Cold Neutron Radiography Device Imaging System Simulation Analysis

Neutron radiography (NR) is an ascendant non-destructive testing technology. It is a valuable complementary of X andγrays radiography in the non-destructive detection of heavy metal subassembly and materials containing hydrogen. The cold neutron radiography (CNR) is an offshoot of NR. Because of the Bragg cutoff of the cross section while cold neutrons react to some crystalloid materials, the CNR has a great deal of excellences compared with NR techniques using other energy neutrons. Recent years, the CNR becomes to be a hot research technique around the world and develops rapidly.Generally, the CNR facility is composed of the cold neutron source, the collimation system and the imaging system. Due to the limit of the cold neutron source, there have not been CNR facilities inland yet. China Academy of Engineering Physics (CAEP) plans to found a CNR facility based their cold neutron source, and it is in the period of principium design. Up to now, simulation is the chiefly research method of CNR technique inland. However the spatial distribution of neutron beams penetrated through the sample was always considered as the image result of the simulation in the existing research. The influence to the image quality of the imaging system was ignored. This dissertation made a study of the simulation method of the imaging system which mainly consists of the converter, the mirror, the lens and the CCD camera.In the dissertation:the simulation model of the cold neutron converter is founded, the point spread function (PSF) of the converter is elicited, the influence to the image quality of the converter is analyzed, the calculation of the output light intensity distribution of the converter is realized; the simulation of the mirror, the lens, and the CCD camera is carried out, the finally image result of the CNR is completed; the simulation method of the imaging system which is set up in this dissertation is proved to be valid by the existed experimental data. According to the research result of this dissertation, the principium design parameters of the imaging system of the CNR facility in CAEP are put forward.The work of this dissertation promotes the development of the simulation research of the CNR technology. It provides a technical reference for the principium design of the CNR facility in CAEP. In the future, it will become an important technique means in the feasibility analysis of testing particular samples by the CNR technology.