The effect of time and dose fractionation on the response of Harwell Gammachrome YR PMMA dosimeter

In some irradiation facilities, dosimeters may receive their total absorbed dose in two or more absorbed-dose increments. Some interruptions may be planned, for example multiple irradiations may be used to avoid increasing irradiation temperature in electron beam accelerators. Other interruptions may be the result of unplanned irradiator shutdowns. Dose fractionation effects from both planned and unplanned interruptions should be quantified by determining the effect for different dose fractions and interruption times between successive irradiations. This work describes experiments carried out on the response of Gammachrome YR PMMA dosimeters to both single fractions and fractionated doses (two absorbed-dose increments separated by different intervals of time: 0.5, 1, 2, and 24 h). Specific absorbance measurements were carried out as a function of post-irradiation time, following the completion of irradiation in the total doses, from 20 to 250 min. Our work demonstrates that specific absorbance as a function of post-irradiation time depends significantly on total dose and the fractionation time. For measurements taken 2 h after irradiation, it was found that relative response variations due to dose fractionation were between −3% and +2% for dosimeters irradiated to 0.2 kGy and from −1.34% to −4% for those irradiated to 2 kGy.