Nuclear Counter Effect of Silicon Photodiode Used in CsI(Tl)Crystal Calorimeter

We investigated the nuclear counter effect of the silicon photodiode mounted on a CsI(Tl) crystal detector due to the leakage of electromagnetic shower through the rear end of the crystal. Using electron beams at IHEP, we have tested its effect on the energy measurement by the CsI(Tl) calorimeter for BESIII experiment. The results are found to be in good agreement with that of GEANT simulation and the effect for the BESIII calorimeter is negligible.