Graphitization and AMS measurement
Radiocarbon is measured with a single stage accelerator mass spectrometer made in USA by National Electrostatics Corp. (NEC) – the world’s leader in the manufacture of electrostatic ion beam accelerator systems. The background of measurements is estimated to be 2.45 × 10−3 fM (fraction of modern carbon) using phthalic anhydride. The IAEA-C2, IAEA-C3, IAEA-C7, IAEA-C9, NIST OXII, SIRI K (carbonate) standards are used as reference materials. The 14C/12C ratio is measured with an accuracy better than 0.3% ( +/-30 years or better). For the isotopic fractionation correction the ratio of 13C to 12C is used.
All dates are calibrated by OxCal v4.4.2 (Bronk Ramsey, 2020), atmospheric data from Reimer et al., 2020.