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Abstract

The background of a low-level high-purity Ge detection system has been reduced by placing it into an underground research facility at Mol (Belgium) at a depth of about 225 m, which corresponds to approximately 500 m water equivalent. At ground level a sophisticated lead shield surrounded the 100 cm3 germanium crystal and reduced the background radioactivity, within the energy interval 3 to 2800 keV, by a factor of 100. An integrated count rate of (0.609 +/- 0.001)/s was achieved over this energy interval, which was mainly attributable to the influence of cosmic rays. The entire system (including lead shield) was transferred to the underground laboratory; the influence of radon was eliminated by an electrolytic copper shield. The final integrated count rate, achieved over the energy interval 3 to 2800 keV of (0.00666 +/- 0.00006)/s represents an additional reduction factor of 91, again mainly attributable to the influence of cosmic rays. Background count rates of selected energy regions of interest are given, in order to compare the background of different Ge-systems, and to demonstrate the reduction of neutron activation peaks and the improvement of the sensitivity to particular radionuclides. Applications of the system and possible ways to improve its performance are discussed.

Additional information

Authors: WORDEL R, JRC Geel (BE);MOUCHEL D, JRC Geel (BE);BONNE A, SCK/CEN, Mol (BE);MEYNENDONCKX P, SCK/CEN, Mol (BE);VANMARCKE H, SCK/CEN, Mol (BE)
Bibliographic Reference: Paper presented: Third International Summer School on Low-Level Measurements of Radioactivity in the Environment : Techniques and Applications, Huelva (ES), September 20 - October 2, 1993
Availability: Available from (1) as Paper EN 37893 ORA
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