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@MastersThesis{Diniz:2016:HEPhNe,
               author = "Diniz, Gabriel Sousa",
                title = "High energy emissions from thunderstorms: HEETs, from photons to 
                         neutrons toward the ground",
               school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
                 year = "2016",
              address = "S{\~a}o Jos{\'e} dos Campos",
                month = "2016-03-04",
             keywords = "neutrons, photons, cross sections, Monte Carlo, n{\^e}utrons, 
                         f{\'o}tons, se{\c{c}}{\~o}es de choque.",
             abstract = "Thunderstorms are the starting point of several intense phenomena 
                         such as gamma rays and X rays, neutron, positron and electron 
                         emissions. The X rays and gamma rays have energies that may reach 
                         100 MeV. The neutron emissions may be created by energetic gamma 
                         ray photons interacting with the air via Giant Dipole Resonance, a 
                         photonuclear reaction, related to thunderstorms and lightning in a 
                         way that is not completely understood yet. In this work neutrons 
                         were assumed to be created by gamma ray photons in the energy 
                         range of 10-30 MeV emitted by leader discharges. Their production 
                         and propagation toward the ground were investigated using computer 
                         simulations. Cross sections data banks were analyzed to provide 
                         estimations on the neutrons creation probability. The analysis 
                         revealed that the probability per collision of a photonuclear 
                         occurs varies between 0 and 3.2\% through the energy range of 10 
                         and 30 MeV. The photons mean free path within this energy range 
                         was analyzed together with the atmospheric density profile showing 
                         that for photon source altitudes above 1 km, the photons with this 
                         energy pass through a sufficiently high number of mean free path 
                         to ensure a collision. The free software EGS5 was used to treat 
                         the photons and electrons motion through the atmosphere in the 
                         intent of analyze the spread of the beams, that were assumed to be 
                         monodirectional. The photon beam presented an aperture of 
                         2-6\$^{o}\$ \$\pm\$ 2\$^{o}\$ while the electron beam was 
                         broader showing an aperture of 11-13\$^{o}\$ \$\pm\$ 
                         3\$^{o}\$. Since EGS5 does not take into account neutron 
                         production and motion, the neutron analysis was done with the 
                         FLUKA software simulating a photon beam in different initial 
                         heights and estimating the photon and neutron ground detection. 
                         FLUKA simulations have shown that neutrons are distributed at the 
                         ground within a radius of 2 km away from the source axis. The 
                         neutrons reached ground with a rate of 10\$^{-4} 
                         \$-10\$^{-2}\$ neutrons per gamma, which agrees with the cross 
                         section analysis done upon the neutron production. The neutron 
                         number decrease was used to estimate an upper limit of 5 km for 
                         the altitude of a punctual photon source that is capable of 
                         generating ground detectable neutrons. RESUMO: Nuvens de 
                         tempestade s{\~a}o o in{\'{\i}}cio de v{\'a}rios 
                         fen{\^o}menos intensos como os raios gama e raios X, bem como de 
                         emiss{\~o}es de n{\^e}utrons, p{\'o}sitrons e el{\'e}trons. As 
                         emiss{\~o}es de raios X e raios gama possuem energias que 
                         alcan{\c{c}}am 100 MeV. As emiss{\~o}es de n{\^e}utrons podem 
                         ser criadas por intera{\c{c}}{\~o}es entre raios gamma com o ar 
                         atrav{\'e}s da Resson{\^a}ncia Gigante de Dipolo, uma 
                         rea{\c{c}}{\~a}o foto-nuclear, relacionadas com as nuvens de 
                         tempestade e com raios de um modo ainda n{\~a}o totalmente 
                         compreendido. Neste trabalho sup{\~o}e-se que os n{\^e}utrons 
                         s{\~a}o criados por f{\'o}tons de raios gamma com energia entre 
                         10-30 MeV emitidos durante a propaga{\c{c}}{\~a}o do 
                         l{\'{\i}}der negativo. A produ{\c{c}}{\~a}o e a 
                         propaga{\c{c}}{\~a}o pelo ar destes n{\^e}utrons foram 
                         investigadas utilizando simula{\c{c}}{\~o}es computacionais. 
                         Bancos de dados de se{\c{c}}{\~o}es de choque foram analisados 
                         para estimar a probabilidade por colis{\~a}o de uma 
                         rea{\c{c}}{\~a}o foto-nuclear acontecer. A an{\'a}lise revelou 
                         que essa probabilidade varia entre 0\% e 3.2\% para f{\'o}tons 
                         com energia entre 10 e 30 MeV. O livre caminho m{\'e}dio dos 
                         f{\'o}tons no intervalo de energia de 10-30 MeV foi analisado 
                         junto com o perfil de densidade atmosf{\'e}rica. A an{\'a}lise 
                         mostrou que para f{\'o}tons com altitude inicial acima de 1 km, 
                         eles passam por livres caminhos m{\'e}dios o suficiente para a 
                         probabilidade de ocorr{\^e}ncia de ao menos uma colis{\~a}o ser 
                         garantida. O software livre EGS5 baseado no m{\'e}todo Monte 
                         Carlo foi usado para tratar o movimento dos f{\'o}tons e 
                         el{\'e}trons pela atmosfera no intuito de estudar a difus{\~a}o 
                         de feixes monodirecionais dessas part{\'{\i}}culas. Foi 
                         observado que o feixe de f{\'o}tons possui uma abertura entre 
                         2-6\$^{o}\$ \$\pm\$ 2\$^{o}\$ enquanto o feixe de 
                         el{\'e}trons possui uma abertura de 11-13\$^{o}\$ \$\pm\$ 
                         3\$^{o}\$ . A an{\'a}lise de n{\^e}utrons foi feita com o 
                         software FLUKA simulando um feixe de f{\'o}tons em diferentes 
                         altitudes iniciais e estimando a detec{\c{c}}{\~a}o de 
                         f{\'o}tons e n{\^e}utrons no solo. As simula{\c{c}}{\~o}es do 
                         FLUKA mostraram que os n{\^e}utrons se distribuem no solo em uma 
                         dist{\^a}ncia radial da fonte de 2 km, chegando ao solo numa 
                         raz{\~a}o entre 10\$^{-4}\$ at{\'e} 10\$^{-2}\$ 
                         n{\^e}utrons/f{\'o}tons, o que concorda com a an{\'a}lise das 
                         se{\c{c}}{\~o}es de choque. A diminui{\c{c}}{\~a}o dos 
                         n{\^e}utrons detectados em solo permitiu a estimativa de uma 
                         altura limite de 5 km para uma fonte pontual de f{\'o}tons capaz 
                         de produzir n{\^e}utrons detect{\'a}veis em solo.",
            committee = "Alves, Maria Virginia (presidente) and Tavares, Fernanda de 
                         S{\~a}o Sabbas (orientadora) and Ebert, Ute Maria (orientadora) 
                         and Costa, Joaquim Eduardo Rezende and Federico, Claudio Antonio",
           copyholder = "SID/SCD",
         englishtitle = "Emiss{\~o}es de alta energia provindas de nuvens de tempestade. 
                         HEETs: de f{\'o}tons para n{\^e}utrons ao solo.",
             language = "en",
                pages = "127",
                  ibi = "8JMKD3MGP3W34P/3L56P52",
                  url = "http://urlib.net/rep/8JMKD3MGP3W34P/3L56P52",
           targetfile = "publicacao.pdf",
        urlaccessdate = "25 nov. 2020"
}


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