Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 2004 | public
Journal Article

A gas ion source for continuous-flow AMS

Abstract

The first gas-fed ion source for radiocarbon AMS applications (without sputtering) has been operated at the Woods Hole NOSAMS Facility. A three-year, off-line test program resulted in positive carbon ion currents up to 1 mA and negative ion currents up to 80 µA. Recently, the compact, permanent-magnet microwave plasma ion source and magnesium vapor charge-exchange canal were coupled to the recombinator injector of the 2.5 MV Tandetron. When the ion source was operated on CO_2 at a flow rate of about 200 µ1 per minute, negative carbon ion beams up to 20 µA were obtained, at an energy of 35 keV. Radiocarbon measurements were performed on standard reference gases and the dynamic response to square-wave pulses of gas was determined. Time constants in the ion source are less than 1 s, which should allow analysis of chromatographic peaks of CO_2 with very little broadening. A combustion device has been constructed to generate CO_2 for direct injection into the source. Argon carrier gas is used to buffer the pressure at one atmosphere in the sample gas injector. A dedicated ion-beam injector, with higher angular acceptance and higher transmitted currents, is being constructed for the AMS system.

Additional Information

© 2004 Elsevier B.V. Gas samples were supplied by the Sample Preparation Laboratory at NOSAMS. We thank the University of Toronto, for loaning us the compact microwave plasma ion source, originally built at the Chalk River Laboratories of Atomic Energy of Canada Limited and also for the loan of a large ion implanter magnet, which was used as part of the test stand. We thank Diamond Semiconductor Group (Gloucester,MA) for the loan of a 40kV power supply. This work has been supported in part by a National Science Foundation Cooperative Agreement, OCE-9807266.

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023