基于小型加速器中子源的快中子层析实验研究

Experimental study of fast neutron tomography based on an compact accelerator neutron source

利用快中子穿透能力强的特点实现层析成像,对于大尺寸的无损检测具有重要意义。但快中子探测效率低,非期望信号引起图像噪声大,原始投影图像信噪比相对较低,实现快中子层析成像难度较大。本文利用中国工程物理研究院核物理与化学研究所研制的小型中子成像检测仪,获取了轻重材料混杂件不同角度下的快中子成像投影图像,通过对投影图像进行预处理提高图像信噪比,并采用迭代重建算法对投影图像进行重建,成功获取了模拟样件的三维结构分布,具备了内部轻材料孔洞缺陷的检出能力,表明采用小型加速器中子源可以实现快中子计算机断层扫描(Computed Tomography,CT)成像。

[Background]With the strong penetrability of fast neutrons, it is significant to use computed tomography (CT) neutron imaging to perform non-injury detection of large size samples. Fast neutron tomography is seldom performed because of the low efficiency of fast neutron detection and low signal to noise ratio of raw projected fast neutron image.[Purpose] This study aims to fulfill non-injury detection of some big size samples by using fast neutron tomography technology.[Methods] First of all, based on a pre-developed compact accelerator neutron source, a fast neutron tomography system was established. Then the raw projections of light and heavy material mixture sample from different angles were obtained. Fast neutron CT images were successfully reconstructed by algebraic reconstruction technique (ART) using the pre-processing projection.[Results] The results show that the structure of the object consisting of copper and PTFE was clearly reconstructed and the flaws of different holes in light material were detected.[Conclusions] The fast neutron tomography can be realized by using small accelerator neutron source.