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.