Status report: Implementation of gas measurements at the MAMS 14C AMS facility in Mannheim, Germany

By implementing a Gas Interface System (GIS), CO2 gas measurements for radiocarbon dating of small environmental samples (<100 µgC) have been established at the MICADAS (Mini Carbon Dating System) AMS instrument in Mannheim, Germany. The system performance has been optimized and tested with respect to stability and ion yield by repeated blank and standard measurements for sample sizes down to 3 µgC. The highest 12C− low-energy (LE) ion currents, typically reaching 8-15 µA, could be achieved for a mixing ratio of 4% CO2 in Helium, resulting in relative counting errors of 1-2% for samples larger than 10 µgC and 3-7% for sample sizes below 10 µgC. The average count rate was ca. 500 counts per microgram C for OxII standard material. The blank is on the order of 35,000-40,000 radiocarbon years, which is comparable to similar systems. The complete setup thus enables reliable dating for most environmental samples (>3 µgC).