With exciting new NASA plans for a sustainable return to the moon, astronauts will once again leave Earth's protective magnetosphere only to endure higher levels of radiation from galactic cosmic radiation (GCR) and the possibility of a large solar particle event (SPE). Gateway, lunar landers, and surface habitats will be designed to protect crew against SPEs with vehicle optimization, storm shelter concepts, and/or active dosimetry; however, the ever penetrating GCR will continue to pose the most significant health risks especially as lunar missions increase in duration and as NASA sets its aspirations on Mars. The primary risks of concern include carcinogenesis, central nervous system (CNS) effects resulting in potential in-mission cognitive or behavioral impairment and/or late neurological disorders, degenerative tissue effects including circulatory and heart disease, as well as potential immune system decrements impacting multiple aspects of crew health. Characterization and mitigation of these risks requires a significant reduction in the large biological uncertainties of chronic (low-dose rate) heavy-ion exposures and the validation of countermeasures in a relevant space environment. Historically, most research on understanding space radiation-induced health risks has been performed using acute exposures of monoenergetic single-ion beams. However, the space radiation environment consists of a wide variety of ion species over a broad energy range. Using the fast beam switching and controls systems technology recently developed at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory, a new era in radiobiological research is possible. NASA has developed the "GCR Simulator" to generate a spectrum of ion beams that approximates the primary and secondary GCR field experienced at human organ locations within a deep-space vehicle. The majority of the dose is delivered from protons (approximately 65%-75%) and helium ions (approximately 10%-20%) with heavier ions (Z ≥ 3) contributing the remainder. The GCR simulator exposes state-of-the art cellular and animal model systems to 33 sequential beams including 4 proton energies plus degrader, 4 helium energies plus degrader, and the 5 heavy ions of C, O, Si, Ti, and Fe. A polyethylene degrader system is used with the 100 MeV/n H and He beams to provide a nearly continuous distribution of low-energy particles. A 500 mGy exposure, delivering doses from each of the 33 beams, requires approximately 75 minutes. To more closely simulate the low-dose rates found in space, sequential field exposures can be divided into daily fractions over 2 to 6 weeks, with individual beam fractions as low as 0.1 to 0.2 mGy. In the large beam configuration (60 × 60 cm2), 54 special housing cages can accommodate 2 to 3 mice each for an approximately 75 min duration or 15 individually housed rats. On June 15, 2018, the NSRL made a significant achievement by completing the first operational run using the new GCR simulator. This paper discusses NASA's innovative technology solution for a ground-based GCR simulator at the NSRL to accelerate our understanding and mitigation of health risks faced by astronauts. Ultimately, the GCR simulator will require validation across multiple radiogenic risks, endpoints, doses, and dose rates.

中文翻译：

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NASA的第一个地面银河宇宙射线模拟器：开启太空放射生物学研究的新纪元。

随着令人兴奋的新NASA计划可持续地返回月球，宇航员将再次离开地球的保护性磁层，仅能承受来自银河宇宙辐射（GCR）的更高水平的辐射以及发生大太阳粒子事件（SPE）的可能性。通道，月球着陆器和地面栖息地将通过车辆优化，防风雨概念和/或主动剂量测定来保护机组人员免受SPE的侵害；但是，不断渗透的GCR将继续构成最重大的健康风险，尤其是随着登月任务的持续时间增加以及NASA将火星寄予厚望。引起关注的主要风险包括致癌作用，中枢神经系统（CNS）效应，导致潜在的任务中认知或行为障碍和/或晚期神经系统疾病，包括循环系统和心脏病在内的组织退化性影响，以及潜在的免疫系统下降都会影响船员健康的多个方面。要表征和减轻这些风险，需要大幅度减少长期（低剂量率）重离子暴露的生物学不确定性，并确认相关空间环境中的对策。从历史上看，大多数了解空间辐射引起的健康风险的研究都是使用单能单离子束的急性暴露进行的。但是，空间辐射环境由能量范围很广的各种离子组成。使用布鲁克海文国家实验室（NASH）的NASA空间辐射实验室（NSRL）最近开发的快速光束切换和控制系统技术，放射生物学研究的新时代是可能的。NASA开发了“ GCR模拟器”来生成离子束光谱，该光谱近似于在深空飞行器中人体器官位置经历的一次和二次GCR场。大部分剂量来自质子（约65％-75％）和氦离子（约10％-20％），重离子（Z≥3）贡献其余部分。GCR仿真器将最先进的细胞和动物模型系统暴露给33个连续束，其中包括4个质子能加降解物，4个氦能加降解物以及5个C，O，Si，Ti和Fe重离子。聚乙烯降解系统与100 MeV / n H和He束一起使用，可提供几乎连续的低能粒子分布。500 mGy的辐射，从33束光束中的每束发出剂量，需要大约75分钟。为了更精确地模拟太空中的低剂量率，可以将连续的野外照射分为2至6周的每日部分，单个射线部分低至0.1至0.2 mGy。在大光束配置（60×60 cm2）中，有54个特殊的笼子可以容纳2至3只老鼠，每只大约持续75分钟，或者容纳15只单独饲养的老鼠。2018年6月15日，NSRL通过使用新的GCR模拟器完成了首次运行，取得了重大成就。本文在NSRL上讨论了NASA针对地面GCR模拟器的创新技术解决方案，以加快我们对航天员面临的健康风险的了解和缓解。最终，GCR仿真器将需要对多种放射风险，终点，剂量和剂量率进行验证。