A novel ultraviolet (UV) optical fiber sensor (UVOFS) based on the scintillating material La2O2S:Eu has been designed, tested, and its performance compared with other scintillating materials and other conventional UV detectors. The UVOFS is based on PMMA (polymethyl methacrylate) optical fiber which includes a scintillating material. Scintillating materials provide a unique opportunity to measure UV light intensity even in the presence of strong electromagnetic interference. Five scintillating materials were compared in order to select the most appropriate one for the UVOFS. The characteristics of the sensor are reported, including a highly linear response to radiation intensity, reproducibility, temperature response, and response time (to pulsed light) based on emission from a UV source (UV fluorescence tube) centered on a wavelength of 308 nm. A direct comparison with the commercially available semiconductor-based UV sensor proves the UVOFS of this investigation shows superior performance in terms of accuracy, long-term reliability, response time and linearity.
The purpose of this article is to explore the cause of the over-response phenomenon of fiber x-ray sensor. The sensor is based on a length of PMMA fiber, whose end is filled with the scintillation material Gd2O2S:Tb. The Monte Carlo simulation software GEANT4 uses the phase space file provided by the International Atomic Energy Agency (IAEA), by irradiating the fiber x-ray sensor in the water phantom, counting the fluorescence signal of the optical fiber x-ray sensor after propagation through the fiber. In addition, the number of Cerenkov photons propagating through the fiber is also counted. Comparing this article with previous research, we believe that one of the reasons for the over-response of the fiber x-ray sensor is the non-linear response of the deposition energy of the scintillator to the fluorescence. By establishing a region of interest and counting the x-rays in this region, the simulation results show that the counted number of x-rays that may affect the fiber x-ray sensor is the biggest in the area of interest at a water depth of 5 cm. This result is close to the maximum dose point of the experimental and simulated percentage depth dose (PDD) curve of fiber x-ray sensor. Therefore, the second reason of the over-response phenomenon is believed to be fact that the inorganic materials such as Gd2O2S:Tb have larger effective atomic numbers, so the fiber x-ray sensors will cause more collisions with x-ray in a low energy region of 0.1 MeV–1.5 MeV.
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