The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
S. Swain - One of the best experts on this subject based on the ideXlab platform.
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Collisional-dephasing and Doppler-Broadening effects on quantum interference in a Vee atomic system
Journal of the Optical Society of America B, 1998Co-Authors: Peng Zhou, S. SwainAbstract:We investigate the effects of collisional dephasing and Doppler Broadening on the quantum beats, narrow resonances, and probe transparency induced by quantum interference in a Vee-type atom consisting of an excited doublet coupled to a single ground level by the vacuum. We show that the amplitudes of the quantum-beat oscillations are greatly reduced, and the narrow resonances are substantially suppressed and broadened, for even very small dephasing rates and Doppler Broadening. Fluorescence quenching and the previously reported probe transparency can never occur in the presence of dephasing collisions and Doppler Broadening.
Fernando De C. Da Silva - One of the best experts on this subject based on the ideXlab platform.
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Solution of the Doppler Broadening function based on the fourier cosine transform
Annals of Nuclear Energy, 2008Co-Authors: Alessandro C. Gonçalves, Aquilino Senra Martinez, Fernando De C. Da SilvaAbstract:This paper provides a new integral representation for the Doppler Broadening function ψ(ξ, x), which is interpreted as being a Fourier cosine transform. This integral form allows the obtaining of an analytical solution in a simple and accurate functional manner as regards the elementary functions. The solution obtained through the new integral representation can be widely used in several applications such as the calculation of self-shielding factors and measurement corrections for the microscopic cross section through the activation technique.
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the derivation of the Doppler Broadening function using frobenius method
Journal of Nuclear Science and Technology, 2006Co-Authors: Daniel A.p. Palma, Aquilino Senra Martinez, Fernando De C. Da SilvaAbstract:An analytical approximation of the Doppler Broadening function ψ(ξ,x) is proposed. This approximation is based on the solution of the differential equation for ψ(ξ,x) using the methods of Frobenius and parameters variation. The analytical form derived for ψ(ξ,x) in terms of elementary functions is very simple and precise. It can be useful for applications related to the treatment of nuclear resonances, mainly for calculations of multigroup parameters and resonances self-protection factors, the latter being used to correct microscopic cross section measurements by the activation technique.
C. S. Lee - One of the best experts on this subject based on the ideXlab platform.
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Studies on sensitivity, resolution, and Doppler Broadening in gamma-ray imaging with pixellated semiconductor detectors
Nuclear Physics A, 2004Co-Authors: Ju Hahn Lee, C. S. LeeAbstract:We studied the Doppler Broadening effect which is one of the major issues pertaining to overall imaging quality in Compton cameras. For the study of Doppler Broadening due to the pre-collision electron momentum, we used a collimated beam of 662-keV gamma rays and selected events corresponding to the 90° Compton scattering using a Compton spectrometer, consisting of a 25-fold segmented germanium detector and a coaxial germanium detector shielded with a bismuth germanate (BGO) scintillator. Comparison of the energy spread due to Doppler Broadening between a silicon and a germanium detector was made with the Monte Carlo simulation. To see the effect of Doppler Broadening on the image resolution, we performed the Monte Carlo simulation in a simple backprojection method.
Aquilino Senra Martinez - One of the best experts on this subject based on the ideXlab platform.
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New analytical formulations for the Doppler Broadening function and interference term based on Kaniadakis distributions
Annals of Nuclear Energy, 2020Co-Authors: Willian Vieira De Abreu, Alessandro C. Gonçalves, Aquilino Senra MartinezAbstract:Abstract In thermal nuclear reactors, the calculation of the Doppler Broadening function and interference term are necessary for the precise determination of cross-sections. These functions are calculated numerically in systems for the calculation of macro-group parameters, which are necessary to know the power distribution of a nuclear reactor. Most of these calculations consider the standard model of Maxwell-Boltzmann statistics. More recently, some works proposed numerical and analytical solutions for the Doppler Broadening function using quasi-Maxwellian distributions. In this work, new analytical formulations are proposed for the Doppler Broadening function and interference terms. With these new approximations, the scattering cross-section was calculated. The results obtained show that the proposed approximations have good accuracy, with values of percentage deviation above 1% in regions near the resonance peak. For the values far from the peak, the new approximation presented better results when compared with previous analytical solutions.
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Analytical solution for the Doppler Broadening function using the Kaniadakis distribution
Annals of Nuclear Energy, 2019Co-Authors: Willian Vieira De Abreu, Alessandro C. Gonçalves, Aquilino Senra MartinezAbstract:Abstract Several works have been done for the development of models that generalize the Maxwell-Boltzmann distribution, aimed at encompassing physical phenomena that lie outside the thermal equilibrium. Amongst these, there are distributions that result from the non-extensive statistics of Tsallis and Kaniadakis. Starting from these generalized distributions, a Doppler Broadening function was proposed in recent papers, using the deformed Kaniadakis distribution, which was numerical, evaluated with the use of a Gauss-Legendre quadrature. From this perspective, this paper presents an analytical solution for the generalized Doppler Broadening function through obtaining a partial differential equation, considering the Kaniadakis distribution. This equation is solved analytically using the methods of Frobenius and variation of parameters, in order to obtain a generalized solution for the Doppler Broadening function, containing a deformation parameter κ , that measures the deviation in relation to the Maxwell-Boltzmann distribution. Finally, the results were produced considering several values for κ , with the intent of making a comparison with the reference values. For the validation of the deformed Doppler Broadening function’s analytical solution, a numerical solution of the partial differential equation was generated. It was possible to use this numerical solution as a benchmark for the analytical solution that was derived. It was demonstrated that the analytical solution obtained is consistent, because when κ tends to zero, the solution falls in the conventional form, when the Maxwell-Boltzmann distribution is considered. Apart from this, the results were shown to be good, especially when we consider the temperature and power ranges for practical applications, as the maximum error obtained was smaller than 1%.
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A new formulation for the Doppler Broadening function relaxing the approximations of Beth–Plackzec
Annals of Nuclear Energy, 2016Co-Authors: Daniel A.p. Palma, Alessandro C. Gonçalves, Aquilino Senra Martinez, Amir Zacarias MesquitaAbstract:Abstract In all nuclear reactors some neutrons can be absorbed in the resonance region and, in the design of these reactors, an accurate treatment of the resonant absorptions is essential. Apart from that, the resonant absorption varies with fuel temperature due to the Doppler Broadening of the resonances. The thermal agitation movement in the reactor core is adequately represented in the microscopic cross-section of the neutron-core interaction through the Doppler Broadening function. This function is calculated numerically in modern systems for the calculation of macro-group constants, necessary to determine the power distribution of a nuclear reactor. It can also be applied to the calculation of self-shielding factors to correct the measurements of the microscopic cross-sections through the activation technique and used for the approximate calculations of the resonance integrals in heterogeneous fuel cells. In these types of application we can point at the need to develop precise analytical approximations for the Doppler Broadening function to be used in the calculation codes that calculate the values of this function. However, the Doppler Broadening function is based on a series of approximations proposed by Beth–Plackzec. In this work a relaxation of these approximations is proposed, generating an additional term in the form of an integral. Analytical solutions of this additional term are discussed. The results obtained show that the new term is important for high temperatures.
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New Methods in Doppler Broadening Function Calculation
Current Research in Nuclear Reactor Technology in Brazil and Worldwide, 2013Co-Authors: Daniel A.p. Palma, Alessandro C. Gonçalves, Aquilino Senra Martinez, Amir Zacarias MesquitaAbstract:In all nuclear reactors some neutrons can be absorbed in the resonance region and, in the design of these reactors, an accurate treatment of the resonant absorptions is essential. Apart from that, the resonant absorption varies with fuel temperature, due to the Doppler broad‐ ening of the resonances (Stacey, 2001). The thermal agitation movement of the reactor core is adequately represented in microscopic cross-section of the neutron-core interaction through the Doppler Broadening function. This function is calculated numerically in modern sys‐ tems for the calculation of macro-group constants, necessary to determine the power distri‐ bution in a nuclear reactor. This function has also been used for the approximate calculations of the resonance integrals in heterogeneous fuel cells (Campos and Martinez, 1989). It can also be applied to the calculation of self-shielding factors to correct the meas‐ urements of the microscopic cross-sections through the activation technique (Shcherbakov and Harada, 2002). In these types of application we can point out the need to develop pre‐ cise analytical approximations for the Doppler Broadening function to be used in the codes that calculates the values of this function. Tables generated from such codes are not conven‐ ient for some applications and experimental data processing.
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Solution of the Doppler Broadening function based on the fourier cosine transform
Annals of Nuclear Energy, 2008Co-Authors: Alessandro C. Gonçalves, Aquilino Senra Martinez, Fernando De C. Da SilvaAbstract:This paper provides a new integral representation for the Doppler Broadening function ψ(ξ, x), which is interpreted as being a Fourier cosine transform. This integral form allows the obtaining of an analytical solution in a simple and accurate functional manner as regards the elementary functions. The solution obtained through the new integral representation can be widely used in several applications such as the calculation of self-shielding factors and measurement corrections for the microscopic cross section through the activation technique.
Vladimir M. Shalaev - One of the best experts on this subject based on the ideXlab platform.
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Elimination of Doppler Broadening at coherently driven quantum transitions
Physical Review A, 1999Co-Authors: Alexander Popov, Vladimir M. ShalaevAbstract:Possibilities of elimination of Doppler Broadening by making use of atomic coherence in ladder- and folded-type configurations of quantum transitions are considered. A simple physical analysis in terms of modification of the frequency-correlation factor for cascade and multiphoton processes in strong driving fields is developed.