41Ca measurements on the 1 MV AMS facility at the Centro Nacional de Aceleradores (CNA, Spain).

We present a detailed study of the performance parameters for 41 Ca measurements at the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) in Seville. Mixing CaF 2 with Ag, we get stable ( 40 CaF 3 ) − currents between 50 and 100 nA. Transmission of the 2+ state in the He stripper is 41%, while optical transmission in the HE sector is typically higher than 95%. At low energies we cannot separate 41 Ca from the isobar 41 K at the detector, but the interference is reduced by using ( 41 CaF 3 ) − ions. The remaining contribution is corrected by measurement of the other stable isotope of potassium, 39 K, to estimate this interference (K-correction). After this correction, we reach a 41 Ca/ 40 Ca background level between 5 × 10 −12 and 8 × 10 −12 , making possible measurements of 41 Ca/ 40 Ca ratios higher than 4 × 10 −11 . Intercomparisons with the 0.6 MV AMS system at ETH Zurich show a quite good correlation. [ABSTRACT FROM AUTHOR]