Analysis of regular and small samples at Tandem Laboratory, Uppsala University: 10 years of operation using a MICADAS

We report on 10 years of operation of a MICADAS compact tandem accelerator for radiocarbon ( 14 C) analysis at the Tandem Laboratory national research infrastructure at Uppsala University comprising analysis of over 40,000 samples. Based on the large number of analyzed samples and associated references, we perform an analysis of the target scatter of employed IAEA-C7 and SRM-4990C-standards. As a result, we show how the target scatter deduced from a single magazine run is falling below the long-term statistical average, which can result in a systematic uncertainty in 14 C results obtained from such runs. We also discuss effects of sample size on current and potential corrections for contamination or non-linearities in the measurement for standard samples spanning a wide range of activity levels, down to below 10 µg C equivalent. Finally, we discuss an observed mass dependence of stable isotope ratios in IRMS, which, if not measured by the accelerator itself, could impact 14 C determination.