The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Werner Jark - One of the best experts on this subject based on the ideXlab platform.
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on obtaining high spectral resolution in extreme ultraviolet soft x ray monochromators operating off plane diffraction in a divergent Incident Beam
Journal of Synchrotron Radiation, 2020Co-Authors: Werner JarkAbstract:When the trajectory of an Incident Beam is oriented parallel to the grooves of a periodic grating structure the radiation Beam is diffracted off-plane orthogonal to the plane of incidence. The diffraction efficiency in this condition is very high and in a grating with a sawtooth profile it can approach the reflection coefficient for a simple mirror, when the diffraction order of interest follows the direction for specular reflection at the flat part of the steps. When this concept is used in a plane grating in a monochromator for synchrotron radiation sources, the Incident Beam is almost always collimated in order to minimize any deterioration of the Beam properties due to aberrations, which will be introduced in the diffraction process when an uncollimated Beam is used. These aberrations are very severe when the groove density is constant. It will be shown that the effect of these aberrations can be corrected after the diffraction by the use of astigmatic focusing. The latter can be provided by a crossed mirror pair with different focal lengths in the corresponding orthogonal directions. Then a monochromator based on this concept can provide source size limited spectral resolution in an uncollimated Incident Beam. This is identical to the spectral resolution that can be provided by the same grating when operated at the same position in a collimated Incident Beam. The source size limited spectral resolution in this case corresponds to a high spectral resolving power of better than ΔE/E = 10 000 for photon energies around 300 eV in the soft X-ray range.
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On obtaining high spectral resolution in extreme ultraviolet/soft X-ray monochromators operating off-plane diffraction in a divergent Incident Beam.
Journal of Synchrotron Radiation, 2020Co-Authors: Werner JarkAbstract:When the trajectory of an Incident Beam is oriented parallel to the grooves of a periodic grating structure the radiation Beam is diffracted off-plane orthogonal to the plane of incidence. The diffraction efficiency in this condition is very high and in a grating with a sawtooth profile it can approach the reflection coefficient for a simple mirror, when the diffraction order of interest follows the direction for specular reflection at the flat part of the steps. When this concept is used in a plane grating in a monochromator for synchrotron radiation sources, the Incident Beam is almost always collimated in order to minimize any deterioration of the Beam properties due to aberrations, which will be introduced in the diffraction process when an uncollimated Beam is used. These aberrations are very severe when the groove density is constant. It will be shown that the effect of these aberrations can be corrected after the diffraction by the use of astigmatic focusing. The latter can be provided by a crossed mirror pair with different focal lengths in the corresponding orthogonal directions. Then a monochromator based on this concept can provide source size limited spectral resolution in an uncollimated Incident Beam. This is identical to the spectral resolution that can be provided by the same grating when operated at the same position in a collimated Incident Beam. The source size limited spectral resolution in this case corresponds to a high spectral resolving power of better than ΔE/E = 10 000 for photon energies around 300 eV in the soft X-ray range.
M. Segev - One of the best experts on this subject based on the ideXlab platform.
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Electroholographic tunable volume grating in the g44 configuration.
Optics letters, 2006Co-Authors: Assaf Bitman, Lavi Secundo, Guy Bartal, Noam Sapiens, Aharon J. Agranat, M. SegevAbstract:The g(44) grating is an electroholographic transmission grating in which the applied field is perpendicular to both the grating vector and the wave vector of the Incident Beam. It is argued that in this configuration the Incident Beam traverses through a periodically rotating index ellipsoid. It is shown that in the g(44) configuration the Bragg condition is fulfilled for a specific value of the applied field and for a diffracting Beam polarization that is perpendicular to that of the Incident Beam. Consequently, the g(44) grating can be used as an electrically controlled filter. Tunability of 7 nm is demonstrated in a 2mm thick grating.
P. Van Houtte - One of the best experts on this subject based on the ideXlab platform.
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Comparative measurement of residual stress in diamond coatings by low-Incident-Beam-angle-diffraction and micro-Raman spectroscopy
Journal of Materials Research, 1996Co-Authors: Hardy Mohrbacher, K. Van Acker, P. Van Houtte, Bart Blanpain, Jean Pierre CelisAbstract:Two experimental techniques for the quantitative measurement of residual stress in thin polycrystalline diamond coatings have been developed. The x-ray low-Incident-Beam-angle-diffraction (LIBAD) allows one to measure the lattice strain with well-defined in-depth information, while micro-Raman spectroscopy permits one to accurately measure the frequencies of the zone-center optical phonons of diamond which are related to the lattice strain. The interpretation of the measured information in terms of residual stress is outlined for both techniques. The residual stress data obtained by either method in thin CVD diamond coatings were found to be in excellent agreement. The sign and magnitude of the balanced biaxial stress in the coating plane depend mainly on the substrate material used for the diamond deposition. Compressive stress was present in diamond coatings deposited on WC-Co substrates, whereas tensile stress was found in those on SiAlON substrates.
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Characterization of thin nickel electrocoatings by the low-Incident-Beam-angle diffraction method
Journal of Applied Crystallography, 1994Co-Authors: K. Van Acker, L. De Buyser, Jean Pierre Celis, P. Van HoutteAbstract:The low-Incident-Beam-angle diffraction technique (LIBAD) has been developed as a powerful X-ray diffraction tool for the characterization of thin crystalline coatings. The technique can be implemented to determine the residual stress state in thin coatings, their crystallographic texture, by means of the orientation distribution function, and thickness, as well as the stress profile in a coating as a function of depth. As an example, electrodeposited nickel coatings on a copper substrate have been characterized with this technique for thicknesses varying from 0.6 to 3.8 μm. Crystallographic texture and mean residual stress appear to be correlated with the coating thickness. So, for example, the residual stress of the coatings evolves from a low to a high tensile stress with increasing coating thickness. The stress in the uppermost region of the substrate is influenced by the stress state in the coating. The stress profile in the coating was found to be linearly dependent on the information depth.
Jean Pierre Celis - One of the best experts on this subject based on the ideXlab platform.
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Comparative measurement of residual stress in diamond coatings by low-Incident-Beam-angle-diffraction and micro-Raman spectroscopy
Journal of Materials Research, 1996Co-Authors: Hardy Mohrbacher, K. Van Acker, P. Van Houtte, Bart Blanpain, Jean Pierre CelisAbstract:Two experimental techniques for the quantitative measurement of residual stress in thin polycrystalline diamond coatings have been developed. The x-ray low-Incident-Beam-angle-diffraction (LIBAD) allows one to measure the lattice strain with well-defined in-depth information, while micro-Raman spectroscopy permits one to accurately measure the frequencies of the zone-center optical phonons of diamond which are related to the lattice strain. The interpretation of the measured information in terms of residual stress is outlined for both techniques. The residual stress data obtained by either method in thin CVD diamond coatings were found to be in excellent agreement. The sign and magnitude of the balanced biaxial stress in the coating plane depend mainly on the substrate material used for the diamond deposition. Compressive stress was present in diamond coatings deposited on WC-Co substrates, whereas tensile stress was found in those on SiAlON substrates.
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Characterization of thin nickel electrocoatings by the low-Incident-Beam-angle diffraction method
Journal of Applied Crystallography, 1994Co-Authors: K. Van Acker, L. De Buyser, Jean Pierre Celis, P. Van HoutteAbstract:The low-Incident-Beam-angle diffraction technique (LIBAD) has been developed as a powerful X-ray diffraction tool for the characterization of thin crystalline coatings. The technique can be implemented to determine the residual stress state in thin coatings, their crystallographic texture, by means of the orientation distribution function, and thickness, as well as the stress profile in a coating as a function of depth. As an example, electrodeposited nickel coatings on a copper substrate have been characterized with this technique for thicknesses varying from 0.6 to 3.8 μm. Crystallographic texture and mean residual stress appear to be correlated with the coating thickness. So, for example, the residual stress of the coatings evolves from a low to a high tensile stress with increasing coating thickness. The stress in the uppermost region of the substrate is influenced by the stress state in the coating. The stress profile in the coating was found to be linearly dependent on the information depth.
Assaf Bitman - One of the best experts on this subject based on the ideXlab platform.
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Electroholographic tunable volume grating in the g44 configuration.
Optics letters, 2006Co-Authors: Assaf Bitman, Lavi Secundo, Guy Bartal, Noam Sapiens, Aharon J. Agranat, M. SegevAbstract:The g(44) grating is an electroholographic transmission grating in which the applied field is perpendicular to both the grating vector and the wave vector of the Incident Beam. It is argued that in this configuration the Incident Beam traverses through a periodically rotating index ellipsoid. It is shown that in the g(44) configuration the Bragg condition is fulfilled for a specific value of the applied field and for a diffracting Beam polarization that is perpendicular to that of the Incident Beam. Consequently, the g(44) grating can be used as an electrically controlled filter. Tunability of 7 nm is demonstrated in a 2mm thick grating.
