Advances in Handling Small Radiocarbon Samples at the Laboratoire de Mesure du Carbone 14 in Saclay, France

Abstract

The Artemis accelerator mass spectrometry (AMS) facility, installed in 2003 in Saclay, France, is devoted to radiocarbon measurements. Samples are submitted by scientists in the fields of Quaternary geology, environmental sciences, and archaeology. The entire preparation process, originally optimized for samples with about 1 mg of carbon, has been tested in recent years for samples with a lower carbon content. In particular, we prepared and measured carbonate and organic background and reference samples ranging in mass from 0.01 to 1 mg C. These tests helped define our protocol's practical limits and determine necessary improvements. Furthermore, our experiments demonstrated that satisfactory graphitization yields (80% and higher) and low background values can be obtained with samples down to 0.2 mg of carbon. For handling smaller samples, we developed a specific process. We tested smaller reactors (5 mL in volume) and adapted the reduction parameters (H2 pressure and temperature) accordingly. We also tested the effect of a chemical water trap on graphitization yields and 14C results. This paper presents in detail the aforementioned developments and reports the 14C results obtained for background and standard small samples prepared with the modified reactors.