Improvements of a low-level gamma-ray spectrometry system at the underground laboratory “UDO”

The Physikalisch-Technische Bundesanstalt (PTB) operates various low-background γ-ray spectrometry systems at the underground laboratory for dosimetry and spectrometry “UDO” in the Asse salt mine. Experiences gained with these detector systems within 10 years of operation have led to technical changes and improvements of the most sensitive detector system at UDO. Key aspects are the precautions to suppress radon (and its progenies) and the performance of the detector system after exchanging the end cap. In addition, a brief summary of recent applications of this γ-ray detector system will be presented.