Slow scintillation component and radiation induced readout noise in pure CsI crystals

Because of its fast decay time and low cost, pure CsI crystals are used in HEP experiments for fast crystal calorimetry. CsI crystal samples from three vendors were characterized for the Mu2e experiment at Fermilab with data used to define crystal specification. In addition to the fast scintillation component peaked at 310 nm, a slow scintillation component peaked at 450 nm with μs decay time was detected, which may be eliminated spectroscopically by using optical filters. It was also found that the slow scintillation component and the radiation induced readout noise in CsI crystals are highly correlated. The nature of the slow scintillation component is believed to be defects and/or impurity related.