摘要: 为了提高PGNAA系统中D-T中子管的中子慢化效率，获得更高的热中子产额，借助蒙特卡罗模拟，确定了以铅为中子反射层、5个聚乙烯层和铅层相互交替作为中子慢化层、碳化硼含量为3%的含硼聚乙烯作为中子吸收层以及铅作为γ屏蔽层的中子慢化装置模型。针对中子产额为3×107 n/s 的D-T中子管，该慢化装置输出面低于5 eV中子通量可达5.28×106 n/s，占总中子通量的30.8%，有效提高了中子慢化效率。经过验证模拟结果能够满足实验要求。

To improve the moderating efficiency of D-T Neutron Generator in PGNAA system, and get higher thermal neutron yield, the Monte Carlo code MCNP was used to optimize the moderation setup. The lead was selected as neutron reflector and gamma absorber, 5 polyethylene layers and 4 lead layers constituted the neutron moderator and 3% boron-doping polyethylene was selected as neutron absorber. For the yield of 3107 n/s D-T Neutron Generator, this moderation setup can provide a yield of lower than 5 eV of 5.28106 n/s, accounting for 30.8% of total neutron yield, dramatically improves the moderating efficiency. It is proved that the simulation results can satisfy the requirement of PGNAA system by preliminary experimental verification.