地球和月球表面诱发伽玛辐射场及其地质响应研究

Gamma rays on the surface of the Earth and Moon can divide into natural gamma rays and induced gamma rays. The former originates from the decay of radioactive nuclei, which has been deeply investigated by some nuclear geophysicists and engineerers. The induced gamma rays originate from the nuclear reactions of primary and secondery cosmic rays with the matter of the Earth and moon. When cosmic rays,such as proton, neutron, electron and other particles, collide with the nuclei of atmosphere and soil and rocks, the gamma rays can be emmitted from the nuclei. The energys of some tpypic induced gamma rays on the surface of the Earth and Moon are 6.1294 MeV (O), 1.7788 MeV (Si),7.632 MeV(Fe)、7.646 MeV(Fe) and 0.847 MeV (Fe) etc. These induced gamma ray spectra have been succesfuly acquired with the gamma spectrometry equipped in Changer I and II satellites above the Moon. The induced gamma rays with the energy between 3.0-10.0MeV have also obtained by airborne spectrometry above the Earth. For the sake of the geological response of gamma rays on the surface of the Earth, geophysicists ussually pay attention to the gamma rays with the energy between 1.0 MeV and 3.0MeV so as to prospecting radoactive mineral resources and resolving relavant geological problems. There are a few researching papers that investigate the geological response of gamma rays between 0-1.0MeV and 3.0-10.0MeV. So, This project focuses on the theory research of the gamma radiations induced by cosmic ray on the surface of the Earth and Moon and the geological response of the gamma spectrum from 0 to 10.0MeV, including the gamma spectrum obtained from CE-1 and CE-2. The researching scopes and scientific goals in this project are as follows: 1) Investigating the spectral line charts of induced gamma rays on the surface of Earth and Moon. Detail researching items include the physical mechanism of induced gamma rays on the Earth and Moon, the technique of Monte Carlo numerical simulation; investigating the probabilities of characteristic gamma spectral lines and establishing the spectral line charts of induced gamma rays from 0 to 10.0MeV. 2) Understanding the distribution characters of continuous spectrum from 0 to 10.0MeV of induced gamma rays on the surface of the Earth and the Moon. Main researching items include the chracters of continuous induced gamma spectrum from 0 MeV to 10.0MeV, the chracters of radiactivie equilibrium spectrum from 0 to 1.0MeV and investigation some influences of potential factors on continuous induced gamma spectrum on the Earth and the Moon. 3) Determinating geological response of induced gamma spectrum on the Earth and the Moon.Main researching items include techniques stripping induced gamma spectrum from natural gamma spectrum, establishing the mathematic-physical model how to describe radiactivie equilibrium spectrum and how to reveal the relations between induced chracteristic gamma spectrum and the elemmental concentration on the Earth and the Moon.

核地球物理技术是一种重要的勘探地球物理方法。本项目以地球和月球不同类型地质体为研究对象，深入地开展地球和月球表面宇宙射线诱发伽玛辐射的理论研究和（0-1.0）兆电子伏与（3.0-10.0）兆电子伏范围的天然伽玛射线谱学研究，通过蒙特卡罗数值模拟和物理实验，构建地质体中粒子输运的随机模型，建立地球和月球表面诱发伽玛射线谱序列，研究诱发伽玛能谱的分布特征及其扰动规律。在地-空界面上，建立不同地质体上方诱发伽玛射线放射性平衡谱的状态函数和伽玛射线特征能谱的数理模型；在月-空界面上，建立轨道伽玛射线放射性平衡谱的状态函数和轨道伽玛射线特征能谱的数理模型。为我国核地球物理勘查技术和核辐射环境研究提供科学依据，也为我国月球轨道伽玛能谱数据的科学应用提供技术方法。

月球表面诱发γ辐射场特征不仅是研究月球外围辐射环境的重要依据，也是研究月球表面物质成分的重要手段。本项目深入探讨了月球浅表层介质在宇宙射线作用下形成诱发γ射线的原始谱的全谱（0~10MeV）特征和物理机理；通过蒙特卡罗数值模拟的方法，构建了宇宙射线诱发月球表面介质发射γ射线的物理模型，获取了诱发γ辐射场的原始谱特征信息；根据正电子湮灭辐射产生的物理机理，研究了通过正电子湮灭辐射通量特征正演月球表面介质有效原子序数的数理模型和反演方法；采用蒙特卡罗模拟的方法对月球表面岩石全元素（质量含量大于0.01%）诱发γ射线特征峰的通量比、不同种类岩石的质量吸收系数和CE1-GRS的相对探测效率等关键参量进行了数值模拟；结合CE1-GRS能谱数据，进行了月球表面介质的有效原子序数的反演研究和填图，并从地质角度探讨了全月有效原子序数的分布特征。研究成果可为我国绕月探测伽玛能谱数据的挖掘与科学应用提供理论依据及新的技术参考，具有重要的科学意义。