Regensburg 2007 – wissenschaftliches Programm
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ST: Fachverband Strahlen- und Medizinphysik
ST 2: Medizinphysik-Poster
ST 2.3: Poster
Montag, 26. März 2007, 12:30–13:30, Poster D
Investigation of afterglow mechanisms in the x-ray scintillator CsI:Tl+ — •Oliver Karg1, Jörg Zimmermann1, Heinz von Seggern1, Manfred Fuchs2, and Peter Schardt2 — 1Institute of Materials Science, Electronic Materials Division, Petersenstrasse 23, 64287 Darmstadt, Germany — 2Siemens AG, Medical Solutions, Vacuum Technology, Günther-Scharowsky-Strasse 1, 91058 Erlangen, Germany
The x-ray scintillator CsI:Tl+ has been studied extensively for many years. For medical applications needle like layers on a substrate coupled with a CCD-camera are utilized. The advantages of such needle shaped CsI:Tl+ layers are the high light yield and the spatial resolution due to the light guiding needles. For future medical instrumentation like fast computer tomography scintillators with a short lifetime are required. For this application the afterglow of present CsI:Tl+ is not satisfactory exhibiting a weak afterglow with lifetimes in the range of seconds. The present work provides some results on the understanding of the mechanism leading to the afterglow. With x-ray and UV excited spectral resolved time dependent measurements the contributions of the different transitions in both the short time and long time regime are analyzed. Several electronic transitions in the Tl+-ion and excitonic recombination are shown to be responsible for the fast luminescence. Defects responsible for the long term afterglow are investigated by means of thermally stimulated luminescence (TSL) techniques of x-ray irradiated CsI:Tl+. Detrapping and retrapping mechanisms are reported from samples treated in different atmospheres.