a GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany.
b Trento Institute for Fundamental Physics and Applications (TIFPA), Povo, Italy.
Radiat Res. 2019 Feb;191(2):154-161. doi: 10.1667/RR15123.1. Epub 2018 Nov 30.
The harmful effects of space radiation pose a serious health risk to astronauts participating in future long-term missions. Such radiation effects must be considered in the design phase of space vessels as well as in mission planning. Crew radioprotection during long periods in deep space (e.g., transit to Mars) represents a major challenge, especially because of the strong restrictions on the passive shielding load allowed on-board the vessel. Novel materials with better shielding performance compared to the "gold standard" high-density polyethylene are therefore greatly needed. Because of the high hydrogen content of hydrides, lithium hydride has been selected as a starting point for further studies of promising candidates to be used as passive shielding materials. In the current experimental campaign, the shielding performance of lithium hydride was assessed by measuring normalized dose, primary beam attenuation and neutron ambient dose equivalent using 430 MeV/u C, 600 MeV/u C and 228 MeV proton beams. The experimental data were then compared to predictions from the Monte Carlo transport codes PHITS and GRAS. The experimental results show an increased shielding effectiveness of lithium hydride compared to reference materials like polyethylene. For instance, the attenuation length for 600 MeV/u C primary particles in lithium hydride is approximately 20% shorter compared to polyethylene. Furthermore, the comparison results between both transport codes indicates that the standard Tripathi-based total reaction cross-section model of PHITS cannot accurately reproduce the presented experimental data, whereas GRAS shows reasonable agreement.
太空辐射的有害影响对参与未来长期任务的宇航员的健康构成严重威胁。在设计太空飞船以及规划任务时，必须考虑这种辐射效应。在深空（例如，前往火星的途中）长时间内对机组人员进行辐射防护是一项重大挑战，这主要是因为对船上允许的被动屏蔽负荷有很强的限制。因此，非常需要具有比“高密度聚乙烯”标准更好屏蔽性能的新型材料。由于氢化物具有高氢含量，因此选择氢化锂作为进一步研究有前途的候选材料作为被动屏蔽材料的起点。在当前的实验活动中，使用 430 MeV/u C、600 MeV/u C 和 228 MeV 质子束通过测量归一化剂量、初级束衰减和中子环境剂量当量来评估氢化锂的屏蔽性能。然后将实验数据与蒙特卡罗输运代码 PHITS 和 GRAS 的预测进行比较。实验结果表明，氢化锂与聚乙烯等参考材料相比，具有更高的屏蔽效率。例如，在氢化锂中，600 MeV/u C 初级粒子的衰减长度比聚乙烯短约 20%。此外，两种输运代码之间的比较结果表明，PHITS 的基于标准 Tripathi 的总反应横截面模型不能准确地再现所呈现的实验数据，而 GRAS 则显示出合理的一致性。
