Low-level γ-ray spectrometry at the underground laboratory Garching

• Published in: Applied radiation and isotopes Vol. 91; pp. 49 - 56
• Main Authors: Sivers, M.v., Hofmann, M., Mannel, T., Feilitzsch, F.v., Oberauer, L., Potzel, W., Scho¨nert, S.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2014
• Subjects: HPGe detectors; Low-level gamma-ray spectrometry; Underground laboratory; Low-level gamma-ray spectrometry; Underground laboratory; HPGe detectors
• ISSN: 0969-8043; 1872-9800
• DOI: 10.1016/j.apradiso.2014.05.010

Two low-background setups for material screening based on HPGe detectors were built in the Garching Underground Laboratory with an overburden of ~10m.w.e. They include several layers of passive shielding as well as an active muon veto. The first setup (GEM) comprises a 150% efficiency HPGe detector which can optionally be surrounded by a NaI(Tl) scintillation detector that serves as anti-Compton veto. The second setup (LoAx) consists of two smaller HPGe detectors which are arranged face-to-face to cover a larger solid angle around the sample and to allow coincidence measurements. For a 5.6kg piece of copper after 11 days of measurement we have reached a sensitivity for 226Ra and 228Ra/228Th of ~5mBqkg−1 with the GEM setup. In the LoAx setup we have achieved limits of less than 100mBqkg−1 for 234Th and 210Pb with a 156g sample of PPO wavelength shifter after 18 days of measurement. •Two setups for low-level γ-ray spectrometry were built.•The background count rate between 100 and 2700keV is 5700day−1.•Sensitivities of 5mBq/kg were achieved for 226Ra and 228Th.•Sensitivities of less than 100mBqkg−1 were achieved for 210Pb and 234Th.