Abstract

Radiation-induced attenuation (RIA) based dosimetry exploiting phosphosilicate optical fiber has been established as a reliable and precise dosimetry technique, up to at least 500 Gy(SiO₂), in particular in the infrared and visible domains. For lower doses, the larger radiation sensitivity coefficients of those fibers in the visible domain (ξ > 100 dB·km⁻¹·Gy⁻¹) than in the IR domain (ξ ∼ 4 dB·km⁻¹·Gy⁻¹) appear as more appealing. However, in radiation-rich locations the devices are hardly to manipulate and have to be replaced after a certain dose when the dynamic range of the interrogator is attained or when doses exceed 500 Gy. To overcome this issue, we investigate the feasibility to reset and re-use P-doped multimode fiber dosimeters operating in the visible domain through photobleaching. To achieve this purpose, we injected post-irradiation five different 4 mW lasers [1550 nm, 1060 nm, 640 nm, 514 nm and 403 nm] in an irradiated (5 Gy; 10 mGy/s) P-doped multimode OF to evaluate their potential to bleach the visible RIA. With the most efficient laser (403 nm), at least 80% of the visible range RIA is bleached in 2 hours. Successive re-irradiations of the same sample present the same RIA kinetics, confirming that the fiber calibration coefficients remain unaffected by the photobleaching process. Those results open the way to more advanced fiber dosimeter architectures with longer lifetime and higher achievable dose ranges.