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IMPROVING IONPLUS MICADAS PERFORMANCE WITH RECESSED GRAPHITE

Published online by Cambridge University Press:  04 April 2024

Taylor A B Broek Open the ORCID record for Taylor A B Broek [Opens in a new window]  and
Mark L Roberts
Taylor A B Broek*
Affiliation:
National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA, USA
Mark L Roberts
Affiliation:
National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA, USA
*
*Corresponding author. Email: taylor.broek@whoi.edu
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Abstract

Cathodes with recessed sample surfaces have several benefits in cesium sputter ion sources, including higher output, more efficient use of sample material, and improved focusing of the extracted ion beam. However, the Ionplus MICADAS uses cathodes with a graphite surface that is essentially flush with the sample holder. To evaluate the performance of recessed graphite with the MICADAS and determine the optimal surface depth, we tested four different depths, including the standard (flush) pressing method, 0.5 mm, 1.0 mm, and 1.5 mm. We found that recessed depths of 1.0 and 1.5 mm resulted in 20% higher ion beam current compared to the standard method under the same source conditions. The results are consistent with the beam produced from the recessed targets being more narrowly focused with a lower emittance, resulting in better transmission through the accelerator. Small graphite samples (200 µg C) with recessed surfaces produced higher currents for longer, leading to a 2–3× increase in sample ionization efficiency. Additionally, there was some evidence that isotopic ratio measurements of recessed samples were more stable over time. Overall, samples recessed to 1 mm depth offered numerous advantages over the standard pressing method and we have subsequently started pressing all MICADAS graphite using this approach.

Keywords

AMSradiocarbonMICADAS
Type
Conference Paper
Information
Radiocarbon , First View , pp. 1 - 9
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Copyright
© Woods Hole Oceanographic Institution, 2024. Published by Cambridge University Press on behalf of University of Arizona

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Footnotes

Selected Papers from the 24th Radiocarbon and 10th Radiocarbon & Archaeology International Conferences, Zurich, Switzerland, 11–16 Sept. 2022.

References

REFERENCES

Broek, TAB, Ognibene, TO, McFarlane, KJ, Moreland, KC, Brown, TA, Bench, G. 2021. Conversion of the LLNL CAMS 1 MV biological AMS system to a semi-automated natural abundance 14C spectrometer: system optimization and performance evaluation. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 499:124–132.CrossRefGoogle ScholarPubMed
Fallon, SJ, Guilderson, TP, Brown, TA. 2007. CAMS/LLNL ion source efficiency revisited. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 259:106–110.CrossRefGoogle Scholar
Gagnon, AR, McNichol, AP, Donoghue, JC, Stuart, DR, von Reden, K. 2000. The NOSAMS sample preparation laboratory in the next millennium: Progress after the WOCE program. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 172:409–415.CrossRefGoogle Scholar
Hlavenka, JD, Abrams, H, Roberts, ML, Longworth, BE. 2017. Increased AMS ion source efficiency and ion currents by modifying SNICS cathode material and geometry. Physics Procedia 90:17–21.CrossRefGoogle Scholar
Middleton, R. 1989. A negative ion cookbook [unpublished]. University of Pennsylvania.Google Scholar
Roberts, ML, Burton, JR, Elder, KL, Longworth, BE, McIntyre, CP, von Reden, KF, Han, BX, Rosenheim, BE, Jenkins, WJ, Galutschek, E, McNichol, AP. 2010. A high-performance 14C accelerator mass spectrometry system. Radiocarbon 52:228–235.CrossRefGoogle Scholar
Southon, J, Roberts, ML. 2000. Ten Years of Sourcery at CAMS/LLNL- Evolution of a Cs Ion Source. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 172:257–261.CrossRefGoogle Scholar
Synal, HA, Stocker, M, Suter, M. 2007. MICADAS: A new compact radiocarbon AMS system. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 259:7–13.CrossRefGoogle Scholar
Tiessen, C, Kieser, W, Zhao, X. 2021. Optimizing a cesium-sputter ion source using Lorentz 2E. 15th Conference on Accelerator Mass Spectrometry (AMS-15). Sydney, Australia.Google Scholar
Vogel, J. 2021. Potential ways to increase C– from CO2-fed sputter sources. 15th Conference on Accelerator Mass Spectrometry (AMS-15). Sydney, Australia.Google Scholar
Yokoyama, Y, Koizumi, M, Matsuzaki, H, Miyairi, Y, Ohkouchi, N. 2010. Developing ultra small-scale radiocarbon sample measurement at the University of Tokyo. Proceedings of the 20th International Radiocarbon Conference. Radiocarbon 52:310–318.CrossRefGoogle Scholar
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