GEANT4 simulation study of over-response phenomenon of fiber x-ray sensor

【摘要】 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 Gd₂ O₂ S: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 Gd₂ O₂ S: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.更多还原

【Abstract】 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 Gd₂ O₂ S: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 Gd₂ O₂ S: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.更多还原