The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
A. V. Serov - One of the best experts on this subject based on the ideXlab platform.
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Transition radiation detectors with a Dihedral Angle or a cone as a radiator
Physics of Particles and Nuclei Letters, 2014Co-Authors: A. V. SerovAbstract:The spectral and angular distributions of the transition radiation produced by a charge crossing an interface shaped like a Dihedral Angle or a cone are considered. The effects of the variation in the Dihedral Angle and cone Angle, the location of the crossing point on the interface, and the direction of the charge motion on the spatial distribution of the radiation are discussed. The radiation characteristics of the particles that are incident on the interface and those leaving it are given. The features of transition-radiation detectors with Dihedral-Angle or cone radiators and detectors with plane-surface radiators are compared.
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spatial distribution of transition radiation of relativistic particles in the Dihedral Angle formed by perfectly conductive planes
Bulletin of the Lebedev Physics Institute, 2012Co-Authors: A. V. Koltsov, A. V. SerovAbstract:Spatial distributions of transition radiation intensity of particles entering the Dihedral Angle and escaping from it are calculated. It was shown that radiation of escaping charge at any opening of the Dihedral Angle α is concentrated near the motion direction. If the particle enters the Angle, the radiation distribution is defined by the opening Angle. At opening Angles α = π/n, radiation is concentrated near the direction of actual charge motion when n is an even number and near the direction of image charge motion when n is an odd number. At other opening Angles, the spatial distribution of entering particle radiation has two maxima whose positions are defined by the injection Angle.
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Experimental study of coherent transition radiation from relativistic electron bunches entering a Dihedral Angle
Journal of Experimental and Theoretical Physics, 2012Co-Authors: A. V. Koltsov, A. V. SerovAbstract:The angular distributions of the intensity of transition radiation from a bunch of relativistic electrons entering a Dihedral Angle between two conducting planes have been measured in a millimeter wavelength range. A microtron with a particle energy of 7.4 MeV is used as a source of electrons. The effect of the particle injection direction and the magnitude of the Dihedral Angle on the angular distribution of the radiation intensity has been analyzed. The measurements show that the character of the distribution of radiation from a charge entering the Dihedral Angle significantly differs from that for a charge escaping the Angle. A comparatively small change in the magnitude of the Dihedral Angle can lead to qualitative changes in the angular distribution of radiation from a charge entering the Dihedral Angle.
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peculiarities of the spectral angular distribution of transition radiation from a relativistic particle in a Dihedral Angle
Journal of Experimental and Theoretical Physics, 2011Co-Authors: A. V. Koltsov, A. V. SerovAbstract:The spatial distributions of transition radiation from relativistic particles entering and exiting the edge of a Dihedral Angle formed by perfectly conducting flat surfaces have been investigated. The angular distributions of the radiation intensity in Dihedral Angles with various opening Angles have been calculated. The angular distributions of forward radiation (when the particle exits the Dihedral Angle) and backward radiation (when the particle enters the Dihedral Angle) are shown to differ significantly.
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Transition radiation in a Dihedral Angle formed by perfectly conducting planes
Journal of Experimental and Theoretical Physics, 2009Co-Authors: A. V. Koltsov, A. V. SerovAbstract:The spatial distribution of the field of transition radiation generated by a relativistic particle flying into a Dihedral Angle formed by perfectly conducting plane surfaces is determined. The cases when particles are injected from the edge and from a plane of the Dihedral Angle are considered. The angular distributions of radiation intensity in Dihedral Angles of different values are calculated.
Daniel J Frost - One of the best experts on this subject based on the ideXlab platform.
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deformation of a crystalline aggregate with a small percentage of high Dihedral Angle liquid implications for core mantle differentiation during planetary formation
Earth and Planetary Science Letters, 2011Co-Authors: Nicolas P Walte, David C Rubie, Paul D Bons, Daniel J FrostAbstract:Abstract Core–mantle differentiation of small planetesimals has been suggested to be initiated by deformation-assisted segregation of molten Fe–S through a crystalline peridotite matrix. In this study we used two different experimental approaches to investigate the effect of varying the strain rate and of varying the Dihedral Angle of the liquid phase on liquid interconnectivity. (i) High pressure experiments were performed on simplified systems consisting of olivine plus a small percentage of liquid FeS (Dihedral Angle ~ 75°) or gold (Dihedral Angle ~ 150°) at a temperature above the FeS/Au solidus but below the silicate solidus. Samples were deformed at high pressure in a deformation-DIA multianvil press at strain rates between 10 − 3 and 10 − 6 s − 1 . (ii) Optical in situ analogue experiments on norcamphor plus H 2 O (Dihedral Angle ~ 86°) were performed at room temperature to complement the d-DIA experiments. The crystalline matrix in both the d-DIA and analogue experiments deforms by grain boundary migration assisted dislocation creep under the experimental conditions. Furthermore, the liquid pockets display a similar strain rate dependent behaviour in both sets of experiments: At high strain rates deformation is strongly localised by the liquid phase, and liquid interconnection and segregation occurs. At low strain rates the geometry of liquid pockets is controlled predominantly by surface tension and little elongation and interconnection occurs. We propose a new empirical scaling approach using the d-DIA results, which indicates that some degree of high Dihedral Angle liquid interconnection and segregation may be possible down to a few percent residual liquid under natural conditions for moderate Dihedral Angles (60°
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liquid distribution and attainment of textural equilibrium in a partially molten crystalline system with a high Dihedral Angle liquid phase
Earth and Planetary Science Letters, 2007Co-Authors: Nicolas P Walte, David C Rubie, Paul D Bons, Jens K Becker, Daniel J FrostAbstract:The evolution of a high-Dihedral-Angle liquid in a crystalline matrix, such as Fe–S melt in an olivine matrix, is of vital importance for a range of questions including planetary core–mantle differentiation. We performed hydrostatic in situ analogue experiments on norcamphor–H2O liquid, and high-temperature experiments on olivine–FeS melt to investigate the evolution of the liquid and the attainment of textural equilibrium in the liquid and the solid. The liquid distribution was dominated by large unconnected liquid pools, smaller melt lenses, and the regular occurrence of dry three-grain triple junctions. Compared to low-Dihedral-Angle systems, the liquid pockets had a very low mobility during grain growth and disequilibrium features, such as elongated liquid pools, only reequilibrated slowly. The results have several consequences for the evolving microstructure: (1) Immobile liquid pockets hinder grain boundary migration and promote abnormal grain growth; (2) The attainment of textural equilibrium in solid–liquid regions is delayed with respect to liquid-free regions; (3) Grain growth does not promote liquid pocket growth, as in low-Dihedral-Angle systems, and liquid pockets do not directly interact with each other during annealing; (4) An existing liquid network is unstable and pinches off in the long-term, even if the liquid-fraction is above the theoretical percolation threshold. With regard to this final point, percolative core–mantle differentiation through an interconnected melt network may not be a viable mechanism, even above the suggested percolation threshold of ∼ 5 vol.%.
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the effect of oxygen and sulphur on the Dihedral Angle between fe o s melt and silicate minerals at high pressure implications for martian core formation
Earth and Planetary Science Letters, 2005Co-Authors: Hidenori Terasaki, Daniel J Frost, David C Rubie, Falko LangenhorstAbstract:A crucial factor in the investigation of terrestrial planet core formation is whether or not a liquid iron-alloy can segregate from a solid silicate matrix. The interconnectivity of a core-forming liquid depends on the Dihedral Angle between liquid iron-alloy and crystalline silicates at low melt fractions. Recent experimental studies at ambient pressure have implied that liquid iron-alloy can wet an olivine matrix under conditions of high oxygen and sulphur fugacities. We have examined the effects of varying sulphur and oxygen contents on the Dihedral Angle between liquid iron-alloy and crystalline silicates up to 20 GPa. The compositions studied are applicable to core formation on both the Earth and Mars and the pressure range investigated is applicable to over 80% of the depth of the entire Martian mantle. Dihedral Angles in texturally equilibrated samples decrease with increasing sulphur content and also decrease significantly with increasing FeO content of silicates. Increasing the FeO content of silicates results in an increase in both the oxygen fugacity and oxygen solubility in the Fe–S melt. Oxygen is found to have a larger effect in reducing the Dihedral Angle than sulphur. The Dihedral Angle between metallic melt and silicate crystals in the Martian mantle would have been closer to the wetting boundary of 60° than in the Earth's interior, but it would be still too large (θ>60°) to allow percolation to occur to completion. These results show that melting of the silicate mantle is required to obtain complete metal–silicate separation, which therefore supports a magma ocean scenario for core formation on both Mars and Earth.
Philip A. Allen - One of the best experts on this subject based on the ideXlab platform.
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On the identification of textural equilibrium in rocks using Dihedral Angle measurements
Geology, 1997Co-Authors: Michael T Elliott, Dougal A. Jerram, James W. Sears, Michael C. Pope, Colin P. Stark, Michael J. Cheadle, Niels Hovius, Philip A. AllenAbstract:Three-dimensional numerical simulations have been constructed to investigate the distributions of apparent Dihedral Angles expected in unequilibrated rock textures for comparison with those expected in equilibrated rock textures. For unequilibrated, fully crystallized monomineralic rocks, the simulation shows that the distribution of apparent Dihedral Angles is nonrandom and similar to that expected from an equilibrated rock, and is largely independent of crystal shape and crystal nuclei distribution, This new distribution, together with the one previously derived for an equilibrated texture, defines a pair of apparent Dihedral Angle curves which encompass curves corresponding to any degree of textural equilibrium within a monomineralic rock. The location of a measured curve within this range allows a quantitative assessment of the degree of textural equilibrium within that rock, The simulations also show that unequilibrated, partially crystallized rocks generate apparent Dihedral Angle distributions for closed triangular pores that, depending on crystal shape, may mimic equilibrated Dihedral Angle distributions. They also indicate that unless a rock is in complete equilibrium different Dihedral Angle distributions are produced by measuring the apparent Dihedral Angles of closed triangular or open nontriangular pores, An important conclusion of this work is that apparent Dihedral Angle curves for unequilibrated textures are similar to those for equilibrated textures. Therefore care must be taken when interpreting textural equilibrium from apparent Dihedral Angle curves.
Nicolas P Walte - One of the best experts on this subject based on the ideXlab platform.
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deformation of a crystalline aggregate with a small percentage of high Dihedral Angle liquid implications for core mantle differentiation during planetary formation
Earth and Planetary Science Letters, 2011Co-Authors: Nicolas P Walte, David C Rubie, Paul D Bons, Daniel J FrostAbstract:Abstract Core–mantle differentiation of small planetesimals has been suggested to be initiated by deformation-assisted segregation of molten Fe–S through a crystalline peridotite matrix. In this study we used two different experimental approaches to investigate the effect of varying the strain rate and of varying the Dihedral Angle of the liquid phase on liquid interconnectivity. (i) High pressure experiments were performed on simplified systems consisting of olivine plus a small percentage of liquid FeS (Dihedral Angle ~ 75°) or gold (Dihedral Angle ~ 150°) at a temperature above the FeS/Au solidus but below the silicate solidus. Samples were deformed at high pressure in a deformation-DIA multianvil press at strain rates between 10 − 3 and 10 − 6 s − 1 . (ii) Optical in situ analogue experiments on norcamphor plus H 2 O (Dihedral Angle ~ 86°) were performed at room temperature to complement the d-DIA experiments. The crystalline matrix in both the d-DIA and analogue experiments deforms by grain boundary migration assisted dislocation creep under the experimental conditions. Furthermore, the liquid pockets display a similar strain rate dependent behaviour in both sets of experiments: At high strain rates deformation is strongly localised by the liquid phase, and liquid interconnection and segregation occurs. At low strain rates the geometry of liquid pockets is controlled predominantly by surface tension and little elongation and interconnection occurs. We propose a new empirical scaling approach using the d-DIA results, which indicates that some degree of high Dihedral Angle liquid interconnection and segregation may be possible down to a few percent residual liquid under natural conditions for moderate Dihedral Angles (60°
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liquid distribution and attainment of textural equilibrium in a partially molten crystalline system with a high Dihedral Angle liquid phase
Earth and Planetary Science Letters, 2007Co-Authors: Nicolas P Walte, David C Rubie, Paul D Bons, Jens K Becker, Daniel J FrostAbstract:The evolution of a high-Dihedral-Angle liquid in a crystalline matrix, such as Fe–S melt in an olivine matrix, is of vital importance for a range of questions including planetary core–mantle differentiation. We performed hydrostatic in situ analogue experiments on norcamphor–H2O liquid, and high-temperature experiments on olivine–FeS melt to investigate the evolution of the liquid and the attainment of textural equilibrium in the liquid and the solid. The liquid distribution was dominated by large unconnected liquid pools, smaller melt lenses, and the regular occurrence of dry three-grain triple junctions. Compared to low-Dihedral-Angle systems, the liquid pockets had a very low mobility during grain growth and disequilibrium features, such as elongated liquid pools, only reequilibrated slowly. The results have several consequences for the evolving microstructure: (1) Immobile liquid pockets hinder grain boundary migration and promote abnormal grain growth; (2) The attainment of textural equilibrium in solid–liquid regions is delayed with respect to liquid-free regions; (3) Grain growth does not promote liquid pocket growth, as in low-Dihedral-Angle systems, and liquid pockets do not directly interact with each other during annealing; (4) An existing liquid network is unstable and pinches off in the long-term, even if the liquid-fraction is above the theoretical percolation threshold. With regard to this final point, percolative core–mantle differentiation through an interconnected melt network may not be a viable mechanism, even above the suggested percolation threshold of ∼ 5 vol.%.
David C Rubie - One of the best experts on this subject based on the ideXlab platform.
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deformation of a crystalline aggregate with a small percentage of high Dihedral Angle liquid implications for core mantle differentiation during planetary formation
Earth and Planetary Science Letters, 2011Co-Authors: Nicolas P Walte, David C Rubie, Paul D Bons, Daniel J FrostAbstract:Abstract Core–mantle differentiation of small planetesimals has been suggested to be initiated by deformation-assisted segregation of molten Fe–S through a crystalline peridotite matrix. In this study we used two different experimental approaches to investigate the effect of varying the strain rate and of varying the Dihedral Angle of the liquid phase on liquid interconnectivity. (i) High pressure experiments were performed on simplified systems consisting of olivine plus a small percentage of liquid FeS (Dihedral Angle ~ 75°) or gold (Dihedral Angle ~ 150°) at a temperature above the FeS/Au solidus but below the silicate solidus. Samples were deformed at high pressure in a deformation-DIA multianvil press at strain rates between 10 − 3 and 10 − 6 s − 1 . (ii) Optical in situ analogue experiments on norcamphor plus H 2 O (Dihedral Angle ~ 86°) were performed at room temperature to complement the d-DIA experiments. The crystalline matrix in both the d-DIA and analogue experiments deforms by grain boundary migration assisted dislocation creep under the experimental conditions. Furthermore, the liquid pockets display a similar strain rate dependent behaviour in both sets of experiments: At high strain rates deformation is strongly localised by the liquid phase, and liquid interconnection and segregation occurs. At low strain rates the geometry of liquid pockets is controlled predominantly by surface tension and little elongation and interconnection occurs. We propose a new empirical scaling approach using the d-DIA results, which indicates that some degree of high Dihedral Angle liquid interconnection and segregation may be possible down to a few percent residual liquid under natural conditions for moderate Dihedral Angles (60°
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liquid distribution and attainment of textural equilibrium in a partially molten crystalline system with a high Dihedral Angle liquid phase
Earth and Planetary Science Letters, 2007Co-Authors: Nicolas P Walte, David C Rubie, Paul D Bons, Jens K Becker, Daniel J FrostAbstract:The evolution of a high-Dihedral-Angle liquid in a crystalline matrix, such as Fe–S melt in an olivine matrix, is of vital importance for a range of questions including planetary core–mantle differentiation. We performed hydrostatic in situ analogue experiments on norcamphor–H2O liquid, and high-temperature experiments on olivine–FeS melt to investigate the evolution of the liquid and the attainment of textural equilibrium in the liquid and the solid. The liquid distribution was dominated by large unconnected liquid pools, smaller melt lenses, and the regular occurrence of dry three-grain triple junctions. Compared to low-Dihedral-Angle systems, the liquid pockets had a very low mobility during grain growth and disequilibrium features, such as elongated liquid pools, only reequilibrated slowly. The results have several consequences for the evolving microstructure: (1) Immobile liquid pockets hinder grain boundary migration and promote abnormal grain growth; (2) The attainment of textural equilibrium in solid–liquid regions is delayed with respect to liquid-free regions; (3) Grain growth does not promote liquid pocket growth, as in low-Dihedral-Angle systems, and liquid pockets do not directly interact with each other during annealing; (4) An existing liquid network is unstable and pinches off in the long-term, even if the liquid-fraction is above the theoretical percolation threshold. With regard to this final point, percolative core–mantle differentiation through an interconnected melt network may not be a viable mechanism, even above the suggested percolation threshold of ∼ 5 vol.%.
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the effect of oxygen and sulphur on the Dihedral Angle between fe o s melt and silicate minerals at high pressure implications for martian core formation
Earth and Planetary Science Letters, 2005Co-Authors: Hidenori Terasaki, Daniel J Frost, David C Rubie, Falko LangenhorstAbstract:A crucial factor in the investigation of terrestrial planet core formation is whether or not a liquid iron-alloy can segregate from a solid silicate matrix. The interconnectivity of a core-forming liquid depends on the Dihedral Angle between liquid iron-alloy and crystalline silicates at low melt fractions. Recent experimental studies at ambient pressure have implied that liquid iron-alloy can wet an olivine matrix under conditions of high oxygen and sulphur fugacities. We have examined the effects of varying sulphur and oxygen contents on the Dihedral Angle between liquid iron-alloy and crystalline silicates up to 20 GPa. The compositions studied are applicable to core formation on both the Earth and Mars and the pressure range investigated is applicable to over 80% of the depth of the entire Martian mantle. Dihedral Angles in texturally equilibrated samples decrease with increasing sulphur content and also decrease significantly with increasing FeO content of silicates. Increasing the FeO content of silicates results in an increase in both the oxygen fugacity and oxygen solubility in the Fe–S melt. Oxygen is found to have a larger effect in reducing the Dihedral Angle than sulphur. The Dihedral Angle between metallic melt and silicate crystals in the Martian mantle would have been closer to the wetting boundary of 60° than in the Earth's interior, but it would be still too large (θ>60°) to allow percolation to occur to completion. These results show that melting of the silicate mantle is required to obtain complete metal–silicate separation, which therefore supports a magma ocean scenario for core formation on both Mars and Earth.
