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Habilitation Thesis
DOI
10.11606/T.43.2014.tde-14102014-152032
Document
Author
Full name
Masao Matsuoka
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1992
Committee
Watanabe, Shigueo (President)
Donângelo, Raul José
Lejbman, Iuda Dawid Goldman Vel
Panepucci, Horacio Carlos
Yarschel, Alan Douglas
Title in Portuguese
PROPRIEDADES DOSIMÉTRICAS DO QUARTZO NATURAL BRASILEIRO E SUA APLICAÇAO NA GEOCRONOLOGIA GEOCRONOLOGIA
Keywords in Portuguese
Dosimetria
Física nuclear
Abstract in Portuguese
Foram investigados os sinais de termoluminescência (TL) e de ressonância de spin eletrônico (RSE) de grãos de quartzo extraídos de uma formação geológica brasileira. É confirmado que a curva de emissão termoluminescente acima da temperatura ambiente é composta de vários picos de emissão devidos a diferentes grupos de armadilhas, e que o espectro de emissão termoluminescente consiste de três bandas: duas observadas a temperaturas até 400°C e a terceira acima de 400°C. As duas primeiras bandas comportam-se diferentemente com o aumento da dose absorvida no quartzo irradiado pela radiação gama do Co: apresentam linearidade e supralinearidade; a terceira varia linearmente com a dose. A dose acumulada da radiação natural foi avaliada, observando-se o aumento da intensidade da emissão termoluminescente referente à terceira banda com a dose absorvida. Foram também estudadas à temperatura ambiente a forma e a dependência com a potência da microonda do sinal dos centros E\' 1 , usando um espectrômetro de RSE da banda-X. Mostra-se que a forma do sinal depende da dose absorvida, e que o produto dos tempos de relaxações spin-rede j spin-spin cresce com o aumento da dose absorvida até 8,5x10 Gy. Um estudo de tratamento térmico isocrônico indica uma correlagão entre a curva de emissão termoluminescente acima de 370 C e os centros E\'1. Através dos valores dos parâmetros que caracterizam o decaimento térmico do sinal de RSE dos centros E\' 1 , a meia-vida pode ser estimada à temperatura ambiente, permitindo a utilização dessa curva de emissão para datar o material estudado
Title in English
Dosimetrics PROPERTIES of the BRAZILIAN NATURAL QUARTZ AND ITS APPLICATION IN GEOCHRONOLOGY
Keywords in English
Dosimetry
Nuclear physics
Abstract in English
The thermoluminescence (TL) and electron spin resonance (ESR) signals of quartz grains extracted from a Brazilian geological formation have been investigated. It is confirmed that the TL glow curve observed above roem temperature is composed of various glow peaks due to different groups of traps, and that the TL emission spectra consist o f three bands: two observed at temperatures up to 400°C and the third above 400°C. The first two bands beha~e distinctly to the absorbed dose in quartz irradiated by 0co gamma rays: linearity and supralinearity, and the third presentes linearity. The accumulated dose of natural radiations is estimated by observing the enhancement of the TL emission intensity from the third band with the absorbed dose. The shape and microwave power dependence of the signal for E' 1 centers have been also studied at roem temperature using an X-band ERS spectrometer. It is shown that the signal shape depends on the absorbed dose, and that the product of spin-lattice and spin-spin relaxation time increases wi th increasing the absorbed dose up to 8. 5x10 Gy. An isochronal thermal anneal study indicates a certain correlation between the TL glow curve above 370°c and the E' 1 centers. From the derived values of the termal annealing parameters for the E' 1 centers, the half-life can be predicted for ambient temperature, and hence this TL glow curve should be stable enough to be used for dating this material.
 
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Publishing Date
2014-10-15
 
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