Preparing and measuring ultra-small radiocarbon samples with the ARTEMIS AMS facility in Saclay, France

Abstract

The ARTEMIS facility in Saclay France measures, on average, 4500 samples a year for French organizations working in an array of fields, including environmental sciences, archeology and hydrology. In response to an increasing demand for the isolation of specific soil compounds and organic water fractions, we were motivated to evaluate our ability to reduce microgram samples using our standard graphitization lines and to measure the graphite thus obtained with our 3MV NEC Pelletron AMS. Our reduction facility consists of two fully automated graphitization lines. Each line has 12 reduction reactors with a reduction volume of 18ml for the first line and 12ml for the second. Under routine conditions, we determined that we could reduce the samples down to 10μg of carbon, even if the graphitization yield is consequently affected by the lower sample mass. Our results when testing different Fe/C ratios suggest that an amount of 1.5mg of Fe powder was ideal (instead of lower amounts of catalyst) to prevent the sample from deteriorating too quickly under the Cs+ beam, and to facilitate pressing procedures. Several sets of microsamples produced from HOxI standard, international references and backgrounds were measured. When measuring 14C-free wood charcoal and HOxI samples we determined that our modern and dead blanks, due to the various preparation steps, were of 1.1±0.8 and 0.2±0.1μg, respectively. The results presented here were obtained for IAEA-C1, 14C-free wood, IAEA-C6, IAEA-C2 and FIRI C.