Natural Gamma-ray Activity of Cores of the KTB Pilot Hole VB1

In the laboratory, the gamma radiation is measured by a sodium iodtite (NaI) scintillation detector (cores and cuttings) and by a germanium (Ge) semiconductor detector (cuttings).
The cuttings are measured in air tight Marinelli-beakers with a volume of 250 cm3. For the core measurements a special, automatically operating equipment with three NaI detectors is used. A description of this apparatus is given in Wienand et al. (1989). The principle of measurements with the Ge-detector is described by Bücker et al. (1991).The measured spectra are calibrated by a standard of Luvarovite (NIM-L, South African Bureau of Standards). The influence of the local terrestrial radiation on the measurements has been corrected. Especially for the core measurements a calibration procedure has been performed for geometric corrections (core diameter and length). In general, a measuring time of 12 h for the NaI-detector and 2 h for the Ge-detector was chosen.