Abstract The cosmogenic isotope 41Ca with a half-life of 99,000 years can, in principle, serve as a tracer for environmental processes at an age scale beyond the reach of 14C. With accelerator mass spectrometry, the ratio of 41Ca/Ca has been measured down to the 10−15 level in natural samples. A wide range of potential applications, such as the burial dating of bones and exposure dating of rocks, require measuring even smaller 41Ca/Ca ratios in the range of 10−16 to 10−15.
