Online and offline Radiation-Induced Attenuation measurements on FD-7 radiophotoluminescence dosimeters irradiated at high X-ray doses

Radiophotoluminescence (RPL) FD-7 glass dosimeters find applications in low to high dose radiation environments. This work presents an experimental characterization of RPL glass dosimeter, irradiated with 100 kV X-ray tubes at room temperature at doses ranging from 1.3 kGy to 0.47 MGy, much higher of their common use range. In this study, a customized set-up has been developed, allowing the online investigation of the glass transmission changes with radiation, known as Radiation-Induced Attenuation (RIA), as well as the recovery and post-mortem characterizations up to 2 months after irradiation. Multi-wavelength analysis was performed, focusing on the range between 200 nm and 800 nm. At 700 nm and 800 nm, RIA increases progressively with dose up to about 5 kGy, and tends to approach saturation (2-3 dB/mm) for doses higher than 50 kGy. Higher attenuation is reported at lower wavelengths: 445-nm light transmission reduces to only about 1% of its initial value after 2 kGy. RIA recovery after irradiation was observed, up to 6% at 700 nm wavelength within 3 h from the irradiation conclusion and up to 26% 2 months after, especially at doses in the kGy range. Both online RIA and its recovery are highly dependent on the selected wavelength and on the total absorbed dose. This information is crucial for the extension of the use of these dosimeters up to high doses, complementary to the RPL signal, traditionally used alone for the determination of doses up to the Gy range.