Ultralow-concentration Sm codoping in CsI:Tl scintillator: A case of little things can make a big difference

• The effects of ultralow-concentration Sm codoping on the scintillation characteristics of CsI:Tl were investigated.
• Afterglow was dramatically lowered while maintaining the light yield and energy resolution values.
• Application in CT medical imaging is discussed.

CsI:Tl scintillators were hindered from computer tomography and high-speed imaging applications by a serious afterglow problem. In this study, the effects of ultralow-concentration Sm codoping on the scintillation characteristics of CsI:Tl were investigated. Pulsed X-ray excited afterglow after 50 ms in 0.005 mol% Sm-codoped CsI:Tl was lowered by over one order of magnitude in comparison with Sm-free one. The beneficial effects of ultralow-concentration Sm codoping also appeared to be maintaining the light yield and energy resolution. The light yield and energy resolution after 0.005 mol% Sm codoping were 71,700 ± 6000 photons/MeV and 6.9% at 662 keV, respectively.