反应堆中子边缘增强效应成像初步研究

中子边缘增强效应是近年来发展的基于中子波动性的新型中子成像技术.相较于传统的中子照相技术利用样品中不同元素对中子衰减能力的差别来得到样品内部的结构潜像,边缘增强效应成像利用中子射线穿过物体时各种元素对中子的折射率不同来反映物体的内部结构.为研究中子边缘增强效应成像的实际工业应用可行性,通过数值模拟方法分析了边缘增强效应的产生过程,并基于反应堆进行了不同条件下的多色热中子边缘增强效应成像实验.模拟与实验结果表明在适当准直比条件下,铝材料边缘将出现明显的边缘增强效应,该效应与准直比、样品与转换屏之间的距离密切相关.

Preliminary study on the neutron edge enhancement imaging at a reactor source

Neutron edge enhancement image is a recently developmental technique which is based not only on the amplitude like in the projection imaging but also on the contribution of phase alteration of the neutron beam. With the additional contrast from the difference of neutron refraction index in the sample which mainly leads to edge enhancement, this method can show more details about the neutron phase materials, especially some low attenuation contrast materials. Numerical simulation of neutron edge enhancement imaging is processed by MATLAB based on reflection theory and some experiments are carried out at a reactor using polychromatic thermal neutron beam line. The simulation and experiment results all show that a proper L/D condition would cause image enhancement at the edge of aluminum materials and the monochromatic neutron source isn＇t needed. The effect is related to L/D and the distance between sample and scintillator.