Transcript C-14 Dating
Radiocarbon dating Jonas Metzger and Samuel Krieg Cosmic radiation C-14 Dating Stratosphere Numbers of C-14 Atoms 100% C-14 Blend 50% 25% 12.5% 0 5'000 10'000 15'000 Time in ages C-14 C-14 C-14 C-14 C-14 C-14 C-14 C-14 C-14 C-14 Radioactive decay unstable atom Atom changed to an other Examples: - Radon changed to Polonium - Carbon changed to Nitrogen Sample preparation Cleaning of sample -> Remove contaminants Graphitisation -> Minimised sample contamination -> No cross-contamination -> Reproducible and reliable The sample is fragemented into atoms Ion source Particle accelerator 2. Mass spectrometer 1. Mass spectrometer Detector other Atoms C-14 The accelerator is a huge filter Evolution of AMS over the last 10 years 6 MV EN-Tandem 15 m 600 kV PSI/ETH system 2.5 m 200 kV system for 14C 1m Multi isotope system High precision 14C dating Biomedical 14C applications TANDY MICADAS BioMICADAS Dimensions of the new accelerator 14C 13C 12C Overview 2. filter mass analysis (low-energy end) 3. filter stripping process molecule destruction 4. filter mass analysis (high-energy end) 12C 13C / 12C 14C / 12C 1. filter negative ion formation 5. filter particle identification 13C Conclusions MICADAS... - runs very stable over time - runs unattended with low maintenance - dates samples back to 45 000 years - allows high-precision measurements Requirements for highprecision - Stability of the measuring system -> Changes in sample geometry -> Instrumental drifts -> Cross contamination -> Linearity - Reproducible sample preparation -> Sample composition (procedure blank, contamination) -> Quantity -> Sample geometry Golden Handfeste of Berne Sample Radiocarbon age δ13C (BP) (‰) Number Type +- ETH36716.1 parchment 888 20 -22.6 ETH36716.2 parchment 878 19 -20.7 ETH36716.3 parchment 882 19 -23.9 ETH36716.4 parchment 875 19 -22.3 ETH36716 parchment 881 10 -22.4 Summary Blank variation: Statistical uncertainty: < 0.5 ‰ age 1.0 - 3.0 ‰ depended Reproducibility of samples: 0.5 - 3.0 ‰ Standard normalisation: 0.5 - 1.5 ‰ Over all uncertainty: 1.5 - 5.0 ‰ relative Thank you for your attention!