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P Gouttebroze - One of the best experts on this subject based on the ideXlab platform.
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radiative transfer in cylindrical threads with Incident Radiation vi a hydrogen plus helium system
Astronomy and Astrophysics, 2009Co-Authors: P Gouttebroze, Nicolas LabrosseAbstract:Context: Spectral lines of helium are commonly observed on the Sun. These observations contain important information about physical conditions and He/H abundance variations within solar outer structures. Aims: The modeling of chromospheric and coronal loop-like structures visible in hydrogen and helium lines requires the use of appropriate diagnostic tools based on NLTE radiative tranfer in cylindrical geometry. Methods: We use iterative numerical methods to solve the equations of NLTE radiative transfer and statistical equilibrium of atomic level populations. These equations are solved alternatively for hydrogen and helium atoms, using cylindrical coordinates and prescribed solar Incident Radiation. Electron density is determined by the ionization equilibria of both atoms. Two-dimensional effects are included. Results: The mechanisms of formation of the principal helium lines are analyzed and the sources of emission inside the cylinder are located. The variations of spectral line intensities with temperature, pressure, and helium abundance, are studied. Conclusions: The simultaneous computation of hydrogen and helium lines, performed by the new numerical code, allows the construction of loop models including an extended range of temperatures.
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Radiative transfer in cylindrical threads with Incident Radiation VI. A hydrogen plus helium system
Astronomy & Astrophysics, 2009Co-Authors: P Gouttebroze, Nicolas LabrosseAbstract:Spectral lines of helium are commonly observed on the Sun. These observations contain important informations about physical conditions and He/H abundance variations within solar outer structures. The modeling of chromospheric and coronal loop-like structures visible in hydrogen and helium lines requires the use of appropriate diagnostic tools based on NLTE radiative tranfer in cylindrical geometry. We use iterative numerical methods to solve the equations of NLTE radiative transfer and statistical equilibrium of atomic level populations. These equations are solved alternatively for the hydrogen and helium atoms, using cylindrical coordinates and prescribed solar Incident Radiation. Electron density is determined by the ionization equilibria of both atoms. Two-dimension effects are included. The mechanisms of formation of the principal helium lines are analyzed and the sources of emission inside the cylinder are located. The variations of spectral line intensities with temperature, pressure, and helium abundance, are studied. The simultaneous computation of hydrogen and helium lines, performed by the new numerical code, allows the construction of loop models including an extended range of temperatures.
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Radiative transfer in cylindrical threads with Incident Radiation V. 2D transfer with 3D velocity fields
Astronomy & Astrophysics, 2008Co-Authors: P GouttebrozeAbstract:Context. Time-resolved observations of loops embedded in the solar corona show the existence of motions of matter inside these structures, as well as the global motions of these objects themselves. Aims. We have developed a modeling tool for cylindrical objects inside the solar corona, including 2-dimensional (azimuth-dependent) radiative transfer effects and 3-dimensional velocity fields. Methods. We used numerical methods to simultaneously solve the equations of NLTE radiative transfer, statistical equilibrium of hydrogen level populations, and electric neutrality. The radiative transfer equations were solved using cylindrical coordinates and prescribed solar Incident Radiation. In addition to the effects of anisotropic Incident Radiation, treated in previous papers, we took into account the Doppler shifts produced by a 3-dimension velocity field. Results. The effects of different types of velocity fields on hydrogen line profiles and intensities are described. Motions include loop oscillations, rotation, and longitudinal flows, which produce different deformations of profiles. Doppler brightening and dimming effects are also observed. Conclusions. This is a new step in the diagnostic of physical conditions in coronal loops, allowing the study of dynamical phenomena.
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Radiative transfer in cylindrical threads with Incident Radiation - III. Hydrogen spectrum
Astronomy & Astrophysics, 2006Co-Authors: P GouttebrozeAbstract:A numerical code is proposed for the solution of NLTE radiative transfer equations in long cylinders, including multilevel atoms and anisotropic Incident Radiation (which implies a 2-dimension treatment of the Radiation field). It is applied to the modelling of the hydrogen spectrum emitted by magnetic loops imbedded in the solar corona. The model hydrogen atom includes 10 levels and one continuum. The intensities emitted by loops in the most important hydrogen lines and in the Lyman continuum are discussed using a set of isothermal and isobaric models. The case of loops with a radial temperature gradient is also investigated.
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Radiative transfer in cylindrical threads with Incident Radiation - II. 2D azimuth-dependent case
Astronomy & Astrophysics, 2005Co-Authors: P GouttebrozeAbstract:A method is proposed for the solution of NLTE radiative transfer equations in long cylinders with an external Incident Radiation that varies with direction. This method is designed principally for the modelling of elongated structures imbedded in the solar corona (loops, prominence threads). The radiative transfer problem under consideration is a 2D one, since the source functions and absorption coefficients vary with both distance to axis and azimuth. The method is based on the general principles of finite-differences and accelerated Λ -iteration. A Fourier series is used for interpolation in azimuth. The method is applied to a line emitted by a two-level atom with complete frequency redistribution. Convergence properties of the method and influence of the inclination angle on the source function are discussed.
Priyanka Singh - One of the best experts on this subject based on the ideXlab platform.
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effect of spatial variation of Incident Radiation on spectral response of a large area silicon solar cell and the cell parameters determined from it
Solar Energy Materials and Solar Cells, 2003Co-Authors: Priyanka Singh, Ravi Kumar, P.n Vinod, B. C. Chakravarty, S N SinghAbstract:Effect of spatial variation of Incident monochromatic light on spectral response of an n+–p–p+ silicon solar cell and determination of diffusion length of minority carriers (Lb) in the base region and the thickness of the apparent dead layer (xd) in the n+ emitter from the spectral response have been investigated. Spectral response of a few 10 cm diameter and 10×10 cm2 pseudo-square silicon solar cells was measured with the help of a standard silicon solar cell of 2×2 cm2 area in 400–1100 nm wavelength range. Different areas (4, 9, 16, 25 and total area 78.6 or 96 cm2) were exposed. The effect of the radial variation of Incident Radiation was determined quantitatively by defining a parameter f1 as the ratio of the average intensity falling on the reference cell to that on the exposed area of the test cell. The value of f1 varied between 1 and 1.15 (1.25) as the exposed area of the cell varied from 4 cm2 to 78.6 (96) cm2 indicating that the spatial inhomogeneity of intensity increased with the increase in the exposed cell area. Short-circuit current densities, Jsc, computed from spectral response data for AM1.5 spectrum were less compared to the directly measured values by a factor which was nearly equal to f1. However, radial variation of intensity does not affect the determination of diffusion length of minority carriers in the base region (by the long wavelength spectral response, LWSR method using the measured spectral response data in 0.85<λ<1.05 μm range) and the thickness of the dead layer (by the method of Singh et al. using the data of 0.45<λ<0.65 μm range) significantly.
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Effect of spatial variation of Incident Radiation on spectral response of a large area silicon solar cell and the cell parameters determined from it
Solar Energy Materials and Solar Cells, 2003Co-Authors: Priyanka Singh, Ravi Kumar, P.n Vinod, B. C. Chakravarty, SinghAbstract:Effect of spatial variation of Incident monochromatic light on spectral response of an n+–p–p+ silicon solar cell and determination of diffusion length of minority carriers (Lb) in the base region and the thickness of the apparent dead layer (xd) in the n+ emitter from the spectral response have been investigated. Spectral response of a few 10 cm diameter and 10×10 cm2 pseudo-square silicon solar cells was measured with the help of a standard silicon solar cell of 2×2 cm2 area in 400–1100 nm wavelength range. Different areas (4, 9, 16, 25 and total area 78.6 or 96 cm2) were exposed. The effect of the radial variation of Incident Radiation was determined quantitatively by defining a parameter f1 as the ratio of the average intensity falling on the reference cell to that on the exposed area of the test cell. The value of f1 varied between 1 and 1.15 (1.25) as the exposed area of the cell varied from 4 cm2 to 78.6 (96) cm2 indicating that the spatial inhomogeneity of intensity increased with the increase in the exposed cell area. Short-circuit current densities, Jsc, computed from spectral response data for AM1.5 spectrum were less compared to the directly measured values by a factor which was nearly equal to f1. However, radial variation of intensity does not affect the determination of diffusion length of minority carriers in the base region (by the long wavelength spectral response, LWSR method using the measured spectral response data in 0.85
Singh - One of the best experts on this subject based on the ideXlab platform.
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Effect of spatial variation of Incident Radiation on spectral response of a large area silicon solar cell and the cell parameters determined from it
Solar Energy Materials and Solar Cells, 2003Co-Authors: Priyanka Singh, Ravi Kumar, P.n Vinod, B. C. Chakravarty, SinghAbstract:Effect of spatial variation of Incident monochromatic light on spectral response of an n+–p–p+ silicon solar cell and determination of diffusion length of minority carriers (Lb) in the base region and the thickness of the apparent dead layer (xd) in the n+ emitter from the spectral response have been investigated. Spectral response of a few 10 cm diameter and 10×10 cm2 pseudo-square silicon solar cells was measured with the help of a standard silicon solar cell of 2×2 cm2 area in 400–1100 nm wavelength range. Different areas (4, 9, 16, 25 and total area 78.6 or 96 cm2) were exposed. The effect of the radial variation of Incident Radiation was determined quantitatively by defining a parameter f1 as the ratio of the average intensity falling on the reference cell to that on the exposed area of the test cell. The value of f1 varied between 1 and 1.15 (1.25) as the exposed area of the cell varied from 4 cm2 to 78.6 (96) cm2 indicating that the spatial inhomogeneity of intensity increased with the increase in the exposed cell area. Short-circuit current densities, Jsc, computed from spectral response data for AM1.5 spectrum were less compared to the directly measured values by a factor which was nearly equal to f1. However, radial variation of intensity does not affect the determination of diffusion length of minority carriers in the base region (by the long wavelength spectral response, LWSR method using the measured spectral response data in 0.85
S N Singh - One of the best experts on this subject based on the ideXlab platform.
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effect of spatial variation of Incident Radiation on spectral response of a large area silicon solar cell and the cell parameters determined from it
Solar Energy Materials and Solar Cells, 2003Co-Authors: Priyanka Singh, Ravi Kumar, P.n Vinod, B. C. Chakravarty, S N SinghAbstract:Effect of spatial variation of Incident monochromatic light on spectral response of an n+–p–p+ silicon solar cell and determination of diffusion length of minority carriers (Lb) in the base region and the thickness of the apparent dead layer (xd) in the n+ emitter from the spectral response have been investigated. Spectral response of a few 10 cm diameter and 10×10 cm2 pseudo-square silicon solar cells was measured with the help of a standard silicon solar cell of 2×2 cm2 area in 400–1100 nm wavelength range. Different areas (4, 9, 16, 25 and total area 78.6 or 96 cm2) were exposed. The effect of the radial variation of Incident Radiation was determined quantitatively by defining a parameter f1 as the ratio of the average intensity falling on the reference cell to that on the exposed area of the test cell. The value of f1 varied between 1 and 1.15 (1.25) as the exposed area of the cell varied from 4 cm2 to 78.6 (96) cm2 indicating that the spatial inhomogeneity of intensity increased with the increase in the exposed cell area. Short-circuit current densities, Jsc, computed from spectral response data for AM1.5 spectrum were less compared to the directly measured values by a factor which was nearly equal to f1. However, radial variation of intensity does not affect the determination of diffusion length of minority carriers in the base region (by the long wavelength spectral response, LWSR method using the measured spectral response data in 0.85<λ<1.05 μm range) and the thickness of the dead layer (by the method of Singh et al. using the data of 0.45<λ<0.65 μm range) significantly.
B. C. Chakravarty - One of the best experts on this subject based on the ideXlab platform.
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effect of spatial variation of Incident Radiation on spectral response of a large area silicon solar cell and the cell parameters determined from it
Solar Energy Materials and Solar Cells, 2003Co-Authors: Priyanka Singh, Ravi Kumar, P.n Vinod, B. C. Chakravarty, S N SinghAbstract:Effect of spatial variation of Incident monochromatic light on spectral response of an n+–p–p+ silicon solar cell and determination of diffusion length of minority carriers (Lb) in the base region and the thickness of the apparent dead layer (xd) in the n+ emitter from the spectral response have been investigated. Spectral response of a few 10 cm diameter and 10×10 cm2 pseudo-square silicon solar cells was measured with the help of a standard silicon solar cell of 2×2 cm2 area in 400–1100 nm wavelength range. Different areas (4, 9, 16, 25 and total area 78.6 or 96 cm2) were exposed. The effect of the radial variation of Incident Radiation was determined quantitatively by defining a parameter f1 as the ratio of the average intensity falling on the reference cell to that on the exposed area of the test cell. The value of f1 varied between 1 and 1.15 (1.25) as the exposed area of the cell varied from 4 cm2 to 78.6 (96) cm2 indicating that the spatial inhomogeneity of intensity increased with the increase in the exposed cell area. Short-circuit current densities, Jsc, computed from spectral response data for AM1.5 spectrum were less compared to the directly measured values by a factor which was nearly equal to f1. However, radial variation of intensity does not affect the determination of diffusion length of minority carriers in the base region (by the long wavelength spectral response, LWSR method using the measured spectral response data in 0.85<λ<1.05 μm range) and the thickness of the dead layer (by the method of Singh et al. using the data of 0.45<λ<0.65 μm range) significantly.
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Effect of spatial variation of Incident Radiation on spectral response of a large area silicon solar cell and the cell parameters determined from it
Solar Energy Materials and Solar Cells, 2003Co-Authors: Priyanka Singh, Ravi Kumar, P.n Vinod, B. C. Chakravarty, SinghAbstract:Effect of spatial variation of Incident monochromatic light on spectral response of an n+–p–p+ silicon solar cell and determination of diffusion length of minority carriers (Lb) in the base region and the thickness of the apparent dead layer (xd) in the n+ emitter from the spectral response have been investigated. Spectral response of a few 10 cm diameter and 10×10 cm2 pseudo-square silicon solar cells was measured with the help of a standard silicon solar cell of 2×2 cm2 area in 400–1100 nm wavelength range. Different areas (4, 9, 16, 25 and total area 78.6 or 96 cm2) were exposed. The effect of the radial variation of Incident Radiation was determined quantitatively by defining a parameter f1 as the ratio of the average intensity falling on the reference cell to that on the exposed area of the test cell. The value of f1 varied between 1 and 1.15 (1.25) as the exposed area of the cell varied from 4 cm2 to 78.6 (96) cm2 indicating that the spatial inhomogeneity of intensity increased with the increase in the exposed cell area. Short-circuit current densities, Jsc, computed from spectral response data for AM1.5 spectrum were less compared to the directly measured values by a factor which was nearly equal to f1. However, radial variation of intensity does not affect the determination of diffusion length of minority carriers in the base region (by the long wavelength spectral response, LWSR method using the measured spectral response data in 0.85
