会議発表用資料 Complementary approach for radiation dosimetry with Ag+-activated phosphate glasses

Kodaira, Satoshi  ,  Yanagida, Yuka  ,  Koguchi, Yasuhiro  ,  Kitamura, Hisashi  ,  Kawashima, Hajime  ,  Kurano, Mieko  ,  Ogura, Koichi

2016-07-08
内容記述
The use of Ag+-activated phosphate glass (hereafter, Ag-glass) as a personal dosimeter, based on radio photo luminescence (RPL) detection, is well-known [1]. An intense luminescence, which is proportional to the amount of the dose of the ionizing radiation, is emitted by excitation with ultraviolet light. The RPL signal covers dose measurement range with linearity from 10 μGy to 10 Gy so that the company provides personal dosimetry service.This work dedicates to the new approach of radiation dosimetry with Ag-glass for various radiation fields. The Ag-glasses provide three different signals of 1) radio photo luminescence (RPL), 2) nuclear etched-track and 3) optical absorption at specific peak. We present a complementary approach for radiation dosimetry with three different signals from the Ag-glass.The Ag+-activated phosphate glass (51.2wt%O, 31.6wt%P, 11.0wt%Na, 6.1wt%Al, 0.2wt%Ag) with size of 8.5 mm x 8.5mm x 1.5mm, AGC Techno Glass Co. Ltd., Japan, was employed. The Ag-glasses were irradiated to heavy ions from proton to xenon with energies of137Cs source, covering the dose range of 0.5 - 2 kGy.The dose due to RPL signals were obtained under the protocol of personal dosimetry service at Chiyoda Technol Corporation. The irradiated glasses were then etched in 7N NaOH solution with 70 degC. The produced etch pit was measured and analyzed with high speed microscope (HSP-1000, Seiko Precision Inc.). On the other hand, the optical absorption of stained glass due to the high dose γ-ray irradiation was measured with the spectrophotometer (U-3900H, Hitachi).The luminescence efficiency relative to gamma-ray dose was nearly constant for low LET particles with 10 keV/μm. For quite high LET particles of MeV/μm, such as Xe ions, the absorbed dose obtained from RPL underestimates 70% for calibrated ionization chamber result as shown in Fig. 1.We found out that the Ag-glass can be operated as nuclear etched track detector in our previous work [2]. This means that we can observe not only RPL but also nuclear etched tracks as well in the same glass material. The Ag-glass irradiated to Xe ions was etched and detected nuclear etched tracks after the RPL measurement. The dose obtained from LET spectrum of nuclear etched tracks agreed well with ionization chamber results at very high LET region of >1 MeV/μm, whereas RPL signals were underestimated for high LET particles as shown in Fig. 1.The Ag-glass was stained due to high dose gamma-ray irradiation. The strong absorption of 315 nm was observed in the glass irradiated to 0.5 - 2 kGy gamma-rays as shown in Fig. 2. Its absorbance corresponding to the colored concentration linearly depends on the dose, while the conventional RPL signal is to be saturated. This work dedicated to the new approach of radiation dosimetry with silver-activated phosphate glasses for various radiation fields. We found that the Ag-glasses provide independently three different signals of RPL, Nuclear etched-track and Optical absorption. The combination of thesethree signals allows us to widen the dynamic range of measuring dose (from 10 μGy to 2 kGy) and LET (linear energy transfer) (1 MeV/μm). For heavy ion dosimetry, the nuclear track detection will supply alternative signals in the glass dosimeter, which will be applicable for the dosimetry in the mixed radiation field. The optical absorbance measurement will allow to estimate dose in high dose environment such as inside the nuclear power plant and reactor decommissioning for Fukushima accident. Thus complementary approach for radiation dosimetry by combining three different signals from the Ag-glass will be applicable in various radiation fields.
「18th International Conference on Solid State Dosimetry」における口頭発表

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