We describe our R&D effort to develop potentially radiation-hard scintillating and wavelength shifting fibers by doping fused-silica with cerium. The cerium-doped optical fibers with different core structures and concentrations were exposed to gamma radiation ( 60 Co) at different dose rates up to 100 kGy. We evaluated the radiation-induced degradation in photoluminescence, optical transmission, and recovery phenomena in the wavelength range from 300 to 700 nm. We were able to model the experimental data based on second-order rate equations where the fit parameters that govern the damage profile were utilized to predict recovery. We also measured the influence of radiation on the numerical aperture. Finally, we offer some thoughts on the use of these types of fibers in particle and nuclear physics detectors.
Our main aim was to investigate variations in the refractive index of a solution during chemical reaction. The variation of refractive index was measured through the entire acid-base titration process, especially near the equivalence point. To determine the equivalence point, the conductivity of the solution and the refractive index were measured simultaneously. In this preliminary study, sodium hydroxide and hydrochloric acid were used as the base and the acid solution, respectively. To measure the refractive index variation, a fiber-optic refractive index sensor was designed. The fiber-optic probe was dipped into the solution and acted as a refractive index sensor according to Fresnel's fundamental reflection law. A conductometer, a lab-made fiber-optic refractive index sensor ensemble, and a lab-made optical drop counter were each connected to a computer via an analog digital converter and the data acquisition was performed with the LabVIEW program. The equivalence point was derived easily from the refractive index data for the sodium hydroxide solution with different molarities of hydrochloric acid. In our opinion, the measurement of the variation of the refractive index during this kind of chemical reaction is more sensitive than the conductometric measurement.
The refractive index nðk; T) is a basic optical property of materials. The refractive index and the thermo-optic coefficient (dn=dT) are significant parameters of liquids for optically controlled systems, such as the direct measurement of liquid solution concentrations and optical paths. In this study, the variation in the refractive index of water in the liquid phase with temperature was measured with our self-designed fiber optic-based refractive index sensor and dn=dT values were obtained with a full-width half-maximum method at wavelengths of 980, 1426, and 1550 nm, respectively. Water is the most abundant and life-critical substance in the world, and its optical properties pose challenging scientific problems that require knowledge of the refractive index to be resolved. The results indicate that the experimental refractive index values are compatible with both the theoretical and experimental data in the literature. We also tested the refraction index results with two theoretical models and obtained good agreement between the calculated and experimental values. The resolution of the fiber optic-based refractive index sensor was 10 À5 . Our designed sensor could measure the refractive index of liquids with temperature with accuracy.
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