Atom trap trace analysis of Ca-41 samples at 10^-16 abundance level

Calcium is one of the most important metals that migrates easily between major geochemical reservoirs at the Earth’s surface: hydrosphere, biosphere and the crust. ⁴¹Ca, as a trace radioisotope with a half-life of 99.4 kyr, has the natural abundance from 3×10^-15 to 2×10^-14 on Earth’s surface. On the abundance level of 10^-16, the most sensitive accelerator mass spectrometry(AMS) had the abundance measurement uncertainty of ~100%. In this work, we present an atom trap trace analysis (ATTA) method for 41Ca abundance measurement on the level of 10^-16 with ~10% uncertainty.

With ATTA, we demonstrate ⁴¹Ca abundance measurements of granites from Tibetan Plateau, modern goat and cod bones, and ancient bone fragments. Our development of ATTA paves the way of dating calcium-containing samples of middle and late Pleistocene in geoscience and archeology.