The 17th International Symposium on Origin of Matter and Evolution of Galaxies

The Moon provides a unique environment for investigations of nearby astrophysical events such as supernovae. Lunar samples retain valuable information provided by these nearby astrophysical events, via detectable long-lived "fingerprint" radionuclides such as⁶⁰Fe.

In this work, we stepped up the development of an accelerator mass spectrometry (AMS) method for detecting⁶⁰Fe using the HI-13 tandem accelerator at the China Institute of Atomic Energy. Since interferences could not be sufficiently removed with the existing magnetic systems of the tandem accelerator and the following Q3D magnetic spectrograph, a Wien filter with a maximum voltage of ±60 kV and a maximum magnetic field of 0.3 T was installed after the accelerator magnetic systems to lower the detection background for the low abundance nuclide⁶⁰Fe. A 1 µm thick Si₃N₄foil was installed in front of the Q3D as an energy degrader. For particle detection, a multi-anode gas ionization chamber was mounted at the center of the focal plane of the spectrograph. Finally, an⁶⁰Fe sample with an abundance of 1.125 × 10^-10was used to test the new AMS system. The results indicate that⁶⁰Fe was clearly distinguished from the isobar⁶⁰Ni. The sensitivity was evaluated to be better than 4.3 × 10^-14based on the 5.8 hours blank sample measurements, and the sensitivity could in principle be expected to be about 2.5 × 10^-15when the data are accumulated for 100 hours which is feasible for future lunar sample measurements because the main contaminants were sufficiently separated.