Gamma-radiation damage effects on plastic scintillators The effect of radiation damage on a number of different scintillating materials has been investigated by measuring the apparent maximum energy change represented by the shift in the beta-spectrum end-point obtained from 204Tl. The damage curves have been shown to be represented by the equation y = A(1 - e−Bx ) where y is the percentage apparent energy change, x is the radiation dose in Mrad, and A and B are constants. The form of the equation remains the same for varying dose rates and materials although the values of A and B alter. It would appear that, for the samples examined, over 60% of the measured damage is due to the production of colour in the plastic, the remainder of the damage being produced in the actual scintillating chemicals themselves.