在基于CCD相机的中子照相系统中,反射镜距离闪烁屏太近就会将部分荧光反射回闪烁屏,将闪烁屏照亮,入射中子束的少部分还会被反向散射回闪烁屏,形成图像本底叠加在图像上,对定量分析和CT重建结果产生影响。为此建立了反射镜所引入反射分量的计算方法,可根据闪烁屏受照分布和反射镜参数计算反射分量的分布,并对中子反向散射进行了蒙特卡罗模拟,计算结果与实验测量的本底分布规律相符。

In a CCD based neutron radiography system,some fluorescent light will be reflected back to the scintillator by the mirror if the mirror is too close to the scintillator. Some of the incoming neutrons may also be scattered back to the scintillator. These two factors form a strong background that cannot be neglected. This background is harmful to quantitative analysis and CT reconstruction. The analytic calculation of the reflection component as the well as Monte Carlo simulation of the back-scattering component has been carried out,the result of which agrees well with the background measurements. The background component introduced by mirror accounts for more than 10% of the whole background in a typical detection system configuration.