AN UPDATE ON THE PERFORMANCE OF THE IN SITU¹⁴C EXTRACTION LINE AT THE UNIVERSITY OF BERN

Abstract

We present the current performance of the in situ radiocarbon (14C) extraction line at the University of Bern with an improved extraction and combustion system. After three major steps of improvement, the extraction of sample CO2 gas now takes place inside a platinum crucible, supported by an outer quartz-glass crucible. This setup allows us to operate the line as a closed system for several samples without breaking the vacuum. Measurements of procedural blanks and samples from our reference strewn field, Jiddat al Harasis 073, performed in our system all show a good reproducibility and, for the strewn field samples, consistency with published data. We describe each improvement step in detail, discussing the advantages and disadvantages of all tested setups. By sharing our knowledge, we aim to inform and prevent others from making the same or similar detours in establishing 14C extraction systems for extraterrestrial samples.

Terrestrial ages of seven meteorite strewn fields and two single unpaired meteorites from the Sultanate of Oman determined using 14C and 10Be

“…Some of the results were previously discussed by Sliz et al. (2020). The major finding is that the reproducibility of the measurements is satisfactory.…”

“…For estimating the reproducibility of the 14 C extraction procedure, Sliz et al. (2020) used a homogenized ground sample from the L6 chondrite JaH 073. Based on four replicate measurements, they found a resultant 1σ standard deviation of 2.0 × 10 6 atoms 14 C per g, which is 7.8%.…”

“…We therefore added a systematic uncertainty of ±7.8% to the measured 14 C atoms per gram of meteorite. We assume that this approach is valid for meteorites with terrestrial ages in the range 0–20 ka, that is, for specific 14 C activity concentrations in the range (20–70) × 10 6 atoms per g. Note that the repeated analysis of the JaH 073 samples (in total seven) cannot be used to determine the external reproducibility because the extraction protocols varied: (i) extraction using a convection oven (JaH073_018 and JaH073_019; Mészáros et al., 2018), (ii) extraction using an RF generator and Fe pellets as “combustion catalysts” (JaH073_5; Sliz et al., 2020), and (iii) extraction using an RF generator and Pt‐crucible as the heat medium via induction heating (JaH073_012, JaH073_013, JaH073_016, JaH073_017; Table S1) (Sliz et al., 2020). Hence, the reproducibility estimate is based only on the replicates measured using the updated extraction protocol.…”

“…The 14 C extraction line at the University of Bern (Mészáros et al, 2018;Sliz et al, 2018Sliz et al, , 2020 has been built to determine terrestrial ages of meteorites. Doing so, the 14 C activity concentrations are measured in Bern and the 10 Be activity concentrations are measured at CEREGE (Aix-en-Provence, France; Arnold et al, 2010Arnold et al, , 2013.…”

“…Currently, many of the meteorites found in the Sultanate of Oman are studied by our group (Mészáros et al., 2018; Sliz et al., 2018, 2019, 2020), particularly with respect to the terrestrial ages, by using the cosmogenic radionuclide 14 C. Note that the systematic investigation of terrestrial ages of meteorites is crucial for studying the time scale of meteorite accumulation (Jull, 2006), effects of erosion on the meteorite population on Earth (Al‐Kathiri et al., 2005; Hutzler et al., 2016; Jull et al., 1993; Pourkhorsandi et al., 2019; Zurfluh et al., 2016), and most importantly for studying the meteorite flux over time (Bland et al., 1996; Halliday et al., 1989). The 14 C terrestrial age dating is a well‐established technique with an immense potential but is currently applied to meteorites only in very few laboratories worldwide (Jull et al., 2013; Mészáros et al., 2018; Minami & Nakamura, 2001; Minami et al., 2006; Sliz et al., 2020).…”