AI 中文总结
该研究基于GEANT4模拟，通过用质子束照射火星大气，体素化风化层，放置表面探测器等步骤，揭示氢对火星表面中子和伽马能谱的影响，发现风化层是主要辐射源，且反照率中子各能段能观测到氢，质子输运等对氢不敏感。
AI 中文摘要
受银河宇宙射线质子与火星大气及风化层在有无氢情况下相互作用的启发，本研究采用一系列GEANT4模拟，以揭示氢对火星表面次级和反照率中子以及相关伽马射线能谱的影响。用平面垂直PAMELA质子束照射火星大气，先获得初级质子谱在大气中的衰减以及质子在风化层中的射程和能量沉积。将风化层体素化为100个2厘米厚的单元，获取有无0.11 wt.%氢时产生的中子和伽马射线的深度分布以及到达表面的大气产生的中子和伽马射线的动能谱。最后在风化层顶部放置表面探测器，比较大气产生的中子和伽马能谱与表面探测器记录的总中子和伽马能谱，评估大气和风化层对到达火星表面的总辐射场的相对贡献。还获得了热中子、超热中子和快中子的反照率中子能谱。GEANT4模拟表明，到达火星表面的中子和伽马射线主要来源是火星风化层而非仅大气，火星表面反照率中子的各能量段都能观测到0.11 wt.%氢的存在，而质子输运以及中子和伽马的总体产生深度分布对氢相对不敏感，这表明火星风化层的元素变化。
英文摘要
Motivated by the interactions of the GCR protons with the Martian atmosphere and regolith in the absence and presence of hydrogen, a series of GEANT4 simulations are employed in this study to reveal the influence of hydrogen on the energy spectra of secondary and albedo neutrons together with the associated gamma rays at the Martian surface. Following irradiation of the Martian atmosphere with a planar vertical PAMELA proton beam, the attenuation of the primary proton spectrum through the atmosphere and the range and energy deposition of protons within the regolith are first obtained. The depth profile of the generated neutrons and gamma rays, along with the kinetic energy spectra of the atmospherically produced neutrons and gammas reaching the surface, is then acquired in the absence and presence of 0.11 wt.% hydrogen by voxelizing the regolith into 100 cells of 2-cm thickness. Finally, a surface detector is placed atop the regolith, and the atmospherically produced neutron and gamma spectra are compared with the total neutron and gamma spectra recorded at the surface detector to assess the relative contribution of the atmosphere and the regolith to the overall radiation field reaching the Martian surface. The energy spectra of the albedo neutrons are also obtained in terms of thermal, epithermal, and fast neutrons. The GEANT4 simulations show that the Martian regolith, rather than the atmosphere alone, constitutes the dominant source of the neutron and gamma population arriving at the surface, and that the presence of 0.11 wt.% hydrogen is observable in each energy regime of the albedo neutrons at the Martian surface, while proton transport and the overall neutron and gamma production depth profile remain comparatively insensitive to hydrogen, thereby indicating the elemental variation of the Martian regolith.
Comments13 pages, 7 figures, 2 tables
