Research Of Optical Path Coupling Simulation And Image Reconstruction Algorithm In Thermal Neutron Digital Radiography

While the interaction between Neutron (n) and materials, it will not directlyproduce ionization. It’s ray absorption law completely different from the X and specialqualities, so it has broad prospect of application in some Non-Destructive Testing fields,such as aviation, aerospace, machinery, petrochemical, materials, nuclear industry,medical and so on.Any energy of neutron beams can be used for neutron radiation imaging inprinciple. While Thermal Neutron has very favorable attenuation characteristics andimaging is intuitively and effectively, so that Thermal Neutron (neutron energy around0.05-0.5eV) Digital Radiography is widely used in Neutron Digital Radiography fields.Thermal Neutron Digital Radiography System is a complex system, involving Threeparts:1) Neutron Source. Including the neutron source, moderator structure, shieldinglayer To produce the neutron radiation beam for neutron imaging.2) Collimator.collimating and correcting the neutron beam frome the neutron source. Improvingparallelism and leading the neutron beam to objects. Collimator has direct influence onthe resolution of the images.3) Image detecting system (including neutron conversionscreen). Converting the neutron beam space distribution of sample information to theimage signals and recording that for the subsequent processing.Based on the Natural Science Foundation of China (Item Number:61171157), theproject researched a number of key issues of Thermal Neutron Digital RadiographySystem: Modeling and analyzing the coupling of ICCD for Low-Light-Level Imaging,analyzing the imaging quality, MTF and some other parameters of several couplingmodels, comparing the advantages and disadvantages of four different coupling models,all that based on ZEMAX which is an optical CAD software; Analyzing the influencedfactors of Neutron Computed Tomography projection data, mainly analyzing theproblems such as the beam hardening, scattered neutrons, the white spot noise ofgamma rays, interpolation of less projection data, and using pretreatment andaftertreatment methods to correct reconstruction in order to improve the imageresolution, and then comparing the images reconstruction results that with pretreatmentand aftertreatment and without; Using MATLAB to reconstruct the images and comparethe advantages and disadvantages of different reconstruction algorithms. On that basis,we present an Accelerated Algebraic Reconstruction Technique based on Newton-Raphson scheme, the algorithm can observably improve the speed whilekeeping the image quality.