Development of an automatic gas handling system for microscale AMS 14C measurements

A gas handling technique has been developed for metering CO2 into the gas ion source of the Erlangen AMS facility. Further investigations and developments have resulted in a system that enables the handling of gaseous samples with carbon masses from 1 μg to 1 mg. The system has been optimized for coupling an elemental analyzer to a gas ion source. Moreover, the system can be connected to any other system that produces CO2, e.g. gas ampoules, gas chromatographs, etc. The principle of the gas handling system is to first store and isolate CO2 cryogenically. Then the CO2 is fed into the ion source by the pressure difference between the CO2 reservoir and the gas ion source which are connected by a glass capillary. By regulation of the CO2 pressure, the CO2 flow into the ion source can be controlled. The outstanding advantage of this easy technique is the possibility of its complete automation. For use of the system with an elemental analyzer we created application software that controls the combustion of the sample, the cryogenic storage and the exact metering of the CO2 into the ion source. Besides the application of using CO2 for radiocarbon dating, our gas handling system opens new possibilities of research in fields where only small samples are available or large series of samples have to be measured quickly, e.g. environmental or biomedical research. In addition this system has turned out to be a perfect tool for detailed investigations of gas ion sources.