Untergrundlaboratorium für Messungen geringer Radioaktivität

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Abstract
An underground laboratory has been installed under 47 m rock covering (125 metres water equivalent), where the cosmic radiation ist diminished more than 40-fold. The massive laboratory building, 6 × 3.5 m2 by 3.4 m height, was erected on a foundation of 0.8 m serpentinite with a framework of old steel, forming walls and ceiling with 0.7 m thickness, filled with serpentinite. A Ge(Li)-detector of 75 m3 and 9.1% efficiency ist shielded by lead of 10 cm thickness. The background spectra are comparable with those of anticoincidence devices described in the literature. Detection limits for small samples amount to 0.025 Bq; for natural radioactivities of 1000 g samples to 0.15 ppm Th, 0.03 ppm U and 0.011% K2O for 12 h-measurements.