Suppression of Afterglow in Microcolumnar CsI:Tl by Codoping With Sm ^ : Recent Advances

• Published in: IEEE transactions on nuclear science Vol. 56; no. 3; pp. 565 - 569
• Main Authors: Nagarkar, V.V., Thacker, S.C., Gaysinskiy, V., Ovechkina, L.E., Miller, S.R., Cool, S., Brecher, C.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.06.2009; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Availability; Crystals; Electromagnetic wave absorption; High-resolution imaging; Hysteresis; Image sensors; Optical imaging; Scintillator characterization; scintillators; Sensor phenomena and characterization; Spatial resolution; X-ray imaging
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2009.2016198

Microcolumnar CsI:Tl remains a highly desirable sensor for digital X-ray imaging due to its superior spatial resolution, bright emission, high absorption efficiency, and ready availability. Despite such obvious advantages, two characteristic properties of CsI:Tl undermine their use in clinical and high speed imaging: a persistent afterglow in its scintillation decay, and a hysteresis effect that distorts the scintillation yield after exposure to high radiation doses. In our earlier work we have discovered that the addition of 0.05 to 0.5 mol percent of Sm 2+ to crystals of CsI:Tl suppresses their afterglow by a factor of up to 50, even when subjected to a very high exposure of 120 R. This additive also diminishes hysteresis by an order of magnitude, which is a major accomplishment. Consequently, our work is now focused on developing codoped micro- columnar CsI:Tl,Sm films that can potentially combine excellent properties of the current state-of-the-art CsI:Tl films with the reduced afterglow and hysteresis observed in codoped crystals. While our earlier attempts in CsI:Tl,Sm film fabrication, reported at the previous IEEE meeting, demonstrated obvious advantages of the approach, the recent work has succeeded in producing films that show improvement by at least a factor of 7 in afterglow and 150% in brightness compared to the standard CsI:Tl films. We report these important results in this paper, along with other recent advances in film growth and new imaging results.