Low-background Germanium spectrometry the bottom line three years later
Low-background Germanium spectrometry the bottom line three years later
复制标题
低本底锗光谱测定三年后的底线
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
F. Avignone
中科院分区：
文献类型：
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作者：
R. Brodzinski;H. Miley;J. H. Reeves;F. Avignone
三年前，人们讨论了最先进的低本底锗光谱测定法，并对剩余本底的来源提出了推测。其中一些猜测已被证明是错误的。现代铅屏蔽含有约 100 Bq/kg 的 210 Pb。我们 450 年历史的铅含量<100 mBq/kg 将高纯度电铸铜马里内利屏蔽放置在探测器周围，对背景没有影响，这意味着源不是 450 年历史的屏蔽。这种旧铅屏蔽中 210Pb 的新限值为 <9 mBq/kg。电铸铜部件被发现含有 226Ra 和 228Th 污染物，含量分别为 3500 和 110 μBq/kg。电铸浴中的高纯度 H2SO4、重结晶 CuSO4 和 BaSO4 清除剂已将这些污染物分别降低至 <25 和 9 μBq/kg。在铜中，宇宙射线诱发的核反应现在是放射性的主要来源。例如，仅在海平面暴露 24 小时后即可轻松测量 58Co。已制造出含有 2150 克 87.44% 富集 76Ge 的新型锗光谱仪，以减轻背景中宇宙成因 68Ge 的影响。提供了当前的背景光谱，并确定了潜在的来源。
Three years ago, state-of-the-art low-background germanium spectrometry was discussed, and speculations were advanced as to the origin of the remaining background. Some of those speculations have been shown to the incorrect. Contemporary lead shielding contains ≈ 100 Bq/kg of210Pb. Our 450-year-old lead was shown to contain <100 mBq/kg A high purity electroformed copper Marinelli shield was placed around the detector with no efffect on the background, which implied that the source is other than the 450-year-old shield. A new limit on the210Pb in this old lead shield is <9 mBq/kg. Electroformed copper components were found to contain226Ra and228Th contaminations at levels of 3500 and 110 μBq/kg, respectively. High purity H2SO4, recrystallized CuSO4, and a BaSO4 scavenge in the electroforming bath have reduced these contaminations to <25 and 9 μBq/kg, respectively. In copper, cosmic ray induced nuclear reactions are now the dominant source of raioactivity. For example,58Co can be readily measured after only a 24-hour exposure at sea level. A new germanium spectrometer containing 2150 grams of 87.44% enriched76Ge has been fabricated to mitigate the effect of cosmogenic68Ge in the background. Current background spectra are presented, and potential sources identified.