摘要
利用蒙特卡罗(MC)粒子输运程序MCNPX分别计算了用238U裂变电离室测量由加速器产生的14.8 MeV和25.5 MeV准单能中子注量率以及将其推广应用于测量散裂中子源和宇宙中子源的中子注量率时,由电离室结构、电离室气体、空气等引起的对探测器裂变计数率的修正因子,并给出了探测器在各种情况下的探测响应。为解决蒙特卡罗模拟中探测片太薄、统计误差过大的问题,计算中采用了Dxtran球和强迫碰撞两种方差减少技巧,以降低统计误差、提高计算效率。对于源中子谱覆盖范围较宽、抽样效率低的情况,采用了高能和低能两部分能谱分别计算的方法,以提高计算效率。将模拟计算得到的修正因子应用于探测响应的理论公式,得到相应的探测响应,并与MC模拟计算直接得到的探测响应进行了比较,对模拟计算进行自洽性验证。利用伴随α粒子测量装置和电离室同时测量14.8 MeV准单能中子注量率,得出238U裂变电离室对串列加速器上14.8 MeV准单能中子场的探测响应,与MC模拟计算结果进行比较,对模拟计算进行实验验证。
The Monte-Carlo (MC) code MCNPX was used for the calculation of the correction factors caused by the chamber geometric structure, the ionized gas and air when a ^238U fission chamber is used to determine the neutron fluence rate of 14.8 MeV and 25.5 MeV quasi-monoenergetic neutrons produced by 5SDH-2 and HI-13 tandem accelerators, the cosmic neutron source and the spallation neutron source. The detection responses for these neutrons were also given. Because the sensitive layer of the detector is too thin, the Dxtran spheres and force collisions were calculation efficiency and to reduce the variance. In the case combined to of the energy improve the range of the source spectrum is wide and high or low energy particles are infrequent such as the cosmic neutron source or the spallation neutron source, the higher energy part and the lower energy part were calculated separately to improve the calculation efficiency. Finally, the correction factors were used for the calculation of the detection response with formula, and the detection responses calculated with formula and by MC simulation were compared with each other. The detection response of the ^238U fission chamber for 14.8 MeV neutrons was also calibrated by the associated particle method. The measured result was compared with the calculated one from MC simulation.
出处
《原子能科学技术》
EI
CAS
CSCD
北大核心
2009年第3期208-214,共7页
Atomic Energy Science and Technology