Influence of radiation damage on the performance of a lead/scintillator calorimeter investigated with 1–6 GeV electrons

The influence of radiation damage on energy resolution, linearity and uniformity of an electromagnetic lead/scintillator calorimeter was studied experimentally with 1–6 GeV electrons. Plastic scintillators and wavelength shifter bars were irradiated uniformly with γ rays. Both were identical with those of the ZEUS uranium calorimeter. The attenuation length of the scintillators was determined from bench tests of single scintillator tiles and from beam tests of the whole calorimeter. After exposure to a dose of 10 kGy the attenuation length of the scintillators decreased by a factor of 2. The experimental results show that the irradiation of the nearly 2 m long wavelength shifter bars affects the calorimeter much more than the damage of the scintillators which were only 19 cm long. Damaged and undamaged sections of the calorimeter were scanned with a moving radioactive γ source (60Co). The results demonstrate that the 60Co monitor system is a very precise tool to detect radiation damage in a sampling calorimeter.