Speaker
Description
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 as 60Fe.
In this work, we stepped up the development of an accelerator mass spectrometry (AMS) method for detecting 60Fe 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 nuclide 60Fe. A 1 µm thick Si3N4 foil 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, an 60Fe sample with an abundance of 1.125 × 10-10 was used to test the new AMS system. The results indicate that 60Fe was clearly distinguished from the isobar 60Ni. The sensitivity was evaluated to be better than 4.3 × 10-14 based on the 5.8 hours blank sample measurements, and the sensitivity could in principle be expected to be about 2.5 × 10-15 when the data are accumulated for 100 hours which is feasible for future lunar sample measurements because the main contaminants were sufficiently separated.
