Suppression Of Afterglow In CsI(Tl) By Codoping With Eu/sup 2+/: Fabrication Of Microcolumnar Films For High-Resolution High-Speed Imaging

Although CsI:Tl is one of the brightest and most efficient scintillator materials ever developed, its applicability for high speed imaging is limited by its persistent afterglow. We have demonstrated that much of this afterglow can be suppressed by the addition of Eu²⁺ to the CsI host lattice. The magnitude of the effect depends strongly on the duration of the excitation pulse, but is virtually independent of its intensity. Our observations indicate that the presence of Eu²⁺ ions introduces a set of electron traps that fundamentally alter the decay kinetics, making the material useful for such applications as high speed radiography and, perhaps, X-ray CT. At RMD several single crystals of CsI:Tl,Eu with Eu²⁺ concentrations between 0.05 to 0.5 mole percent have been grown using the Bridgman technique. Here we report on our fabrication of microcolumnar films of the material using thermal vapor deposition for high-resolution digital radiography applications. Our data suggests that the afterglow suppression effect has a profound impact on high speed imaging performance, allowing rapid data acquisition with substantially reduced persistence from previous frames. The latest results on the effect of the codopant on the luminescence from CsI:Tl crystals as well as microcolumnar films will be reported.