Near-Infrared Light Attenuation Measurements of Radiophotoluminescence FD-7 Dosimeters Irradiated With X -Rays at High Doses

Dosimetry techniques at high dose levels in the kGy-MGy range are challenging and still insufficiently explored. One of the emerging candidates for high level applications is silver doped metaphosphate glass, commercially known as FD-7 radiophotoluminescence (RPL) dosimeters. In this study, a free-space optical setup is used to enable dedicated study for online (during irradiation) characterization of RPL dosimeters. Transmission spectra are measured online as a function of wavelength, dose and dose rates, with additional monitoring of post-irradiation recovery kinetics. The present work focuses on the near-infrared (NIR) analysis, comparing it with previous studies in the visible range and verify the feasibility of extending the detection range of FD-7 dosimeters to higher doses by probing it with longer wavelengths. For the first time, radiation-induced attenuation (RIA) has been reported in the NIR domain and with dose deposition up to 862 kGy. RIA shows monotonic increase with dose up to few kGys and a saturation trend is observed at higher doses. The sensitivity response is dependent on the wavelengths and aligns with the previous studies in the visible domain. Minor recovery is observed in RIA after the irradiation end. Additionally, dose rate effects on RIA kinetics is tested by changing the dose rates from 1.77 Gy/s down to 0.36 Gy/s.