Clear Perspex, made to a standard specification of the UK Panel on Gamma and Electron Irradiation, and known as Perspex H.X., has been assessed for use as a reference dosemeter for megarad doses of gamma and electron radiation by a group of laboratories in co-operation. The radiation-induced increase in optical density of the material was used as a measure of dose. Recommendations are made for the choice of wavelength for measurement. Calibration data for doses up to 5 megarads are included. Studies have been made on the reproducibility as a dosemeter, on the response of different batches of the material to the same dose, and on the post-irradiation fading of the induced optical density. Recommendations for handling the material to achieve full accuracy and reliability are made.
