石墨双晶单色器性能检验及应用

中子能量选择成像作为一种前沿中子成像技术，可实现传统白光中子照相技术无法实现的功能，如研究工程材料中的晶粒分布、应变/应力分布、织构测量和相变分析等。本文依托中国先进研究堆(CARR)上的中子成像测试平台，在国内首次研制了石墨双晶单色器，建立能量选择中子成像技术。飞行时间实验测试结果表明，该双晶石墨单色器在选择4×10^-10 m的中子时波长分辨率可达2.6%，优于3.0%的设计指标。虽然在冷源未开启的实验条件下该石墨双晶单色器产生了较多的次级中子，但基于现有条件开展的镍基高温合金的中子能量选择成像实验能清楚分辨特定取向微晶粒的形貌及分布。结果表明研制的石墨双晶单色器可在CARR上开展能量选择成像实验，随着未来CARR冷源的开启，次级中子数量降低，中子束流品质进一步提高，将开展高质量的中子能量选择成像实验。

Performance Test on Double-crystal Graphite Monochromator and Its Relative Application

Neutron energy selective imaging, a novel neutron radiography technology, is capable of being used in some fields of science and engineering beyond the conventional neutron radiography technology, such as the distributions of crystal granules and stress/strain, texture test and phase transition analysis in engineering materials. In virtue of the neutron radiography test platform located at China Advanced Research Reactor (CARR), the double-crystal graphite monochromator was designed and the neutron energy selective imaging technology was initially developed for the first time in China. The experimental results based on time-of-flight (TOF) method demonstrate that, for the selection of neutrons with a wavelength of 4×10^-10 m, the wavelength resolution of designed monochromator can achieve 2.6% (much higher than the target value of 3.0%). Many secondary neutrons were produced simultaneously by the monochromator on this experimental condition due to the lack of cold neutrons. However, the experiment on Ni-based high-temperature alloy was still carried out and the morphology and distribution of specific oriented-plane microcrystalline particles can be observed clearly. Thus the designed monochromator can meet the demand of neutron energy selective radiography experiment at CARR. And high-quality neutron energy selective radiography experiments can be effectively performed with reduced secondary neutrons and improved beam quality using cold neutrons in future.