轨道伽马能谱中湮灭辐射定量分析与岩性反演方法研究

轨道伽马能谱是深空探测的重要手段之一，在我国深空探测深度和广度不断拓展的背景下，开展相关新内容、新方法研究，具有重要的科学和现实意义。湮灭辐射承载有效地质信息，却尚未对其实现定量分析和科学应用。主要原因是：“宇宙射线级联簇射”和“质子-中子-伽马-电子对效应”均能产生湮灭辐射，在0.511MeV能窗内谱线剥离难度较大；缺少准确、有效的实验手段对数理模型进行标定。本课题拟通过：1、以月表湮灭辐射产生、输运机理入手构建数理方程；2、采用Geant4仿真CE1-GRS探测过程宇宙射线能谱，以控制各反应通道开-闭的方法，对“级联簇射”和“质子-中子-伽马-电子对效应”所致湮灭辐射逐一剥离；3、依托“中国原子能科学研究院‘强流质子回旋加速器’”开放平台开展实验，修正数理方程，标定岩性识别模型；最终实现“湮灭辐射反演岩性”的新应用，为深空轨道伽马能谱探测发展提供参考。

Orbital gamma spectrum is one of the significant means of deep space exploration. In the context of the expanding depth and breadth of deep space exploration in China, it is of great scientific and practical significance to carry out some research on new contents and methods. The positron annihilation radiation, in lunar orbit gamma ray spectrum, can reflect a wealth of information about the physical properties and chemical composition. While, it is very difficult to accomplish the quantitative analysis for the positron annihilation radiation, since the annihilation radiation is extremely complex. In this project, we plan to study the key technologies for calculating the positron annihilation radiation fluence rate accurately. Firstly, The distribution of positron fluence rate in near-lunar orbit and background in low energy range are acquired by Monte Carlo simulation. Then we try to carry out the experimental study on cascade shower of cosmic rays, by proton accelerator, which is used to calibrate the inversion model. Finally, the scientific goal of lunar lithology inversion is achieved. This project is beneficial to explore the scientific value of lunar orbital energy spectrum data.