5单元中子散射相机仿真研究

Simulation research of neutron scatter camera with five units

采用粒子输运程序MCNP与FORTRAN,MATLAB程序相结合,对一种5单元结构的中子散射相机原型进行了蒙特卡罗模拟,对252 Cf裂变中子源进行了图像、能量的重建。结果表明:该相机的能量分辨力为9%左右,角分辨与闪烁体的体积有关;中子能量为2MeV左右时,散射相机的探测效率达到最大值;源的距离、闪烁体尺寸、前后面板距离、事件数等对重建图像的分辨力都有不同程度的影响;散射相机可以获得裂变中子源的能谱形状,但系统的结构、探测阈值等会使能谱测量造成一定的偏差。该理论工作的结论可推广到由更多单元组成的散射相机中使用。

As a neutron detecting and imaging device used for detection of special nuclear material （SNM）, the newly repor ted neutron scatter camera can acquire the neutron position and energy information simultaneously. In this paper, the particle transport code MCNP was used together with the program MATLAB and Fortran to simulate a five units prototype of a neutron scatter camera, and to reconstruct the image and energy of a ^252Cf neutron source. The calculation results show that the camera＇ s energy resolution is about 9 % and its angular resolution is related to the size of the scintillators; when the neutron energy equals 2 MeV, the detection efficiency reaches a maximum; the distance of the source, the size of the scintillators, the distance between the front and rear surfaces of the detectors, and the number of the events have influence on the resolution of the image to a certain extent; the scatter camera can measure the fission neutron energy spectrum, but the factors such as the camera＇s structure and detection threshold could result in some inaccuracy of the measurement. This simulation work lays a foundation for further experi- mental research, and its conclusion can be generalized to the neutron scatter camera with much units.