Mazunga Mohamed, Li Taosheng, Li Yanan, Hong Bing, Wang Yongfeng, Ji Xiang
University of Science and Technology of China, Hefei, Anhui 230027, China.
Key Laboratory of Neutronics and Radiation Safety, Chinese Academy of Sciences, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031, China.
Radiat Prot Dosimetry. 2017 Jul 1;175(3):413-417. doi: 10.1093/rpd/ncw368.
We have designed an extended range neutron long counter on the basis of work optimized using SuperMC code. The problem of the existing traditional long counters is that their response function falls rapidly above 5 MeV. We proposed a new designed by adding two layers of converter material inside the polyethylene moderator. The relatively low density chromium and high density lead metals convert high energy neutron by (n, xn) spallation reaction. This produces more neutrons of lower energies, which have higher probability of being detected by thermal 3He-counter. The response function at lower neutron energies was improved by inserting small polyethylene cylinder in front of 3He counter. In this design we achieved to extent the flat response function of the long counter from few keV up to 150 MeV. The total fluctuation of response curve is less than ±9% over the entire energy range. The designed long counter is suitable to be used as neutron monitor for monitoring neutron fluence at high-energy neutron source.
我们在使用SuperMC代码进行优化的工作基础上设计了一种扩展量程中子长计数器。现有传统长计数器的问题在于其响应函数在5 MeV以上迅速下降。我们提出了一种新设计，即在聚乙烯慢化剂内部添加两层转换材料。相对低密度的铬和高密度的铅金属通过(n, xn)散裂反应转换高能中子。这会产生更多较低能量的中子，这些中子被热3He计数器探测到的概率更高。通过在3He计数器前面插入小的聚乙烯圆柱体，改善了较低中子能量下的响应函数。在这种设计中，我们实现了将长计数器的平坦响应函数范围从几keV扩展到150 MeV。在整个能量范围内，响应曲线的总波动小于±9%。所设计的长计数器适用于用作中子监测器，以监测高能中子源处的中子注量。
