Abstract
The radiation induced optical absorption in Perspex ` Red 400 ' manufactured by Imperial Chemical Industries Limited, has been investigated with reference to its use in the dosimetry of high doses of ionizing radiation. It is found that this Perspex can be divided into three distinct types, each having a particular dyestuff formulation. The type currently available commercially exhibits two peaks in the induced absorption spectrum, at 613 mμ and 394 mμ. The highest extinction coefficient is obtained by measuring at 394 mμ with a spectrophotometer, in which case the optical density change in 0·15 cm thick samples is a linear function of dose between 0·2 and 1·5 Mrad. A method has been developed which requires only a simple white light photometer with suitable optical filtration, with a reduction in sensitivity of not more than 50%.