In-situ cosmogenic 14C analysis at ETH Zürich: Characterization and performance of a new extraction system

Abstract

We present a new in-situ cosmogenic 14C extraction system developed at ETH Zürich. This system quantitatively extracts 14C produced in quartz by cosmic rays using a high temperature extraction procedure. A key improvement of the new extraction system is the implementation of largely automated sequences, CO2 transport in a He flow and the addition of a “dead” CO2 carrier gas, which ensure highly reproducible operation while limiting the required operator attendance. Intercomparison quartz samples were routinely measured over a year of operation and yield 14C concentrations of 7.27 (±0.03) · 105 at/g quartz for CRONUS-A (n = 7) and 1.24 (±0.17) · 104 at/g quartz for CRONUS-N (n = 4). The excellent performance of the new system is highlighted by low procedural blanks of ca. 3 · 104 14C atoms and coefficients of variation for the CRONUS-A and CRONUS-N analyses of only 0.4% and 14% respectively.