We investigated the influence of modifying the voltage of an X-ray tube with a tungsten anode between 30 kV and 225 kV, and therefore its photon energy spectrum (up to 225 keV), on the Total Ionizing Dose deposited in a single-mode, phosphorus-doped optical fiber, already identified as a promising dosimeter. Simulation data, obtained using a toolchain combining SpekPy and Geant4 software, are compared to experimental results obtained on this radiosensitive optical fiber and demonstrate an increase of the deposited dose with operating voltage, at a factor of 4.5 between 30 kV and 225 kV, while keeping the same operating current of 20 mA. Analysis of simulation results shows that dose deposition in such optical fibers is mainly caused by the low-energy part of the spectrum, with 90% of the deposited energy originating from photons with an energy below 30 keV. Comparison between simulation and various experimental measurements indicates that phosphosilicate fibers are adapted for performing X-ray dosimetry at different voltages.

We investigated the performance under γ and X-rays of an optical-fiber-based distributed dosimeter consisting of an embedded Optical Time-Domain Reflectometry (OTDR) interrogator operating at 1610 nm and a phosphorus-doped, single-mode, size-reduced optical fiber. Results show a linear response from 10 ^-3 to 10 ² Gy(SiO ₂ ), a proper functioning of the interrogator at least up to doses of 80 Gy(SiO ₂ ) and performances comparable to standard-sized distributed dosimetry systems found in literature.

We investigated the influence of the ambient light on the Radiation-Induced Attenuation (RIA) of Ge-doped optical fibers measured at the telecommunication wavelengths when exposed to a ⁶⁰ Co source, and in the visible and Near-InfraRed (NIR) domains when exposed to X-rays. From our results, it is possible to observe that this class of optical fibers are sensitive to the ambient light. Indeed, in all cases, their RIA value changes depending on the illumination conditions. In particular, the γ-ray irradiations revealed jumps in the measured RIA when changing the lamp of the irradiation chamber, whereas the X-ray irradiations reported that the relative photobleaching effect caused by the ambient light increases with the wavelength, up to ~1300 nm. The spectral study revealed no direct correlation between the absorption bands of the known Ge-related point defects and the external photobleaching phenomenon.

The radioluminescence response under X-rays is investigated for five different types of multimode silica-based optical fibers doped with Ge, P, Al, F or Ce. The results indicate that all tested fibers show a measurable radioluminescence signal at dose rates from 0.1 to 15 Gy(SiO2)/s, using 10-cm-long samples and a photomultiplier-based acquisition chain. Other influences of radiation, such as radiation-induced attenuation, are discussed in order to evaluate the potential of such fiber types for radiation detection or dosimetry applications.

We present a simulation-assisted methodology for the design of point or distributed fiber dosimeters exploiting the linear dependence of the infrared radiation-induced attenuation of a single-mode phosphosilicate optical fiber. We demonstrate by comparing Monte Carlo simulations and experiments at different irradiation facilities (X-rays, γ-rays, protons and atmospheric neutrons) that the sensitivity coefficient of this fiber is independent on the nature of particles and on dose rate, at least up to total ionizing doses in the order of 500 Gy. Our simulations allow us to simulate the dose deposited in the fiber core (and then the Radiation Induced Attenuation (RIA) levels) for the different classes of particles (photons, electrons, neutrons, protons and heavy ions) and for different energy ranges. From this data, and knowing the environments of targeted applications for the fiber optic dosimeters, we can discuss the different designs and achievable performance using this fiber. Examples are discussed with space applications, atmospheric balloon experiments and fusion-devoted facilities.

We characterized the radiation response in the visible domain of a new multimode graded-index phosphosilicate optical fiber (GIMMF), exposed to the harsh environment (pulses of 14 MeV neutrons, X-rays, γ-rays) associated with laser experiments at the OMEGA facility. The growth of permanent radiation-induced attenuation (RIA) was measured in situ after a series of laser shots involving a large production of 14 MeV neutrons (yields > 10 ¹⁴ n per shot). RIA linearly increases with accumulated neutron fluence without recovery between shots. The obtained results allow a precise evaluation of this GIMMF vulnerability when implemented as part of laser or plasma diagnostics. Our work also reveals the potential of this class of optical fiber to serve as a radiation monitor in the radiation-rich mixed environments of Megajoule class laser facilities, and to provide very fast and online estimation of the accumulated deposited dose at various locations of their experimental halls. In our experimental test configuration at OMEGA, 14 MeV neutrons are estimated to contribute to about 55% of the total deposited dose on the fibers, the other optical losses being related to X-ray and γ-ray contributions. Those measurements could be, for example, benchmarked to the radiation maps obtained by Monte Carlo simulation tools, potentially facilitating the evaluation of the ageing of diagnostics, components and systems as well as their maintenance operations.