Carbonate as sputter target material for rapid 14C AMS
Carbonate as sputter target material for rapid 14C AMS
Date
2012-04-17
Authors
Longworth, Brett E.
Robinson, Laura F.
Roberts, Mark L.
Beaupre, Steven R.
Burke, Andrea
Jenkins, William J.
Robinson, Laura F.
Roberts, Mark L.
Beaupre, Steven R.
Burke, Andrea
Jenkins, William J.
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Abstract
This paper describes a technique for measuring the 14C content of carbonate samples by
producing C-ions directly in the negative ion sputter source of an accelerator mass
spectrometer (AMS) system. This direct analysis of carbonate material eliminates the
time and expense of graphite preparation. Powdered carbonate is mixed with titanium
powder, loaded into a target cartridge, and compressed. Beam currents for optimally sized carbonate targets (0.09-0.15 mg C) are typically 10-20% of those produced by
optimally-sized graphite targets (0.5-1 mg C). Modern (>0.8 Fm) samples run by this
method have standard deviations of 0.009 Fm or less, and near-modern samples run as
unknowns agree with values from traditional hydrolysis/graphite to better than 2%.
Targets with as little as 0.06 mg carbonate produce useable ion currents and results, albeit
with increased error and larger blank. In its current state, direct sputtering is best applied
to problems where a large number of analyses with lower precision are required. These
applications could include age surveys of deep-sea corals for determination of historic
population dynamics, to identify samples that would benefit from high precision analysis,
and for growth rate studies of organisms forming carbonate skeletons.
Description
Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 294 (2013): 328-334, doi:10.1016/j.nimb.2012.05.014.