Thin plastic radiochromic dye films as ionizing radiation dosimeters

Radiochromic dye films were fabricated by casting polyvinyl butyral (PVB) in weakly acidic solution with the leucocyanide of pararosaniline. Calibrated films of 10 to 25 μm thickness were useful over a response range of about 103 to 105 Gy, by applying spectrophotometric analysis at the wavelength of the maximum of the radiation-induced absorption band (550 nm). The effects of temperature, pressure, and humidity during curing of the films pointed to the need for carefully controlling these parameters. For casting films at the high altitude of Mexico City, the optimum conditions are 45 to 75% r.h. and 20 to 25 deg C for a drying period of 72 to 92 hours, when the solvent is a mixture of ethanol and 2-methoxy ethanol. The response of films fabricated in this way was compared with those of commercially available PVB and Nylon films. The effects of temperature, humidity, and period of storage on the response of these films were studied in the range from -5 to 60 deg C and from 11.8 to 96.6% r.h. for up to four months between irradiation and spectral analysis. The results are reported. (author)