Study On Detector Efficiency Of Scintillation Optical Fiber For Transmission Neutron Digital Imaging

Neutron transmission imaging is a kind of non-destructive testing technology. The recording materials of neutron imaging have gone through the processes of film imaging, scintillation screen imaging and scintillation fiber imaging. Especially, as the rapid development of optoelectronic information and computer image processing technologies, the digitalized low light level imaging system has replaced the film imaging and the technology of neutron transmission imaging has reached a new era. In order to obtaining the clear neutron digital imaging, improving the detector efficiency of neutron screen is one of the measures.This thesis deals with the new technology of neutron-photon transition of scintillation fiber, and constructs the scintillation fiber detector efficiency model of neutron source, samples and the scintillation fiber array, by Monte Carlo Method. The main research contents are that choosing C6H5(CH-CH2)n and (CH2-CH)nC6H5CH3 as the materials of scintillation fiber, changing the parameters which affect the detector efficiency of scintillation fiber, in different incident energy levels. By detecting the energy deposition values, and analyzing the reasons that the changing the energy deposition values, the thesis explores the method of improving the detector efficiency of scintillation fiber.The Geant4 Monte Carlo simulation tool is used in this thesis, by modeling the neutron source, samples and scintillation fibers. All the parameters, such as the source energies, types of samples, the thickness of samples, the diameter of scintillation fibers, fiber material and fiber length, could be adjusted. And the testing curves could be gained by Least Squared Fitting. In the condition that the neutron source energies are 0.001MeV, 0.01MeV, 0.1MeV and 1MeV, separately, dealing with the materials of C6H5(CH-CH2)n and (CH2-CH)nC6H5CH3, the detector efficiency trends are:①increasing along with the increasing of neutron energy;②increasing sharply along with the distance of source and sample, and becoming smooth, then decreasing;③decreasing sharply along with the distance of sample and scintillation fiber, and becoming smooth, then decreasing slowly;④decreasing markedly along with the sample thickness and the increase of atomic numbers.This thesis simulates the scintillation fiber detector efficiency in different incident energies by Monte Carlo Method, and deals with the model parameters. In this way, the physical-mathematical model that the possible factors could affect the neutron scintillation fiber detector efficiency is gained, which has the theoretical guidance significance of improving the capabilities for neutron-photon scintillating materials of neutron transmission digital imaging technology.