On the use of mercury as a means of locating background sources in ultra low-background HPGe-detector systems

In low-level gamma-ray spectrometry, it is common to measure large samples in order to obtain low detection limits for the massic activity (in mBq/kg). These samples have significant shielding effects. In order to study whether the background sources in three ultra low-background HPGe detectors were located in the detector or in the shield, Marinelli beakers filled with hyperpure mercury were measured. Although the measurements were hampered by the presence of cosmogenically produced 194Hg, information regarding the major background location of 40K, 60Co, 137Cs, 210Pb, 226Ra, 228Ra and 228Th could be obtained.