Applicability of prompt gamma-ray analysis to the initial analysis of the extraterrestrial materials for chemical composition
Applicability of prompt gamma-ray analysis to the initial analysis of the extraterrestrial materials for chemical composition
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即时伽马射线分析在地外物质化学成分初步分析中的应用
DOI：
10.1186/bf03351702
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Y. Oura
中科院分区：
文献类型：
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作者：
M. Ebihara;Y. Oura
当未来的太空任务将地外物质带回地球时，这些物质将受到初步检查。出于这种目的，测量应是非破坏性的。在这项研究中，我们研究了非破坏性提示伽马射线分析（PGA）在确定回收材料化学成分中的适用性，重点研究了诱发放射性水平以及PGA对同位素组成的影响。在日本原子能研究所的PGA设施的当前条件下，在适当冷却后基本上没有残留的放射性物质，使得PGA分析的同一样品可以不受任何限制地用于进一步的研究。研究了PGA对235U中子诱导反应和中子诱导核裂变同位素组成的影响。即使对于某些惰性气体核素，如80Kr和128I，中子诱导反应也不会带来明显的影响，相邻卤素上的（n, γ）反应可以增强这种影响。中子诱导的235U核裂变反应基本上对同位素组成没有影响。此外，与仪器中子活化分析（INAA）和同步辐射x射线荧光（SR-XRF）等其他无损分析方法相比，PGA具有许多优点；INAA留下了大量的诱导放射性，SR-XRF产生的元素组成值不太可靠，也不太准确。综上所述，PGA是一种最适合用于空间返回样品初始分析的分析方法。
When extraterrestrial materials are returned to the earth by future space missions, these materials are to be subjected to the initial examination. For such purposes, measurements are desired to be done non-destructively. In this study, we investigated the applicability of non-destructive prompt gamma-ray analysis (PGA) for determining chemical composition of the returned materials, focusing on levels of induced radioactivities and the effect on isotopic composition by PGA. Under current conditions applied for the PGA facility at the Japan Atomic Energy Research Institute, essentially no residual radioactivities remain after appropriate cooling, making the same specimen analyzed by PGA usable for further research without any restriction. The effect on isotopic composition by PGA was examined both for neutron-induced reactions and for neutron-induced nuclear fission of 235U. No significant effect can be brought by neutron-induced reactions even for some noble gas nuclides such as 80Kr and 128I, which can be augmented by (n, γ) reactions on neighboring halogens. Neutron-induced nuclear fission reactions of 235U yield essentially no effect on isotopic composition. In addition, PGA has several advantages over other nondestructive analytical methods such as instrumental neutron activation analysis (INAA) and synchrotron radiation x-ray fluorescence (SR-XRF); INAA leaves a significant level of induced-radioactivities and SR-XRF yields less reliable and less accurate values for elemental composition. Judging from these features and characteristics, it is concluded that PGA can be one of the most suitable analytical methods potentially applicable for initial analysis of returned samples from space.