Generalizações do fenômeno de alargamento doppler

• Ano de defesa: 2019
• Autor(a) principal: Almeida, Guilherme Guedes de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Rio de Janeiro; Brasil; Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia; Programa de Pós-Graduação em Engenharia Nuclear; UFRJ
• Palavras-chave em Português: Alargamento Doppler; Funções de Voigt; Aproximação de Bethe e Placzek; Distribuição quase-maxwellianas; Distribuição de Tsallis; Distribuição de Kaniadakis; CNPQ::ENGENHARIAS::ENGENHARIA NUCLEAR::TECNOLOGIA DOS REATORES
• Link de acesso: http://hdl.handle.net/11422/13289

The thermal nuclei motion in the reactor core is properly represented in the microscopic cross section of the neutron-nucleus interaction through the Doppler Broadening Function Ψ(x, ξ), as well as in the Interference Term Function X(x, ξ), whose functional forms are derived from Quantum Mechanics, through the single level Briet-Wigner formalism, and from Statistical Mechanics, with the MaxwellBoltzmann velocity distribution. The results thus obtained present in their functional forms, integrals without analytical solution and wich has complicated structure, making the use of some approximations useful. Then, we consider the Bethe and Placzek approximations to obtain approximate expressions for the original functions Ψ(x, ξ) ≈ ψ(x, ξ) and X(x, ξ) ≈ χ(x, ξ). The first type of generalization proposed in this thesis consists in not considering the Bethe and Placzek approximations. In this context, the effect of each one of these approximations, as well as their combinations in pairs, are studied individually. In this way, one can identify the most relevant approximations, as well as relate them to the physical concepts that justify them. The second proposal of generalization is to study the consequences of considering a deformed statistical velocity distribution in place of the Maxwell-Boltzmann distribution. It is considered, then, two quasiMaxwellian statistical distributions, namely the Tsallis statistics, dependent on a parameter q, and that for Kaniadakis, dependent on a parameter κ. Thus, keeping the way of understanding the Quantum Mechanics of the subject unchanged, two deformations in the gaussian behavior of the Maxwell-Boltzmann distribution are considered. The research carried out intends to extend the understanding of the Doppler Broadening Phenomenon by importing concepts from other areas of knowledge.