Abstract

Ambient gamma radiation levels due to natural and anthropogenic sources play an important role in low level gamma spectrometric measurements of different sample matrices. Minimum detection level (MDL) of a high-resolution gamma spectrometry system directly depends on the background radiation levels. The variation of background radiation level due to the location (surface level or below ground level) of the laboratory housing the gamma spectrometric system and the impact of different shielding types is discussed in this study. Relocation of the system to a below ground level laboratory significantly brought down the background induced due to cosmic components. Corresponding reduction in count rates for major gamma emitters ranged from 36 to 59%. Consequently, the MDLs for corresponding peaks improved by 20 to 36%. Improvising the lead bricks-based passive shielding for the gamma spectrometry system to circular lead ring with graded Cu+Sn lining minimised the gamma background due to streaming of gamma rays through lead bricks and reduced the overall background. The combined effect of the location of laboratory below ground level and graded lead shielding resulted in reduction of MDL of the gamma spectrometry system for major gamma peaks by 54 to 80%.

中文翻译：

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低能伽马射线谱测量中位置和屏蔽对伽马辐射背景的影响

摘要

自然和人为源造成的环境伽马辐射水平在不同样品基质的低水平伽马能谱测量中发挥着重要作用。高分辨率伽马能谱测定系统的最低检测水平 (MDL) 直接取决于背景辐射水平。本研究讨论了由于安装伽玛能谱系统的实验室的位置（表面水平或地下水平）引起的背景辐射水平的变化以及不同屏蔽类型的影响。将系统搬迁到地下实验室显着降低了由宇宙成分引起的背景。主要伽马发射体的计数率相应降低了 36% 至 59%。因此，相应峰的 MDL 提高了 20% 至 36%。将伽马能谱系统的基于铅砖的被动屏蔽改进为具有渐变 Cu+Sn 衬里的圆形铅环，最大限度地减少了伽马射线流过铅砖造成的伽马背景，并降低了整体背景。实验室位于地面以下的位置和分级铅屏蔽的综合作用导致伽马能谱测量系统主要伽马峰的 MDL 降低了 54% 至 80%。