STABILITY OF RESPONSE OF RED PMMA DOSIMETERS AT DIFFERENT TEMPERATURES

Dosimetric response and post-irradiation stability of commercially ava ilable 2 mm thick polymethyl methacrylate sheets have been investigate d spectrophotometrically. The response curves at 615, 650 and 700 nm s how linear response from 4 to 15 kGy. At 640 nm the response is linear from 4 to 20 kGy and with proper calibration, the dosimeter can be us ed up to 50 kGy. The stability of response of red PMMA dosimeter durin g post-irradiation swage at different storage temperature (-10, 26,35, 40, 50-degrees-C) has also been investigated at 640 nn. The dosimeter s irradiated to 10 or 20 kGy and stored al room temperature show stabl e response for about three weeks, which is followed by slight and grad ual decrease in response. The response during post-irradiation storage at lower temperature (-10 to 35-degrees-C) is stable over a period of 15 days while at higher temperature (45 and 55-degrees-C), fading of colour takes place which is faster at higher temperatures. These resul ts show that the dosimetric characteristics of commercially available 2 mm thick red PMMA sheets are suitable for its possible application i n radiation processing, such as sterilization of medical supplies and food irradiation, however storage of dosimeters at temperatures above 35-degrees-C should be avoided.