Origins of radiation-induced attenuation in pure-silica-core and Ge-doped optical fibers under pulsed x-ray irradiation

We investigated the nature, optical properties, and decay kinetics of point defects causing large transient attenuation increase observed in silica-based optical fibers exposed to short duration and high-dose rate x-ray pulses. The transient radiation-induced attenuation (RIA) spectra of pure-silica-core (PSC), Ge-doped, F-doped, and Ge + F-doped optical fibers (OFs) were acquired after the ionizing pulse in the spectral range of [∼0.8-∼3.2] eV (∼1500-∼380 nm), from a few ms to several minutes after the pulse, at both room temperature (RT) and liquid nitrogen temperature (LNT). Comparing the fiber behavior at both temperatures better highlights the thermally unstable point defects contribution to the RIA. The transient RIA origin and decay kinetics are discussed on the basis of already-known defects absorbing in the investigated spectral range. These measurements reveal the importance of intrinsic metastable defects such as self-trapped holes (STHs), not only for PSC and F-doped fibers but also for germanosilicate optical fibers as clearly evidenced by our LNT measurements. Furthermore, our results show that fluorine co-doping seems to decrease the RIA related to the strain-assisted STHs absorption bands in both types of optical fibers. Regarding Ge-doped glasses, besides a description of the defects responsible of the RIA, highlighting the STHs' role in their transient response, we provide a clear correlation between the GeX and GeY centers' kinetics. In conclusion, the presented results improve our understanding of the transient RIA origin in the ultraviolet and visible domains. The lack of knowledge about the defects causing the RIA in the near-infrared domain will require future studies

Radiation Detection with Radiosensitive Pure-Silica Core Ultra-Low Loss Optical Fiber

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Performances of Radiation-Hardened Single-Ended Raman Distributed Temperature Sensors Using Commercially-Available Fibers

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Steady-State X-Ray Radiation-Induced Attenuation in Canonical Optical Fibers

The so-called canonical optical fibers (OFs) are samples especially designed to highlight the impact of some manufacturing process parameters on the radiation responses. Thanks to the results obtained on these samples, it is thus possible to define new procedures to better control the behaviors of OFs in radiation environments. In this article, we characterized the responses, under steady-state X-rays, of canonical samples representative of the most common fiber types differing by their core-dopants: pure silica, Ge, Al, and P. Their radiation-induced attenuation (RIA) spectra were measured online at both room temperature (RT) and liquid nitrogen temperature (LNT), in the energy range [0.6-3.0] eV (2100-410 nm), highlighting the RIA growth kinetics during the fiber exposure up to an accumulated dose of 200 Gy(SiO2) at a constant dose rate of 100 mGy/s at RT. At LNT, the deposited doses varied between 100 and 180 Gy, with a time-dependent dose rate. In order to understand the origin of the excess losses and the difference between the RIA spectral shapes observed at the two temperatures, spectral decomposition of the optical losses has been performed using a set of Gaussian absorption bands related to the already known point defects. As a result, if the RIA in the visible domain is quite well understood, the knowledge of the RIA origin in the near-IR remains incomplete, justifying new and deeper studies to clarify the response of the fibers under steady-state irradiation

Origins of radiation-induced attenuation in pure-silica-core and Ge-doped optical fibers under pulsed x-ray irradiation

International audienc

Ultra-high Dose Rate Pulsed X-ray Source Monitoring Based On Radioluminescent N-doped Optical Fiber

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