In this paper, MCNP5 code is used to establish a landmine clearance system based on pulse fast thermal neutron method. The system prototype is modeled based on the NG-9 D-T neutron generator, which is independently developed by Northeast Normal University. Gamma rays produced by fast neutron inelastic scattering and thermal neutron capture are used to identify suspicious areas. The neutron flux passing through landmine cell before and after adding neutron reflector into initial detection system is studied. The simulation results show that the addition of a neutron reflection layer hardly improves the flux of fast neutrons passing through the landmine cell during at pulse width of 10 µs; but the thermal neutron flux through the landmine cell in the pulse interval of 90 µs is significantly increased. Among the several common reflector materials, tungsten (W) and tungsten carbide (WC) materials show better reflection performance. When W and WC are used as reflector materials and the thickness is 6 cm, the thermal neutron flux through the landmine cell is 2.00 and 1.90 times the initial value, respectively. The ratio of the thermal neutron flux in the pulse interval to the fast neutron flux during the emission of the neutron pulse increased to 0.468 and 0.444, respectively, from the initial value of 0.259. Finally, the improved model is used to simulate the landmines hidden in different depths. The results show that using 4.44 MeV and 2.22 MeV peak area counts in the region of interest can identify whether there are explosives in the detection area.

本文采用MCNP5代码建立基于脉冲快热中子法的地雷清除系统。系统原型基于东北师范大学自主研发的NG-9 DT中子发生器建模。快速中子非弹性散射和热中子俘获产生的伽马射线用于识别可疑区域。研究了在初始探测系统中加入中子反射器前后穿过地雷室的中子通量。仿真结果表明，在脉冲宽度为10μs时，增加中子反射层几乎没有提高快中子通过地雷单元的通量；但在 90 微秒的脉冲间隔内通过地雷单元的热中子通量显着增加。在几种常见的反射材料中，钨 (W) 和碳化钨 (WC) 材料显示出更好的反射性​​能。当W和WC用作反射材料且厚度为6 cm时，通过地雷单元的热中子通量分别为初始值的2.00倍和1.90倍。脉冲间隔内的热中子通量与中子脉冲发射过程中快中子通量的比值分别从初始值0.259增加到0.468和0.444。最后利用改进后的模型对埋藏在不同深度的地雷进行模拟。结果表明，在感兴趣区域使用4.44 MeV和2.22 MeV峰面积计数可以识别检测区域内是否存在爆炸物。当W和WC用作反射材料且厚度为6 cm时，通过地雷单元的热中子通量分别为初始值的2.00倍和1.90倍。脉冲间隔内的热中子通量与中子脉冲发射过程中快中子通量的比值分别从初始值0.259增加到0.468和0.444。最后利用改进后的模型对埋藏在不同深度的地雷进行模拟。结果表明，在感兴趣区域使用4.44 MeV和2.22 MeV峰面积计数可以识别检测区域内是否存在爆炸物。当W和WC用作反射材料且厚度为6 cm时，通过地雷单元的热中子通量分别为初始值的2.00倍和1.90倍。脉冲间隔内的热中子通量与中子脉冲发射过程中快中子通量的比值分别从初始值0.259增加到0.468和0.444。最后利用改进后的模型对埋藏在不同深度的地雷进行模拟。结果表明，在感兴趣区域使用4.44 MeV和2.22 MeV峰面积计数可以识别检测区域内是否存在爆炸物。脉冲间隔内的热中子通量与中子脉冲发射过程中快中子通量的比值分别从初始值0.259增加到0.468和0.444。最后利用改进后的模型对埋藏在不同深度的地雷进行模拟。结果表明，在感兴趣区域使用4.44 MeV和2.22 MeV峰面积计数可以识别检测区域内是否存在爆炸物。脉冲间隔内的热中子通量与中子脉冲发射过程中快中子通量的比值分别从初始值0.259增加到0.468和0.444。最后利用改进后的模型对埋藏在不同深度的地雷进行模拟。结果表明，在感兴趣区域使用4.44 MeV和2.22 MeV峰面积计数可以识别检测区域内是否存在爆炸物。