Improvements in the measurement of small 14CO2 samples at CologneAMS

Abstract Since 2015, the CologneAMS started operating a second SO-110 B ion source (Arnold et al., 2010; Klein and Mous, 2017) from High Voltage Engineering Europe (HVE) with a gas injection system (GIS) from Ionplus AG (Wacker et al., 2013) for the measurement of gaseous CO 2 samples. Significant effort was spent increasing the efficiency of C - ion beam extraction as well as the operational reliability. Details are described in Stolz et al. (2017). Recent work was aimed at prolonging the cleaning intervals and allowing unattended routine 14 CO 2 measurements. Problems related to sparking inside the source chamber could be eliminated by electrically shielding the ceramic linear actuator that is used to move the target pieces into the source head. Furthermore, the Cs reservoir temperature was decreased from 135 °C to 120 °C. The negative ion formation efficiency has dropped only slightly to about 5% with the current settings. Additionally, the GIS sample magazine capacity was doubled to 16 ampules, which enables longer measurements without user interaction. A dedicated software (Gas Injection Control Software, GICS) was developed that controls GIS and AMS hardware for fully autonomous measurements, including the source and accelerator startup, sample cracking or combustion, sample mixing with the He carrier gas and the transfer to the source, as well as the subsequent data analysis. This tool also comprises error detection routines in order to minimize the risk of losing a sample due to hardware failures. The blank value was reduced from typically 7 · 10 - 15 to ∼ 3 · 10 - 15 . This was achieved by modifications in the cleaning and measurement procedures. Recently a EuroVector EA3000 elemental analyzer (EA) was coupled to the GIS and integrated into the GICS software. First EA test measurements with standards, blanks and tree rings were performed as well as first automated overnight measurements with ampules and EA samples.