月球表面次生伽马与中子辐射环境模拟研究

月球表面以银河宇宙射线（GCR）为主引发的次生伽马谱和次生中子谱表征月壤的元素组成以及水冰含量，对于下一阶段的月球探测与资源原位利用是值得研究的重要内容。文章通过蒙特卡罗方法简单模拟与分析银河宇宙射线环境下月球表面簇射的伽马与中子辐射环境，结果表明：月球次生伽马谱具有明显的氢（2.23 MeV）、铝（0.83 MeV）、钙（3.53 MeV）、氧（6.13 MeV）、硅（1.77 MeV）谱线特征，水含量对其影响不大，但在高水含量时氢的谱线更为明显；月球表面次生中子谱形与月壤中水冰含量密切相关，随水冰含量增加热中子通量下降，0.01 eV中子的通量在20%含水量时比不含水时下降了72%。建议在后期月球探测计划中使用小型、低功耗的中子/伽马复合探测器，实现我国首次原位月球伽马/中子辐射环境探测，为未来进一步勘探月球原位水资源、矿产资源积累反演的基线数据。

Simulation of induced secondary gamma and neutron radiation environment on lunar surface

The secondary gamma and neutron spectra induced mainly by the galaxy cosmic rays (GCR) may represent the elementary composition and the water ice content of the lunar regolith, which has a special significance to the next phase of lunar exploration and in situ utilizations. In this paper, the Monte Carlo method is used to simulate and analyze the secondary gamma and neutron radiation on the lunar surface under the galactic cosmic ray environment. It is shown that the gamma spectrum has obvious hydrogen (2.23 MeV), aluminum (0.83 MeV), calcium (3.53 MeV), oxygen (6.13 MeV), silicon (1.77 MeV) line characteristics, with little effect of the water content, except that the hydrogen line becomes more obvious for higher water content; while the lunar neutron spectrum is closely related to the water ice content in the lunar soil in that the thermal neutron flux decreases with the increase of the water ice content. The flux of 0.01eV neutron for 20% water content decreases by 72% compared with that of the non-aqueous soil. We therefore recommend to use small, low-power neutron & gamma composite detectors in the following lunar plan to realize the in situ lunar gamma neutron radiation environment detection first in China, and to accumulate basic data for the inversion of lunar water resources and mineral resources for future explorations.