Pushing the limits of 41Ca AMS with CaF2 targets at DREAMS

The performance of 41Ca measurements at the 6MV AMS system at HZDR, DREAMS (DREsden AMS) was improved in terms of overall efficiency and suppression of interfering isobar 41K. Mixing CaF2 samples not only with Ag, but also with PbF2 increases the negative ionization efficiency by a factor 3, from 0.15% to 0.45%. This option is dedicated to low level samples because ion source parameters have to be lowered, which increases the measurement time. In general, 41K–suppression factor of the detector is improved from 2 × 10⁴ to 4 × 10⁴ by advances in the analysis of the spectra. With such improvements, a 95%confidence level (C.L.) sensitivity for the 41Ca/40Ca ratio of 2 × 10–15 can be achieved at DREAMS.