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Minimising 12 C 3+ interference on 4 He + measurements in a noble gas mass spectrometer

Schwanethal, J; (2015) Minimising 12 C 3+ interference on 4 He + measurements in a noble gas mass spectrometer. Journal of Analytical Atomic Spectrometry , 30 (6) pp. 1400-1404. 10.1039/C4JA00422A. Green open access

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Abstract

Measurements of helium isotopes used for geochronological studies are subject to interferences from 12C3+ and HD+. The 12C3+ interference was studied on a Nu Instruments Noblesse mass spectrometer which has sufficient mass resolution to measure the interference on the 4He+ peak due to 12C3+ directly, by setting the magnet at the relevant peak shoulders. Helium sensitivity varies with source trap current. Increasing the source trap current increases the electron fluence, and hence the probability of ionisation, within the source. The source trap current on the Noblesse is typically held at ∼400 μA. Increasing the trap current to 550 μA increases sensitivity to 4He+ approximately two-fold, but 12C3+ increases approximately 17 times. The 4He+ and 12C3+ peak shoulders at m/z = 4 are narrow, despite the high mass resolution, and consequently any instrument drift can cause the peak positions to be lost. However, it is shown that measurement of 12C2+ at m/z = 6 can be used to correct for this interference, allowing the intensity of the broad flat top of m/z = 4 to be used.

Type: Article
Title: Minimising 12 C 3+ interference on 4 He + measurements in a noble gas mass spectrometer
Open access status: An open access version is available from UCL Discovery
DOI: 10.1039/C4JA00422A
Publisher version: http://dx.doi.org/10.1039/C4JA00422A
Language: English
Additional information: This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1464571
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