中文摘要：

提出了一种由聚乙烯（Polyethylene, PE）转换器、微通道板（Microchannel Plate, MCP）电子增强器和 CCD （Charge-Coupled Device）相机组成的快中子照相像探测器新方案。采用 Geant4软件模拟研究了14.5 MeV 快中子入射在 PE 转换器上的出射质子产额、能谱随 PE 厚度的变化规律，确定了 PE 转换器的厚度范围和转换效率等重要参数。模拟结果显示，PE 转换器的厚度应该选择在2.5 mm 左右，此时的转换效率约为0.37%。采用Geant4软件模拟了14.5 MeV 快中子入射在 PE 转换器的质子输运和质子在 MCP 中电子的产生和倍增过程，给出了 MCP 输出的电子束斑图像。模拟结果显示，由 PE 和 MCP 组成的转换器系统能将入射的快中子转换成电子束斑点阵信息，各电子束斑之间的界限清晰，单孔电子束斑直径略大于 MCP 孔径，即电子束斑点阵像素可以达到 MCP 孔径量级。

英文摘要：

Background： As a unique non-destructive testing technique, fast neutron radiography has been widely concerned in recent years. However, the fast neutron imaging detector with higher resolution and higher detection efficiency still needs to be researched. Purpose： A new fast neutron imaging detector consisting of a polyethylene （PE） converter and a microchannel plate （MCP）, is proposed for 14.5-MeV fast neutron radiography. Simulation studies are conducted for the design aim. Methods： The yields and energy spectra of the recoil proton produced by 14.5-MeV fast neutron on the PE converter are simulated using Geant4 code. The yields and the energy spectra of the recoil proton under the different PE converter thicknesses are presented in order to determine the converter efficiency and the reasonable thickness of the PE converter. Less than 14.5 MeV, fast neutron incident, the electronic gain process in MCP is simulated using Geant4 code. In order to analyze spatial resolution, the electron beam spot images are recorded after MCP. Results： The simulation results show that the thickness of PE converter should be selected in the range of 2.5 mm, and the converter efficiency is about 0.37%. The electron images show that the electron beam spot diameter is slightly bigger than MCP aperture. Conclusion： It can be predicted that the spatial resolution of the detector is close to MCP aperture.