Abstract
The absorption spectra of deep centers in an imaging plate (IP) made of BaFBr0:85I0:15:Eu2+ have been studied in the ultraviolet region. Electrons trapped in deep centers are considered to be the cause of unerasable and reappearing latent images in IPs over-irradiated with X-rays. Deep centers showed a dominant peak at around 320nm, followed by two small peaks at around 345 and 380nm.By utilizing deeply trapped electrons, we have attempted to extend the dynamic range of an IP. The IP was irradiated by 150-kV X-rays with doses from 8.07mGy to 80.7Gy. Reading out the latent image by the stimulation of Eu2+ luminescence with a 633-nm He–Ne laser light from a conventional Fuji reader showed a linear relationship with irradiated dose up to 0.8Gy, but then becoming non-linear. After fully erasing with visible light, unerasable latent images were read out using 635-nm semi-conductor laser light combined with a photon-counting detection system. The dose–response curve so obtained gave a further two orders of magnitude extending the dynamic range up to 80.7Gy. Comprehensive results indicate that electrons supplied from deep centers to the F centers provided the extended dynamic range after the F centers became saturated. Based on these facts, a model of the excitation of deeply trapped electrons and PSL processes is proposed.
Published Version
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