The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Hideo Hirayama - One of the best experts on this subject based on the ideXlab platform.
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transformation of a system consisting of plane Isotropic Source and unit sphere detector into a system consisting of point Isotropic Source and plane detector in monte carlo radiation transport calculation
Journal of Nuclear Science and Technology, 2012Co-Authors: Yoshihito Namito, Hajime Nakamura, A Toyoda, K Iijima, Hiroshi Iwase, Hideo HirayamaAbstract:In a nuclear power plant accident, radioactive nuclides may be released which are distributed uniformly on the ground. If estimation of dose rate from such a Source by a Monte Carlo calculation is attempted, some difficulty is encountered because the calculation efficiency is very low. To solve this low efficiency problem, we show that a plane Isotropic Source can be transformed into a point Isotropic Source by changing the detector shape from a unit sphere to a plane. We verified the validity of this transformation by the numerical comparison of unscattered photon fluence. As an example of this transformation, the ambient dose rate D i was calculated from the uniform radioactive nuclide distribution on the ground using the EGS5 Monte Carlo code. We also measured the radioactivity and ambient dose rate (M) on the KEK campus within a month after the releases from the Fukushima No. 1 Nuclear Power Plant accident. Using radioactivity data and D i, we calculated the ambient dose rate (C). The calculated and m...
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Gamma-Ray Buildup Factors for a Point Isotropic Source in the Single Layer Shield by Using BERMUDA Code
Journal of Nuclear Science and Technology, 2000Co-Authors: Yukio Sakamoto, Tomoo Suzuki, Osamu Sato, Hideo HirayamaAbstract:In order to modify the standard data of gamma-ray buildup factors for a point Isotropic Source in the single layer, the applicability of the direct integration method code BERMUDA to buildup factor calculations was surveyed. In this code, group-angle transfer matrix of photons is calculated by numerically integrating the Klein-Nishina formula for Compton scattering taking the energy-angle correlation into account. In the low energy region, the four K-shell fluorescence are considered whose Isotropic emission intensity can be calculated from the primary photon intensity, the K-shell absorption cross section data and fluorescence yield. In the higher energy region for high-Z materials, the Bremsstrahlung is considered whose energy-angle production correlation matrixes were obtained by EGS4 code. The exposure buildup factors of lead for low energy photons calculated by using BERMUDA code without and with fluorescence were good agreement with those by EGS4 and PALLAS codes. Those of lead for high energy photo...
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An Improved Approximation Formula of Gamma-Ray Buildup Factors for a Point Isotropic Source in Two-Layer Shields
Journal of Nuclear Science and Technology, 2000Co-Authors: Yoshiko Harima, Yukio Sakamoto, Naohiro Kurosawa, Hideo HirayamaAbstract:An approximation formula of buildup factor for two-layer shields proposed previously was improved to fitting to the newly calculated buildup factors for point Isotropic Source gamma-rays of 0.1, 0.3, 0.6, 1,3,6 and 10 MeV penetrating two-layer shields combinations of water, iron or lead materials with the Monte Carlo code EGS4 included the effects of Bremsstrahlung and fluorescent radiations. A f-function in the formula was modified to reproduce precisely the reference data up to the total thickness 40 mfp and the value of buildup factor at the interface of two-layer shields. The functions α and β used in improved f-function f(x1,x2) = α(x1)/{α(x1)+B2(x1)*β(x1,x2)x2} were represented by simple formula fitted to reference data in excellent agreement. Consequently, the two-layer shields buildup factor for any arbitrary thickness of the first-layer x1, and the second-layer x2, and for arbitrary Source energy can easily be estimated by interpolation of functions α and β with respect to energy.
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Approximating Model for Multilayer Gamma-Ray Buildup Factors by Transmission Matrix Method: Application to Point Isotropic Source Geometry
Nuclear Science and Engineering, 1995Co-Authors: Kazuo Shin, Hideo HirayamaAbstract:An approximating formula recently proposed by the authors for gamma-ray buildup factors of multilayered shields is applied to point Isotropic Source problems. The formula, which is formulated in vector form with a four-group approximation, handles the gamma-ray energy spectrum directly and uses the transmission and albedo matrices to take gamma-ray transmission and backscattering effects into consideration. The gamma-ray transmission and back-scattering probabilities through a 1-mean-free-path- (mfp-) thick shell depend on the shell curvature. This phenomenon plays an important role in simulating the gamma-ray buildup factor in point Isotropic Source geometry. In this model, the dependence is described by simplified expressions. The feasibility of the formula for systematically describing the point Isotropic buildup factors was tested by using buildup factors calculated by the Monte Carlo method as reference data. The materials used in the tests were water, iron, and lead, and the Source energies assumed were 0.5, 1, and 10 MeV. Through the tests, the method was found to reproduce the reference data of double-layered shields of these materials very well. With the same parameters, the buildup factors of three-layered shields are also reproducible. Buildup factors computed with two different group structures were examined to test the adequacy of the energymore » group structure adopted. The group structure previously adopted was found to be adequate in the energy range of 0.5 to 10 MeV.« less
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A new approximating model for gamma-ray buildup factors of stratified shields
Nuclear Science and Engineering, 1994Co-Authors: Kazuo Shin, Hideo HirayamaAbstract:A new approximate expression for gamma-ray buildup factors of multilayered shields is proposed. The expression is formulated based on the vector form and considers the gamma-ray energy spectrum directly. It treats the gamma-ray transmission by a transmission matrix and the backscattering by an albedo matrix. Its capability of reproducing the buildup factors for multilayered shields is demonstrate by using double-layered shields composed of two materials of water, iron, and lead at 1 and 10 MeV. The data of three-layered shields of these materials are also very well reproduced. The mechanism of the density effect arising, which appears in the buildup factor for a point Isotropic Source, is clearly interpreted by the current method to be a geometrical effect. A correction factor for incorporating the density effect into the current expression is derived. The modified expression is successfully applied to buildup factors for a 0.5-MeV point Isotropic Source for two-layered shields of water and iron.
Jeanjacques Greffet - One of the best experts on this subject based on the ideXlab platform.
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coherent spontaneous emission of light by thermal Sources
Physical Review B, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques Greffet, Yong ChenAbstract:The emission of light by a material at temperature T has been shown recently to be coherent in the near field. These properties were attributed to the thermal excitation of surface polaritons. We review the origin of this phenomenon. We analyze the influence of the microstructure and temperature on the coherence properties and show how to engineer thermoradiative properties of surfaces. We report the design of a quasi-Isotropic Source and a very directional Source of thermal light. We also report a measurement of the transverse coherence length of a thermal Source of light.
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Coherent spontaneous emission of light by thermal Sources
Physical Review B: Condensed Matter and Materials Physics, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques GreffetAbstract:The emission of light by a material at temperature T has been shown recently to be coherent in the near field. Theses propertis were attributed to the thermal excitation of surface polaritons. We review the origin of this phenomenon. We analyze the influrence of the microstructure and temperature on the coherence properties and show how to engineer thermoradiative properties of surfaces. We report the design of a quasi-Isotropic Source and a very directional Source of thermal light. We also report a measurement of the transverse coherence lenght of a thermal Source of light.
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Engineering infrared emission properties of silicon in the near field and the far field
Optics Communications, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques GreffetAbstract:We study numerically the thermal emission of highly doped silicon surfaces. We show that by modifying the doping, we can tune the frequency of emission. We also show that by taking advantage of the large local density of states due to surface-plasmon polaritons, radiative properties in the far field can be drastically modified. It is possible to realize a spatially partially coherent thermal Source as well as a quasi-Isotropic Source. Finally, we study the radiatve transfer between two doped silicon bodies. Surface-plasmon polaritons produce an enhancement of several orders of magnitude of the radiative energy transfer at nanometric distances.
Francois Marquier - One of the best experts on this subject based on the ideXlab platform.
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coherent spontaneous emission of light by thermal Sources
Physical Review B, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques Greffet, Yong ChenAbstract:The emission of light by a material at temperature T has been shown recently to be coherent in the near field. These properties were attributed to the thermal excitation of surface polaritons. We review the origin of this phenomenon. We analyze the influence of the microstructure and temperature on the coherence properties and show how to engineer thermoradiative properties of surfaces. We report the design of a quasi-Isotropic Source and a very directional Source of thermal light. We also report a measurement of the transverse coherence length of a thermal Source of light.
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Coherent spontaneous emission of light by thermal Sources
Physical Review B: Condensed Matter and Materials Physics, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques GreffetAbstract:The emission of light by a material at temperature T has been shown recently to be coherent in the near field. Theses propertis were attributed to the thermal excitation of surface polaritons. We review the origin of this phenomenon. We analyze the influrence of the microstructure and temperature on the coherence properties and show how to engineer thermoradiative properties of surfaces. We report the design of a quasi-Isotropic Source and a very directional Source of thermal light. We also report a measurement of the transverse coherence lenght of a thermal Source of light.
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Engineering infrared emission properties of silicon in the near field and the far field
Optics Communications, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques GreffetAbstract:We study numerically the thermal emission of highly doped silicon surfaces. We show that by modifying the doping, we can tune the frequency of emission. We also show that by taking advantage of the large local density of states due to surface-plasmon polaritons, radiative properties in the far field can be drastically modified. It is possible to realize a spatially partially coherent thermal Source as well as a quasi-Isotropic Source. Finally, we study the radiatve transfer between two doped silicon bodies. Surface-plasmon polaritons produce an enhancement of several orders of magnitude of the radiative energy transfer at nanometric distances.
Jeanphilippe Mulet - One of the best experts on this subject based on the ideXlab platform.
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coherent spontaneous emission of light by thermal Sources
Physical Review B, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques Greffet, Yong ChenAbstract:The emission of light by a material at temperature T has been shown recently to be coherent in the near field. These properties were attributed to the thermal excitation of surface polaritons. We review the origin of this phenomenon. We analyze the influence of the microstructure and temperature on the coherence properties and show how to engineer thermoradiative properties of surfaces. We report the design of a quasi-Isotropic Source and a very directional Source of thermal light. We also report a measurement of the transverse coherence length of a thermal Source of light.
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Coherent spontaneous emission of light by thermal Sources
Physical Review B: Condensed Matter and Materials Physics, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques GreffetAbstract:The emission of light by a material at temperature T has been shown recently to be coherent in the near field. Theses propertis were attributed to the thermal excitation of surface polaritons. We review the origin of this phenomenon. We analyze the influrence of the microstructure and temperature on the coherence properties and show how to engineer thermoradiative properties of surfaces. We report the design of a quasi-Isotropic Source and a very directional Source of thermal light. We also report a measurement of the transverse coherence lenght of a thermal Source of light.
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Engineering infrared emission properties of silicon in the near field and the far field
Optics Communications, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques GreffetAbstract:We study numerically the thermal emission of highly doped silicon surfaces. We show that by modifying the doping, we can tune the frequency of emission. We also show that by taking advantage of the large local density of states due to surface-plasmon polaritons, radiative properties in the far field can be drastically modified. It is possible to realize a spatially partially coherent thermal Source as well as a quasi-Isotropic Source. Finally, we study the radiatve transfer between two doped silicon bodies. Surface-plasmon polaritons produce an enhancement of several orders of magnitude of the radiative energy transfer at nanometric distances.
Karl Joulain - One of the best experts on this subject based on the ideXlab platform.
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coherent spontaneous emission of light by thermal Sources
Physical Review B, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques Greffet, Yong ChenAbstract:The emission of light by a material at temperature T has been shown recently to be coherent in the near field. These properties were attributed to the thermal excitation of surface polaritons. We review the origin of this phenomenon. We analyze the influence of the microstructure and temperature on the coherence properties and show how to engineer thermoradiative properties of surfaces. We report the design of a quasi-Isotropic Source and a very directional Source of thermal light. We also report a measurement of the transverse coherence length of a thermal Source of light.
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Coherent spontaneous emission of light by thermal Sources
Physical Review B: Condensed Matter and Materials Physics, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques GreffetAbstract:The emission of light by a material at temperature T has been shown recently to be coherent in the near field. Theses propertis were attributed to the thermal excitation of surface polaritons. We review the origin of this phenomenon. We analyze the influrence of the microstructure and temperature on the coherence properties and show how to engineer thermoradiative properties of surfaces. We report the design of a quasi-Isotropic Source and a very directional Source of thermal light. We also report a measurement of the transverse coherence lenght of a thermal Source of light.
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Engineering infrared emission properties of silicon in the near field and the far field
Optics Communications, 2004Co-Authors: Francois Marquier, Karl Joulain, Jeanphilippe Mulet, Remi Carminati, Jeanjacques GreffetAbstract:We study numerically the thermal emission of highly doped silicon surfaces. We show that by modifying the doping, we can tune the frequency of emission. We also show that by taking advantage of the large local density of states due to surface-plasmon polaritons, radiative properties in the far field can be drastically modified. It is possible to realize a spatially partially coherent thermal Source as well as a quasi-Isotropic Source. Finally, we study the radiatve transfer between two doped silicon bodies. Surface-plasmon polaritons produce an enhancement of several orders of magnitude of the radiative energy transfer at nanometric distances.
