Optimization of the LLNL/CAMS gas-accepting ion source and 1 MV compact AMS for natural abundance radiocarbon analysis of CO2

TitleOptimization of the LLNL/CAMS gas-accepting ion source and 1 MV compact AMS for natural abundance radiocarbon analysis of CO2
Publication TypeJournal Article
Year of Publication2022
AuthorsBroek, TAB, Moreland, KC, Ognibene, TJ, McFarlane, KJ, Brown, TA
JournalNuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Volume530
Pagination1–7
Date Published11/2022
ISSN0168-583X
KeywordsAccelerator mass spectrometry, CO, Gas-accepting ion source, radiocarbon
Abstract

The Lawrence Livermore National Laboratory – Center for Accelerator Mass Spectrometry (LLNL/CAMS) 1 MV AMS system was converted from a biomedical AMS instrument to a natural abundance 14C spectrometer. The system is equipped with a gas-accepting hybrid ion source capable of measuring both solid (graphite) and gaseous (CO2) samples. Here we describe a series of experiments intended to establish and optimize 14CO2 measurement capabilities at natural abundance levels. A maximum instantaneous ionization efficiency of 8 % was achieved with 3 % CO2 in helium at a flow rate of approximately 220 µL/min (3.5 µg C/min). For modern materials (e.g., OX I) we measured an average of 240 ± 50 14C counts/µg C, equivalent to a total system efficiency of approximately 3 %. Experimental CO2 samples with F14C values ranging from 0.20 to 1.05 measured as both graphite and directly as CO2 gas produced equivalent values with an average offset of < 2σ.

URLhttps://www.sciencedirect.com/science/article/pii/S0168583X22002178
DOI10.1016/j.nimb.2022.08.012