Radiation hardness study of CsI(Tl) scintillation crystals for the Belle II calorimeter
The electromagnetic calorimeter of the Belle II detector contains CsI(Tl) crystals of 30 cm length which have been used at the Belle experiment. We measure the light output degradation of CsI(Tl) crystals exposed to uniformly distributed absorbed dose. Four Belle typical crystals with known scintillation characteristics are irradiated with photons at a total dose of about 35 krad. Results show acceptable radiation hardness for the Belle II experiment conditions where the accumulated dose in crystals could reach 10 krad.