Mosaic crystal X-ray spectrometer to resolve inelastic background from anomalous scattering experiments

Ice, Gene E.; Sparks, C. J.

doi:10.1016/0168-9002(90)90043-6

Cited by 82 publications

(55 citation statements)

References 17 publications

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“…As the source size increases, the energy resolution decreases and increasingly small incident beams are required for good energy resolution (Ice and Sparks, 1990). In addition, the effective source size as viewed by the crystal spectrometer depends on the spread of the incident beam on the sample and the angle of the detector axis to the sample surface.…”

Section: Removal Of Inelastic Scattering Backgroundsmentioning

confidence: 99%

X‐ray and Neutron Diffuse Scattering Measurements

Ice

Robertson

Sparks

2012

Characterization of Materials

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Diffuse scattering from crystalline solid solutions is used to measure local compositional order among the atoms, dynamic displacements (phonons), and mean species‐dependent static displacements. It can also provide information on defects including vacancies, interstitials, dislocations and truncated sample dimensions. In locally ordered alloys, fluctuations of composition and interatomic distances break the long‐range symmetry of the crystal within local regions and contribute to the total energy of the alloy. Local ordering can be a precursor to a lower temperature equilibrium structure that may be unattainable because of slow atomic diffusion. In addition to local atomic correlations, neutron diffuse scattering methods can be used to study the local short‐range correlations of the magnetic moments. Interstitial defects, as opposed to the substitutional disorder defects described above, also disrupt the long‐range periodicity of a crystalline material and give rise to diffusely scattered x‐rays, neutrons, and electrons. This article will concentrate on the use of diffuse x‐ray and neutron scattering from single crystals to measure local chemical correlations and chemically specific static displacements. Particular emphasis is placed on the use of resonant (anomalous) x‐ray techniques to extract information on atomic size from binary solid solutions with short‐range order. By separating this diffuse intensity into its component parts we are able to recover pair correlation probabilities for the three kinds of pairs in a binary alloy. The interpretation of diffuse scattering associated with dynamic displacements of atoms from their average crystal sites are discussed briefly in this article.

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Section: Removal Of Inelastic Scattering Backgroundsmentioning

confidence: 99%

X‐ray and Neutron Diffuse Scattering Measurements

Ice

Robertson

Sparks

2012

Characterization of Materials

View full text Add to dashboard Cite

Diffuse scattering from crystalline solid solutions is used to measure local compositional order among the atoms, dynamic displacements (phonons), and mean species‐dependent static displacements. It can also provide information on defects including vacancies, interstitials, dislocations and truncated sample dimensions. In locally ordered alloys, fluctuations of composition and interatomic distances break the long‐range symmetry of the crystal within local regions and contribute to the total energy of the alloy. Local ordering can be a precursor to a lower temperature equilibrium structure that may be unattainable because of slow atomic diffusion. In addition to local atomic correlations, neutron diffuse scattering methods can be used to study the local short‐range correlations of the magnetic moments. Interstitial defects, as opposed to the substitutional disorder defects described above, also disrupt the long‐range periodicity of a crystalline material and give rise to diffusely scattered x‐rays, neutrons, and electrons. This article will concentrate on the use of diffuse x‐ray and neutron scattering from single crystals to measure local chemical correlations and chemically specific static displacements. Particular emphasis is placed on the use of resonant (anomalous) x‐ray techniques to extract information on atomic size from binary solid solutions with short‐range order. By separating this diffuse intensity into its component parts we are able to recover pair correlation probabilities for the three kinds of pairs in a binary alloy. The interpretation of diffuse scattering associated with dynamic displacements of atoms from their average crystal sites are discussed briefly in this article.

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“…1 shows the so-called mosaic focusing, the reason for the 20 to 50 times higher integral reectivity of mosaic crystals. For further details, we refer the reader to the excellent publication of Ice and Sparks, 8 who describe the properties of HOPG based von Hamos spectrometers in detail.…”

Section: The Hapg Von Hamos Spectrometermentioning

confidence: 99%

XAFS spectroscopy by an X-ray tube based spectrometer using a novel type of HOPG mosaic crystal and optimized image processing

Schlesiger

Anklamm

Stiel

et al. 2015

J. Anal. At. Spectrom.

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a This paper presents recent achievements in laboratory based instrumentation for X-ray Absorption Fine Structure Spectroscopy (XAFS). The key component of the spectrometer is a HAPG mosaic crystal, which is employed in the von Hamos geometry. Due to the high efficiency of HAPG a low power micro focus X-ray tube can serve as an X-ray source. Besides a description of the spectrometer, the paper covers the treatment of the CCD images in detail. The latter is crucial in order to entirely exploit the potential of the HAPG (Highly Annealed Pyrolitic Graphite) spectrometer. One section is dedicated to applications. As a first kind of application, the concentrations of two different iron species in mixtures are determined. A second kind of typical usage of XAFS is the determination of bond lengths from the EXAFS. This XAFS application is demonstrated with metallic Ni as a reference material.

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“…This inefficiency is unacceptable for typical weak diffuse x-ray scattering. A mosaic crystal x-ray spectrometer (Ice and Sparks, 1990) has been found to be a more practical device. The advantages of a mosaic crystal spectrometer is that it is possible to obtain energy resolutions similar to that of a perfect crystal spectrometer, but with an overall angular acceptance and efficiency similar to those of a solid-state detector.…”

Section: Removal Of Inelastic Scattering Backgroundsmentioning

confidence: 99%

X‐Ray and Neutron Diffuse Scattering Measurements

Ice¹,

Robertson²,

Sparks³

2002

Characterization of Materials

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Diffuse scattering from crystalline solid solutions is used to measure local compositional order among the atoms, dynamic displacements (phonons), and mean species‐dependent static displacements. In locally ordered alloys, fluctuations of composition and interatomic distances break the long‐range symmetry of the crystal within local regions and contribute to the total energy of the alloy. Local ordering can be a precursor to a lower temperature equilibrium structure that may be unattainable because of slow atomic diffusion. In addition to local atomic correlations, neutron diffuse scattering methods can be used to study the local short‐range correlations of the magnetic moments. Interstitial defects, as opposed to the substitutional disorder defects described above, also disrupt the long‐range periodicity of a crystalline material and give rise to diffusely scattered x rays, neutrons, and electrons. This article will concentrate on the use of diffuse x‐ray and neutron scattering from single crystals to measure local chemical correlations and chemically specific static displacements. Particular emphasis is placed on the use of resonant (anomalous) x‐ray techniques to extract information on atomic size from binary solid solutions with short‐range order. Here the alloys have a well‐defined average lattice but have local fluctuations in composition and displacements from the average lattice. In stoichiometric crystals with long‐range periodicity, sharp superlattice Bragg reflections appear. If the compositional order is correlated only over short distances, the superlattice reflections are so broadened that measurements throughout a symmetry related volume in reciprocal space are required to determine its distribution. In addition, the displacement of the atom pairs (e.g., the A‐A, A‐B, and B‐B pairs in a binary alloy) from the sites of the average lattice because of different atom sizes also contributes to the distribution of this diffuse scattering. By separating this diffuse intensity into its component parts—that associated with the chemical preference for A‐A, A‐B, and B‐B pairs for the various near‐neighbor shells and that associated with the static and dynamic displacements of the atoms from the sites of the average lattice—we are able to recover pair correlation probabilities for the three kinds of pairs in a binary alloy. The interpretation of diffuse scattering associated with dynamic displacements of atoms from their average crystal sites are discussed only briefly in this article.

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Mosaic crystal X-ray spectrometer to resolve inelastic background from anomalous scattering experiments

Cited by 82 publications

References 17 publications

X‐ray and Neutron Diffuse Scattering Measurements

X‐ray and Neutron Diffuse Scattering Measurements

XAFS spectroscopy by an X-ray tube based spectrometer using a novel type of HOPG mosaic crystal and optimized image processing

X‐Ray and Neutron Diffuse Scattering Measurements

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