月表岩石诱发γ辐射场原始谱特征模拟

Simulation study on original characteristic spectrum of gamma radiation field cosmic-induced on lunabase rocks

玄武岩、克里普岩、橄榄岩在月球表面广泛分布,并具有一定的代表性,并且岩石密度差异较大,高能粒子(Galactic Cosmic Rays,GCR;Solar Particle Event,SPE)与岩石相互作用后激发γ射线。利用蒙特卡罗软件FLUKA开展了月表高能质子诱发γ射线的研究,获取了月表多种成岩主元素的特征γ射线能量峰、正电子湮灭峰和γ辐射平衡峰等原始谱特征信息。通过数据分析表明特征峰强度与月表岩石密度呈正相关。原始谱特征的研究不仅可以为不同系列绕月γ数据的对比研究提供参考,也可为在全月表面进行基于核辐射方法的岩石密度填图研究提供理论支撑。

Background： With large differences in mass density, Basalt, KREEP and Dunite are representative and widely distributed on lunar surface. Cosmic-inducedg-ray is produced after energetic particles （Galactic Cosmic Rays, GCR; Solar Particle Event, SPE） impacting on lunabase rocks.Purpose：This study aims at discovering the factors of cosmic-inducedg-ray spectrum and then utilizing the gamma ray data for lunar exploration more efficiency.Methods： A Monte Carlo model for proton-induced gamma ray is designed for the FLUKA simulation software to research cosmic-induced gamma original spectrum. Data analysis is applied to find the relationship between the characteristic spectrum and the densities of lunabase rocks.Results： The model is appropriate to simulate cosmic-inducedg-ray original spectrum. A great variety of original spectrum characteristics, such as energies of main elements, positron annihilation peak and radiation balanced peak, are acquired.Conclusion： A positive correlation is found between mass density of lunabase rock and characteristic peak intensity. These researches for original spectrum can be applied to comparing different lunar gamma-ray spectrum and rock mass density mapping on lunar surface as a reference.