Radiocarbon measurements by liquid scintillation spectrometry at the Gran Sasso National Laboratory

The background of a liquid scintillation spectrometer for radiocarbon measurements was investigated in the Gran Sasso National Laboratory (National Institute of Nuclear Physics), where 1400 m rock overburden (3800 m w.e.) absorbs most of the cosmic radiation. Comparisons were made with measurements carried out in surface laboratories (Radiocarbon Laboratory of ENEA, Bologna, Italy; PerkinElmer Life and Analytical Sciences, Turku, Finland) using Teflon and optimised copper–Teflon vials. The residual radioactivity of phototubes and the role of radon were a larger fraction of the total background signal in the Gran Sasso underground laboratory