Measurement of the 14C abundance in a low-background liquid scintillator

The ¹⁴C/¹²C ratio in 4.8 m³ of high-purity liquid scintillator was measured at (1.94±0.09)×10⁻¹⁸, the lowest ¹⁴C abundance ever measured.  At this level the spectroscopy of low-energy solar neutrinos, in particular a measurement of the ⁷Be neutrino flux, will not be obstructed by the ¹⁴C β decay intrinsic to a liquid scintillator detector. A comprehensive study of the deviation of the shape of the ¹⁴C β spectrum from the allowed statistical shape reveals consistent results with recent observations and calculations. Possible origins of the ¹⁴C in the liquid scintillator are discussed.