1. Radiocarbon dating Jonas Metzger and Samuel Krieg

2. Numbers of C-14 Atoms 05'00010'000Time in ages 15'000 C-14 Dating C-14 100% 50% 25% 12.5% Blend C-14 Cosmic radiation C-14 Stratosphere

3. unstable atom ‚radiation' Atom changed to an other Radioactive decay Examples: - Radon changed to Polonium - Carbon changed to Nitrogen

4. Sample preparation Cleaning of sample -> Remove contaminants Graphitisation -> Minimised sample contamination -> No cross-contamination -> Reproducible and reliable

5. Particle accelerator 2. Mass spectrometer Ion source 1. Mass spectrometer C-14 Detector other Atoms other Atoms The sample is fragemented into atoms The accelerator is a huge filter

6. 6 MV EN-Tandem600 kV PSI/ETH system200 kV system for 14 C Multi isotope system Evolution of AMS over the last 10 years High precision 14 C dating 15 m2.5 m 1 m Biomedical 14 C applications TANDYMICADAS BioMICADAS

7. Dimensions of the new accelerator 14 C 13 C 12 C 2.5 m 3.0 m

8. Overview 3. filter stripping process molecule destruction 2. filter mass analysis (low-energy end) 5. filter particle identification 4. filter mass analysis (high-energy end) 1. filter negative ion formation 13 C / 12 C 14 C / 12 C 12 C 13 C

9. Conclusions MICADAS... - runs very stable over time - runs unattended with low maintenance - dates samples back to 45 000 years - allows high-precision measurements

10. Requirements for high- precision - Reproducible sample preparation -> Sample composition (procedure blank, contamination) -> Quantity -> Sample geometry - Stability of the measuring system -> Changes in sample geometry -> Instrumental drifts -> Cross contamination -> Linearity

11. Golden Handfeste of Berne Sample Radiocarbon age δ13C NumberType(BP) +-(‰) ETH36716.1parchment88820-22.6 ETH36716.2parchment87819-20.7 ETH36716.3parchment88219-23.9 ETH36716.4parchment87519-22.3 ETH36716parchment88110-22.4

12. Blank variation: < 0.5 ‰ Statistical uncertainty: 1.0 - 3.0 ‰ Reproducibility of samples: 0.5 - 3.0 ‰ Standard normalisation: 0.5 - 1.5 ‰ Over all uncertainty: 1.5 - 5.0 ‰ age depended relative Summary

13. Thank you for your attention!