Radiation stability of plastic scintillators and wave-length shifters

The radiation stability of plastic scintillators and wave-length shifters for the calorimeter of the ZEUS detector at HERA has been investigated by irradiating them with low energy protons and a Co γ-source. Changes in light yield and absorption length have been measured with a xenon flash lamp. Absorbed total doses were 0.1-25 kGy for dose rates of 0.03 up to 10 kGy/h. Different surrounding atmospheres have been applied. The scintillator SCSN-38 shows a strong decrease of the absorption length with a fast recovery in air to a low permanent damage. The permanent loss in light yield is 4% for a dose of 10 kGy. The WLS Y-7 and K-27 dissolved in PMMA have small permanent damages in air and strong ones in nitrogen where no recovery takes place. Dose rate effects have not been seen either for the SCI or for the WLS