ISSN:
1588-2780
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Energy, Environment Protection, Nuclear Power Engineering
Notes:
Abstract 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02041917
