Development of fading correction method for a quantitative evaluation using Imaging Plates as an integral dosemeter

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An imaging plate (IP) made of BaFBr:Eu^<2+> phosphor has many advantages as a detector of two-dimensional images, and has been utilized in a number of fields. However, there are relatively few reports of applying IPs as an integral-type detector, because IPs have a large fading effect.The aim of this research is to determine functional equation for the fading correction by clarifying a characteristic of fading and develop a quantitative evaluation method.The results are listed below;1. By applying Arrhenius' equation to the experimental results, the fading effect is expressed as an equation having two variables: elapsed time(t) and temperature(K), as the sum of a few exponentially-decaying components. The activation energy, calculated from an equation, becomes higher as the component proceeds from 0.53 to 0.90 eV, indicating that fading occurs in the order of the component having the lower activation energy.2.The dependence of fading patterns of photo-stimulated luminescence (PSL) from IPs on alpha, beta, and gamma radiation and their energies is investigated. It is found that the fading effect is independent of the type and the energies of the incident beta and gamma rays except for the first component, which fades out very quickly after irradiation with alpha rays.3. A new method that eliminates the first short half-life component, which has a relatively low activation energy, has been developed by annealing an IP. The practical optimum condition for quantitative measurement is determined by using the fading correction equation.4.0n this condition, IPs are applied to a month integral dosemeter for gamma ray monitoring and its usefulness is evaluated.