Development of real-time measurement system for emission and absorption of visible light during heavy gamma-ray irradiation

A system for the real-time measurement of the visible light emission from and absorption by a material in an intense gamma-ray field was developed. A white light-emitting diode produces a visible light beam that passes through an irradiated specimen and is measured by an ultraviolet–visible spectrophotometer through a long glass optical fiber accompanied with a Pb shielding configuration. A video camera provides real-time visual observation of the gradual change in the color state of the irradiated specimens. In order to study the formation of silver nanoparticles in detail, blue color dye was added to the radiolytic medium and its color change was examined as a function of irradiation dose to observe the interaction among radiation-introduced radicals in water, generated silver nanoparticles, and dye molecules. A mutual impact between the formation of silver nanoparticles and the deformation of the dye during gamma radiolysis are experimentally clarified. The combination of direct visual observation and optical absorption measurement is expected to provide powerful clues for elucidating various phenomena caused by irradiation effects.