γ-ray dosimetry using pararosaniline cyanide in dimethyl sulfoxide solutions

Abstract

A chemical radiochromic dosimeter using pararosaniline cyanide in dimethyl sulfoxide can be used over a wide absorbed dose range. Experiments show that the dosimeter has a main optical absorption maximum at 554 nm, which is 5 nm higher than that of other polar solvents. Millimolar solutions of leucodye containing small amounts of carboxylic acid or nitrobenzene show a linear response for absorbed doses up to 11.75 kGy. The yield of dye is linear with concentration up to 5 mM. At that concentration the upper limit of linear response range can be extended to about 40 kGy. The lower dose limit for 50 mM concentration of the dye precursor hexahydroxyethyl pararosaniline ( λ max=608 nm) is about 3 Gy, with ±5%SD at 95% confidence level, when using a 5 cm pathlength cell. Dye formation yield varies not only with concentration of the leucocyanide, but also with type of oxidizing agent and temperature during irradiation. The latter parameter is especially critical, as dimethyl sulfoxide freezes at 17°C. The effect of storage temperature on the color produced after irradiation at different dose levels was also studied.