Radiation damage of plastic scintillators

Degradation and annealing mechanisms in polystyrene were studied in order to account for the losses in transmittance and light yield observed in polystyrene-based plastic scintillators. Special emphasis was put on irradiations in oxygen and on the oxygen annealing process. These experiments indicated that: (a) irradiations in which oxygen was continuously available throughout the bulk of the polystyrene sample were the most damaging; (b) during the oxygen annealing process, the annealing rate was proportional to the oxygen diffusion rate; and (c) oxygen reacted with free radicals in the sample, contributing to an increase in permanent radiation-induced absorption