5414 eV). However, most of implications are general for the bremsstrahlung isochromat spectroscopy independently of particular construction of a spectrometer. From the theoretical considerations it was found that the total apparatus function, F_{t}, is composed of two main subfunctions in such a manner that F_{t} is not necessarily constant along the isochromat spectrum. The properties of the function as well as the question how it influences the measured spectra are discussed. Considerations presented in this paper are limited to the most essential instrumental factors broadening the bremsstrahlung isochromat spectra which can be described in terms of the apparatus function. In order to estimate the width of the apparatus function some experimental results of bremsstrahlung isochromat spectroscopy measurements of chosen substances with various apparatus settings are shown.
3
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Ultrabright Synchrotron Radiation Opens up New Research Frontiers

63%
Margaritondo G.
Acta Physica Polonica A
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1994
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vol. 86
|
issue 5
705-712
EN
We present an update on recent events concerning ultrabright synchrotron radiation. First and foremost, a new generation of sources has been put in operation in the past few months. Second, microscopy and spectromicroscopy - arguably the techniques that will mostly profit from ultrahigh brightness - have produced interesting results demonstrating that they are absolutely needed for a realistic picture of solid surfaces and interfaces, as well as for biological applications. Third, ultrahigh-resolution photoemission has broken new ground in the study of collective phenomena, notably the properties of the superconducting gap. Finally, we will comment on the recent use of another class of sources for practical research: infrared free electron lasers.
4
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X-Ray Absorption Spectroscopy

63%
Mobilio S.
Acta Physica Polonica A
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1994
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vol. 86
|
issue 5
645-661
EN
X-ray absorption spectroscopy, today widely used as a tool for structural investigations, is described. Theoretically it is shown that above an absorption edge the absorption coefficient is well approximated by a sum of terms, each one describing a particular path followed by the photoelectron outgoing from the atom. Such geometrical feature allows to use X-ray absorption spectroscopy for structural investigations. The data analysis procedures are outlined. Applications of the single scattering region, generally known as EXAFS to semiconductors alloys, to metallic clusters and to the crystallization of amorphous metallic glasses are illustrated. Multiple scattering calculations and their relation to experimental spectra is discussed in the case of Mn ions in solution. Application of the multiple scattering to determine the three-body correlation function in a-Si:H is shown.
5
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Distortion of the Positron Lifetime Spectra in BaF_{2} Spectrometers

63%
Goworek T., Górniak W., Wawryszczuk J.
Acta Physica Polonica A
|
1993
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vol. 83
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issue 3
307-311
EN
High efficiency of BaF_{2} scintillators creates the risk of distortion of the positron lifetime distributions due to summing and backscattering. In the 180° geometry it leads to the appearance of a spurious shortlived component.
6
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Origin of the Surface Sensitivity in Surface X-Ray Diffraction

63%
Robinson I., Eng P., Schuster R.
Acta Physica Polonica A
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1994
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vol. 86
|
issue 4
513-520
EN
The first half of this paper explains how X-ray diffraction can be sensitive to surface structure and morphology, even though X-rays interact only weakly with matter and hence penetrate deeply into the bulk medium. The basis of the crystal truncation rod construction is given, which demonstrates this sensitivity in a formal way. This is then illustrated with details of two problems of current interest which have been studied with synchrotron radiation at the National Synchrotron Light Source in New York. The structure of the Si(111)7×7 reconstructed surface, as determined in the vertical direction by X-ray reflectivity, is presented as a straightforward application of crystal truncation rods. Then we discuss alkali adsorption on Ag(110) surfaces which induces a "missing row" reconstruction. We measured the trends in the induced structural parameters as a function of Cs coverage on Ag(110), but found the greatest changes were associated with the location of the Cs instead. At high coverage this is ordered only in a one-dimensional sense, but as the coverage is reduced it becomes partially registered in the second direction, and, surprisingly, occupies a site higher above the surface.
7
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Application of Synchrotron X-Ray Topography to the Study of Materials

63%
Tanner B. K.
Acta Physica Polonica A
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1994
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vol. 86
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issue 4
537-544
EN
In this article, we review the application of synchrotron X-ray topography to the study of the defect structure of materials. Following a discussion of source and detector requirements, in situ dynamic, stroboscopic, and ultra-high strain sensitivity experiments are discussed in the context of the new, third generation, synchrotron radiation sources. The intensity and continuous spectrum of synchrotron radiation is particularly important but further use of the time structure and polarization is timely. The future potential of the technique is discussed in the context of recent results at the European Synchrotron Radiation Facility in Grenoble.
8
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X-Ray Topography Using Synchrotron Radiation

63%
Wieteska K.
Acta Physica Polonica A
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1994
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vol. 86
|
issue 4
545-552
EN
X-ray diffraction topography is a widely used method to study crystal lattice defects by visualization. The properties of synchrotron radiation relevant to topography methods extend the possibilities of investigations. These properties are the following: a high intensity, a broad spectral range, a natural collimation, a linear polarization in the horizontal plane, and a pulsed time structure. The application of synchrotron radiation to X-ray topographic studies is described and some recent examples of experiments are presented.
9
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Single-Crystal X-Ray Diffractometry Using Synchrotron Radiation

63%
Eichhorn K.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 1
51-65
EN
The properties of synchrotron radiation relevant to single-crystal X-ray diffractometry are: its high intensity over a wide spectral range, a small source size and a low divergence in the 0.1 mrad range, about 90% linear polarization in the horizontal plane, a pulsed time structure, and a time dependent intensity. The latter property requires monitoring of the primary beam intensity and its polarization state which slightly complicates data collection and needs particular attention in the data reduction stage. The other properties of synchrotron radiation, however, extend the range of X-ray diffractometry to experiments which are not feasable with sealed X-ray tubes. The high source intensity makes data collection possible on crystals down to and below 10 μm diameter. Measurement of weak and very weak ("forbidden") reflections profits from high intensity, low divergence, and a good peak-to-background ratio. Data collection at short wavelengths is useful to decrease both absorption and extinction effects and provides the resolution required for high precision structure analysis. Wavelength tun-ability is frequently used to exploit resonant X-ray scattering ("anomalous dispersion") for structure research. Examples are determination of absolute configuration, contrast variation, and phase determination from both single-and multiple-wavelength measurements ("MAD-phasing"). X-ray dichroism and double refraction are observed in the vicinity of absorption edges, causing an anisotropy and polarization dependence of anomalous scattering. This anisotropy may give rise to a violation of extinction rules for glide-planes and screw-axes, with orientation- and polarization-dependent intensities. More recently, these affects have been successfully used to derive (partial) phase information. Other applications are magnetic X-ray scattering and time-resolved X-ray diffraction, the latter exploiting the time structure of the synchrotron radiation source.
10
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Instrumentation and Methods for Powder Diffraction with Synchrotron Radiation

63%
Wroblewski T.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 1
67-81
EN
Powder diffraction covers a variety of applications ranging from high resolution structure determination to time-resolved experiments. This wide range can be covered if the properties of synchrotron radiation, especially the continuous spectrum and the high collimation, are properly taken advantage of. The latter property favours parallel beam geometry. The instrumental function for such a setup is aberration-free and can be derived using only the angular characteristics of its optical components, namely the divergence of the incoming beam and the reflection or transmission curves of the optical elements. The continuous spectrum allows either anomalous dispersion experiments or the use of a broad energy band for experiments on a short time scale. To achieve high flexibility in combination with the use of specialised setups for the different types of experiments a special diffractometer has been built at HASYLAB.
11
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Single-Crystal X-Ray Diffractometry Using Synchrotron Radiation

63%
Eichhorn K., Hümmer K.
|
EN
The outstanding properties of synchrotron radiation, in particular its high brilliancy over a wide spectral range, its low divergence, its polarization properties, and the pulsed time structure, extend the range of single-crystal X-ray diffractometry to experiments which are not feasible with conventional sources, such as sealed X-ray tubes or rotating anode equipment. Data collection techniques are strongly influenced by the general aims of a diffraction experiment, by the sample quality, its absorption and scattering power, as well as by the reflection profile shape and the instrumental resolution function. Often, the sample properties play a crucial role, and not all samples may be suitable for data collection with synchrotron X-rays. The time-dependence of the primary beam intensity and of its polarization state requires monitoring and normalization to monitor counts, which complicates data collection and data reduction due to sources of both random and systematic errors not known from conventional X-ray sources. There is almost no utilization of X-ray diffraction that cannot profit from the use of synchrotron radiation. X-ray diffraction at a synchrotron radiation source can yield structure factors of an unprecedented quality, provided proper attention is given to sample properties, to data collection strategy and data evaluation procedures. Though little is gained for strong reflections, the improvement is very pronounced for the weaker reflections, including high-order reflections, which can be measured in much shorter time than with conventional X-ray sources. However, synchrotron radiation does not provide a solution to all problems, in some cases conventional laboratory X-ray sources may be more appropriate than synchrotron radiation. Taking into account the limited access to synchrotron radiation sources, X-ray diffraction with synchrotron radiation can only supplement, but not replace conventional X-ray sources and diffraction techniques.
12
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Imaging Plates in Synchrotron and Conventional X-Ray Crystallographic Data Collection

63%
Dauter Z., Wilson K. S.
|
EN
Application of two-dimensional detectors based on imaging plates for X-ray crystallographic data collection is discussed. The properties of imaging plates are somewhat different from those of other available X-ray detectors, like film, multiwire ionization chambers, TV tubes or scintillation counters. Imaging plate scanners are well suited for laboratory X-ray sources as well as for strong synchrotron radiation. Originally developed for macromolecular crystallography, they can be used successfully to collect data on crystals of small or medium size molecules.
13
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Characterization of Concave-Curved Spectrometers for 2D X-Ray Optics

63%
Chukhovskii F. N., Chang W. Z., Förster E.
|
EN
A procedure for calculating X-ray intensity profiles analytically for various X-ray diffraction geometries has been developed, which takes into account the misalignment, the solid angle factor, the effects of convergence and/or divergence of the diffracted X-rays. The approach is applicable to X-ray optics with either a point source or a quasi-parallel beam. Moreover, using this procedure allows one to calculate the magnified image from a plasma source, the intensity profiles of topographs of bent crystals, and the spectral resolution of various focusing geometries. Several examples are presented to demonstrate the applications of this procedure. Using non-dispersive and dispersive double-crystal spectrometers, rocking curves were measured for singly and doubly bent crystals. The agreement was satisfactory with the X-ray dynamic theory of bent crystals. Furthermore, we have also extended the study of X-ray optics to include the crystal anisotropic effects. The anisotropic elasticity theory is applied to bend crystals for calculating the diffracting region on the crystal surface. The anticlastic curvature effects are analytically demonstrated with respect to the crystals' diffracting area.
14
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Biomedical Applications of Synchrotron X-Ray Fluorescence

51%
Kwiatek W. M.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 5
695-703
EN
Since the exact role of trace elements in living organisms is still not very well known, it is a need of a careful analysis and study on trace element distributions in various biomedical materials. The conventional techniques such as X-ray fluorescence, proton-induced X-ray emission, atomic absorption spectrophotometry do not always give precise determination, especially in microstructures areas. Since synchrotron radiation is very powerful and gives the opportunity to work with micro-beams the synchrotron radiation induced X-ray emission technique has been recently developed. Due to many properties of synchrotron radiation it becomes a very useful tool in science. In this paper a characterization of different apparatus for a trace element analysis as well as several applications are described to show the usefulness of the synchrotron radiation induced X-ray emission.
15
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Oscillations in Orthopositronium Annihilation in Magnetic Field in SiO_{2} Powders

51%
Berestov A. V., Talat A. S., Baranov V. V., Rudak E. A., Martsynkevich B. A.
Acta Physica Polonica A
|
1995
|
vol. 88
|
issue 1
79-82
EN
The observation method of γ-quantum angular distribution oscillations in positronium annihilation in magnetic field is essentially improved. Oscillation parameters in the experiment are in agreement with theoretical estimations.
16
Content available remote

X-Ray Standing Waves: a Powerful Tool for Interface Studies

51%
Lagomarsino S., Scarinci F., Castrucci P., Giannini C.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 4
553-566
EN
The X-ray standing wave technique has demonstrated in these last years to be a powerful method in the study of interfaces. In this paper the fundamentals of the technique will be given, together with examples of applications in the field of metal-semiconductor, of buried semiconductor-semiconductor interfaces and in structural studies of Langmuir-Blodgett films.
17
Content available remote

Examples for the Industrial Use of Synchrotron Radiation

51%
Hormes J., Chauvistré R., Schmitt W., Pantelouris M.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 1
37-50
EN
Synchrotron radiation has become a valuable tool for many fields of basic research. Several of the methods which were here developed are also suitable for solving industrial problems. Perhaps the most promising ones are the various X-ray techniques, e.g. X-ray absorption spectroscopy (EXAFS and XANES) and X-ray fluorescence. In the following article the theoretical and experimental basis for these techniques is shortly introduced and some instructive examples for such applications for actual industrial problems are dicussed. In the last section, X-ray lithography for the production of microstructures is presented as an example where synchrotron radiation is already today used for industrial production.
18
Content available remote

High Energy Resolution Photoemission Beam Line at ELETTRA

51%
Quaresima C., Ottaviani C., Matteucci M., Crotti C., Antonini A., Capozi M., Rinaldi S., Luce M., Perfetti P., Prince K. C., Astaldi C., Zacchigna M., Romanzin L., Savoia A.
|
EN
The storage ring ELETTRA in Trieste, completely dedicated to synchrotron radiation, started its operation in October 1993. We present here the high energy resolution photoemission beam line we have constructed. The beam line has been designed to perform photoemission experiments in the vacuum ultraviolet and soft X-ray. The radiation source is an undulator of type U12.5 and the photon energy range is 18-800 eV. The monochromator is a spherical grating type and the theoretical power resolution is 10^{4} in average over the entire energy range. The beam line is now installed and at the time of writing the line is being commissioned.
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