[20a-G203-1~11] 16.1 Fundamental properties, evaluation, process and devices in disordered materials

[20a-G203-11] The dose response and mechanism of radiophotoluminescence phenomenon induced in Cu-doped glasses

〇(M1)Ryo Hashikawa¹, Yasuhiro Fujii¹, Atsushi Kinomura², Takeshi Saito², Arifumi Okada¹, Takashi Wakasugi¹, Kohei Kadono¹ (1.Kyoto Inst. Tech., 2.KURRI)

Keywords:dosimeter, copper, radiophotoluminescence

Radiophotoluminescence (RPL) is a luminescence phenomenon caused by the generation of new luminescent centers by radiation, and it is well known that RPL is observed in the Ag-activated phosphate glass. Since the emission intensity is proportional to the exposure dose, the Ag-activated phosphate glass has been applied for practical use as fluorescent glass for individual exposure dosimeters. However, there are few reports on RPL phenomenon other than Ag-activated phosphate glass, and its knowledge is not sufficient. Therefore, in our laboratory, we focused on Cu belonging to the same family as Ag and have explored new materials showing new RPL phenomenon. Raw material powders (NaNO₃, Al₂O₃, SiO₂, B₂O₃, CuO) were mixed in a mortar to obtain a desired composition, then melted in a platinum crucible at 1600°C for 2 h. After the glass melt was poured out onto the carbon plate, it was annealed for 1 h at a temperature around T_g. The produced glass was cut into a thickness of about 1 mm and optically polished. The composition of the produced glass is an aluminoborosilicate glass (25Na₂O·25Al₂O₃·10B₂O₃·40SiO₂ (mol%), hereinafter ABS25) doped with 0.005 mol% CuO. Gamma rays (⁶⁰Co) were irradiated to the glass samples at various doses. The irradiation was carried out with a ⁶⁰Co gamma ray irradiation apparatus at Research Reactor Institute, Kyoto University. Absorption and emission spectra were measured before and after irradiation. As a result, as the absorbed dose increased, the luminescence intensity near 2.5 eV (500 nm) attributed to Cu⁺ increased. Furthermore, a linear relationship was obtained in the range from 40 to 1.1 × 10³ Gy. There was a tendency to deviate to upper side from the straight line in the region with a small absorbed dose (40 Gy or less), and lower side from the straight line in the region with large absorbed dose (1.1 × 10³ Gy or more). In the region where the absorbed dose is small, the amount of generated defects is small, thus it is considered that the reaction suppressing the generation of Cu⁺ is predominant and the deviation from the straight line occurs. In the region where the absorbed dose is large, it is considered that the electron trapping reaction by Cu²⁺ reaches nearly saturated state and the integrated intensity becomes lower than the straight line.