Direct observation of mosaic blocks in highly oriented pyrolytic graphite

Ohler, M.; Baruchel, J.; Moore, Arthur; Galez, Ph.; Freund, Andreas K.

doi:10.1016/s0168-583x(97)00204-8

Cited by 31 publications

(19 citation statements)

References 3 publications

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“…The image presents spatial non-uniformities, that are due to structural characteristics of pyrolytic graphite. [24][25][26] This characteristic of the dichromatic beam has already been studied in another paper, 27 where the results of a detailed topographic study of mean energy and flux has been reported. We estimated that the observed gradients don't affect the results of dual-energy technique application in a appreciable way, if the proper correction procedures are used.…”

Section: X-ray Beam Investigationmentioning

confidence: 81%

<title>Dichromatic source for the application of dual-energy tissue cancellation in mammography</title>

et al. 2002

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A novel x-ray source, providing dichromatic beams for the application of dual-energy radiography, has been assembled and studied. The system works via Bragg diffraction, by monochromatizing the beam produced by a conventional W-anode x-ray tube with a mosaic crystal monochromator. The source generates a laminar beam (10 cm-high and 0.8 cm-wide), composed by two spatially superimposed quasi-monochromatic beams. The characteristics of the radiation field in terms of energy resolution and fluence have been reported, for three pairs of energies. A study of the spectra attenuated by several phantoms of breast equivalent tissue of different thicknesses shows that the optimal energy of the dichromatic beam for dual energy mammography application ranges between 18/36 keV and 18.6/37.2 keV and may be set as a function of the thickness or density of investigated tissue.

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Section: X-ray Beam Investigationmentioning

confidence: 81%

<title>Dichromatic source for the application of dual-energy tissue cancellation in mammography</title>

et al. 2002

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“…The same sample was earlier characterized with projection X-ray topography by Ohler et al (1997). In the present investigation, this sample was chosen because it contains large crystalline domains which can be clearly resolved on an X-ray topograph.…”

Section: Samples Experimental Methods and Equipmentmentioning

confidence: 99%

“…However, an arrangement of crystallites to form crystalline domains of similar orientation has been concluded from several experiments. These domains have been visualized by Ohler et al (1997) employed using X-ray diffraction techniques. Ohler et al (1997) employed a narrow and highly collimated beam of monochromatic X-rays to enhance the quality of section topographs.…”

Section: Introductionmentioning

confidence: 99%

“…These domains have been visualized by Ohler et al (1997) employed using X-ray diffraction techniques. Ohler et al (1997) employed a narrow and highly collimated beam of monochromatic X-rays to enhance the quality of section topographs. Later, a similar technique was employed to characterize several HOPG samples for X-ray optical applications (Tuffanelli et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

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X-ray topographic determination of the granular structure in a graphite mosaic crystal: a three-dimensional reconstruction

Ohler¹,

Rı́o²,

Tuffanelli³

et al. 2000

J Appl Crystallogr

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Section topographs recorded at different spatial locations and at different rocking angles of a highly oriented pyrolytic graphite (HOPG) crystal allow three-dimensional maps of the local angular-dependent scattering power to be obtained. This is performed with a direct reconstruction from the intensity distribution on such topographs. The maps allow the extraction of information on local structural parameters such as size, form and internal mosaic spread of crystalline domains. This data analysis leads to a new method for the characterization of mosaic crystals. Perspectives and limits of applicability of this method are discussed

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“…Now-a-days PG is commonly used as high efficient neutron monochromator and filter since it has low absorption cross section and high scattering one (Adib et al, 2011;Adib et al, 2006a;Adib et al, 2006b;Mildner et al, 2001;Mook et al, 2001). Moreover now a bulk PG crystal with small mosaic spread at reasonable price is available (Ohler et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Pyrolytic Graphite as a Neutron Monochromator

Adib¹,

Habib²,

El-Mesiry³

et al. 2012

EER

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Pyrolytic graphite (PG) has become nearly indispensable in neutron spectroscopy. Since the integrated reflectivity of the monochromatic neutrons from PG crystals cut along its c-axis is high within a wavelength band from 0.1 nm up to 0.65 nm. The monochromatic features of PG crystal is detailed in terms of the optimum mosaic spread, crystal thickness and reactor moderating temperature for efficient integrated neutron reflectivity within the wavelength band. A computer code Mono-PG has been developed to carry out the required calculations for the PG hexagonal close-packed structure.Calculation shows that, 2 mm thick of PG crystal having 0.3 0 FWHM on mosaic spread are the optimum parameters of PG crystal as a monochromator at selected neutron wavelength shorter than 0.2 nm. However, the integrated neutron intensity of 2 nd and 3 rd orders from a thermal reactor flux is even higher than that of the 1 st order one at neutron wavelengths longer than 0.2 nm. While, from a cold reactor flux, the integrated neutron intensity of the 1 st order within the wavelength band from 0.25 up to 0.5 nm is higher than the 2 nd and 3 rd ones.

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Direct observation of mosaic blocks in highly oriented pyrolytic graphite

Cited by 31 publications

References 3 publications

<title>Dichromatic source for the application of dual-energy tissue cancellation in mammography</title>

<title>Dichromatic source for the application of dual-energy tissue cancellation in mammography</title>

X-ray topographic determination of the granular structure in a graphite mosaic crystal: a three-dimensional reconstruction

Characteristics of Pyrolytic Graphite as a Neutron Monochromator

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