Comparative study of the dose rate influence in the radiochromic polymeric film dosimeter response

Abstract

Most of film dosimetry is based on optical signal measurements since the spectrophotometric technique is cheap and widespread. Radiation induced chemical reactions take place in the material creating and/or enhancing absorption bands in the visible and/or ultraviolet regions of the spectrum. The response of most films used in routine dosimetry is usually influenced by the environmental conditions (temperature, humidity, ligth), dose rate and post irradiation storage. Several film dosimeters are commercially available for the absorbed dose measurements, in this work the effects of dose rate changes in optical density (OD) of film dosimeters (polymethylmetacrylate – PMMA) and polycarbonate – PC) were investigated and compared. Polycarbonates has been investigated as a new dosimetric material for industrial radiation processing aiming low cost, easy handle, fast and accurate response. PMMA dosimeters has been used routinely in dosimetry. The dose rate (kGy h-1) may influence the dosimeter response and appropriate corrections are necessary. The dosimeters were irradiated with 60Co gamma-radiation at dose rate in the range 0.26 – 2.6 kGy h-1 and with electrons from accelerator with maximum energy of 1.5 MeV and dose rate between 4.19 and 33.59 kGy s-1 to absorbed doses of 5 and 15 kGy, respectively. The irradiated dosimeters were measured using Shimadzu UV-2101PC spectrophotometer. It can observed that the films shows moderate dose-rate dependence (about 10%) in the analised range.