AMS measurements from microgram to milligram

A gas handling system was developed to establish radiocarbon measurements of carbon masses below 100 μg. In this system, CO2 originating from an elemental analyzer, is cryogenically stored and thereafter directly fed into a gas ion source. In Erlangen, we have a hybrid ion source (40 sample MGF-SNICS) for measuring graphite samples as well as CO2 samples. The advantage of using gas samples is the minimized carbon contamination during the target production due to the shortened sample preparation and the higher efficiency of produced negative carbon ions from CO2. This enables to measure samples with carbon masses down to 1 mg. Solid samples have almost no cross contamination during the measurement, whereas gas samples show a significant contamination from one sample to another which results in reduced precision. For this reason gas targets can be used where less precision is required (e.g. biomedical applications) or where only small samples are available (e.g. environmental investigations). Solid targets are produced where precise results are essential (e.g. archeological studies). We use gas targets for carbon masses from 1 to 100 μg and solid targets above 100 μg. The techniques to handle samples in the different mass regions for AMS measurements are described in the following.