Continuous Radiocarbon Records by Laser Ablation – Status Report

The unique laser ablation (LA) setup at ETH Zurich (Switzerland), coupled to a MICADAS accelerator mass spectrometer (AMS), enables rapid ¹⁴C analyses and has been successfully employed for a broad range of carbonate archives such as stalagmites (Welte et al., 2021), otoliths (Andrews et al., 2019), and shells of Arctica islandica. An 193 nm ArF excimer laser is used to liberate CO and CO₂ from the sample surface by ablation. The gas is then flushed with helium into the gas ion source of the AMS for online measurement.

Advantages of the novel techniques are a significant reduction in labour-intensive sample preparation and the speed of measurement, which minimises the expensive beam-time of the AMS. However, as a transient signal is measured where each sampling location is only measured for a short duration, uncertainties associated with LA-AMS are significantly higher than for conventional measurement techniques. Still, it is possible to locate strong signals such as a growth stop or the bomb spike very rapidly and precisely using only two scans of the sample. Here we present the status of the setup and progress on data reduction aimed at reducing the larger uncertainties. Preliminary results from comparisons of parallel tracks on a stalagmite allow testing the data reduction strategy and will be shown.

Andrews, A. et al. (2019), Marine and Freshwater Research, https://doi.org/10.1071/mf18265

Welte, C. et al. (2021), Climate of the Past, 17(5), 2165–2177, https://doi.org/10.5194/cp-17-2165-2021