Sato Tatsuhiko, Niita Koji
Japan Atomic Energy Agency (JAEA), Tokai, Naka, Ibaraki, Japan.
Radiat Res. 2006 Sep;166(3):544-55. doi: 10.1667/RR0610.1.
Estimation of cosmic-ray neutron spectra in the atmosphere has been an essential issue in the evaluation of the aircrew doses and the soft-error rates of semiconductor devices. We therefore performed Monte Carlo simulations for estimating neutron spectra using the PHITS code in adopting the nuclear data library JENDL-High-Energy file. Excellent agreements were observed between the calculated and measured spectra for a wide altitude range even at the ground level. Based on a comprehensive analysis of the simulation results, we propose analytical functions that can predict the cosmic-ray neutron spectra for any location in the atmosphere at altitudes below 20 km, considering the influences of local geometries such as ground and aircraft on the spectra. The accuracy of the analytical functions was well verified by various experimental data.
估算大气中的宇宙射线中子能谱一直是评估机组人员剂量和半导体器件软错误率的关键问题。因此，我们使用PHITS代码并采用核数据库JENDL-高能文件进行了蒙特卡罗模拟，以估算中子能谱。即使在地面水平，在很宽的海拔范围内，计算得到的能谱与测量得到的能谱之间也观察到了很好的一致性。基于对模拟结果的综合分析，我们提出了分析函数，该函数可以预测海拔20公里以下大气中任何位置的宇宙射线中子能谱，同时考虑地面和飞机等局部几何形状对能谱的影响。各种实验数据很好地验证了分析函数的准确性。
