Dose response of natural-polymer-based gel dosimeter; Composition effects on white turbidity increase by irradiations

Yamashita, Shinichi; Hiroki, Akihiro; Nagasawa, Naotsugu; Murakami, Takeshi*; Taguchi, Mitsumasa

We developed a new polymer gel dosimeter. 2-Hydroxyethyl methacrylate (HEMA) and polyethylene glycol dimethacrylate (9G), which are less toxic than methacrylic acid or acrylamide, were used as constituents polymerizing after irradiations. A cellulose derivative, hydroxypropyl cellulose (HPC), was selected and crosslinked to form gel matrix by an irradiation of 2-MeV electron beam, which doesn't soften at higher temperature. Hydrogel of HPC is enough transparent to observe light scattering and absorption of products of radiation-induced polymerization. As a result of Co -ray irradiation of a few Gy, white turbidity arisen inside the gel, detailed behavior of which depended on composition of constituent monomers. It appeared at rather lower dose and its increase saturated at around 10 Gy of -irradiation when 9G was predominant. In order to quantify the degree of white turbidity, haze measurement and UV-vis absorption spectrometry were conducted. In addition, white turbidity evolution was also confirmed after irradiations of therapeutic C ion beam of 135 MeV/u although degree of white turbidity was less clear than that observed after -irradiation.