Each stage in the handling of radiocarbon samples provides an additional opportunity for contamination and increased cost. For large samples, graphitization is worthwhile since it allows precise AMS measurements to be made in a short time. Some samples, however, do not require high precision. These include small samples, for which high precision is impossible, and samples for which only an approximate date is required. In these cases, there is an advantage in burning the samples and then introducing the CO2 directly into a gas ion source. ORAU has developed a system for performing on-line combustion, which is being tested for routine use. This paper presents the performance characteristics and explains the main design features. Such systems are expected to be useful for small samples in radiocarbon dating, the pre-screening of radiocarbon ages and in biomedical applications. The hybrid (graphite and CO2) ion source at Oxford has also been upgraded to incorporate a 40-target sample changing mechanism. This can be used both for graphite samples and for the targets required for measurements on CO2. (C) 2000 Elsevier Science B.V. All rights reserved.
