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Doctoral Thesis
DOI
10.11606/T.43.1993.tde-04072012-143152
Document
Author
Full name
Airton Deppman
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1993
Supervisor
Committee
Herdade, Silvio Bruni (President)
Donangelo, Raul
Khouri, Marilia Tereza Freitas Cesar
Lima, Celso Luiz
Martins, Jader
Title in Portuguese
Estado dos mecanismos de fotoabsorçao do 238U na região das ressonâncias nucleônicas
Keywords in Portuguese
Fissão
Fotoabsorção
Propagação
Ressonâncias Nucleônicas
Sombreamento
Abstract in Portuguese
Medimos a seção de choque de fotofissão do 238U entre 200 e 1200 MeV, utilizando um feixe de fótons monocromáticos formados a partir da radiação de Bremsstrahlung dos elétrons armazenados no síncrotron Adone, em Frascati (Itália). Verificamos que para este núcleo, nesta faixa de energias, as seções de choque de fotofissâo e de fotoabsorção podem ser consideradas iguais, dentro dos erros experimentais. Comparando a seção de choque de fotoabsorção do urânio com a de outros núcleos, medidas também por nós em Frascati, verificamos que não há indícios do efeito de sombreamento até 1200 MeV. Por outro lado, comparando os nossos resultados com a seção de choque de fotoabsorção do próton na mesma faixa de energia, concluímos que as ressonâncias nucleônicas a energias superiores à da delta, notadamente as ressonâncias D13 e F15, são fortemente amortecidas nos núcleos complexos. Introduzimos um modelo fenomenológico a fim de descrever os nossos dados experimentais, obtendo resultados muito satisfatórios.
Title in English
State of the mechanisms of the photoabsorption of 238U in the region nucleonic resonances.
Keywords in English
Fission
Nucleonics resonances
Photoabsorption
Seeding
Shading
Abstract in English
We have measured the 238U photofission cross section between 200 and 1200 MeV using a Bremsstrahlung monochromatic photon beam in the Adone facilities, at Frascati (Italy). For this nucleus, we have verified that, at the energy range considered here, the photofission and photoabsorption cross sections can be considered as being identical. From the comparison of the uranium photoabsorption cross section with that one for other nuclei, also measured in Frascati, we verified that there is no evidence of the shadowing effect up to 1200 MeV. On the other hand, by comparing our results with the próton photoabsorption cross section in the same energy range, we concluded that there is an strong damping of the nucleonic resonances in the D13 and F15 region. We introduced a fenomenologic model to describe our experimental data, obtaining very satisfatory results.
 
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39900Deppman.pdf (3.27 Mbytes)
Publishing Date
2012-07-04
 
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