  To meet the measurement demands on small-mass radiocarbon (carbon content at
10-6g level) which are becoming increasingly significant. Xi'an-AMS has made
improvement to the existing method of sample loading and has upgraded the Cs
sputter ion source from the original SO-110 model. In order to study the
feasibility of small-mass samples in Xi'an-AMS and evaluate the radiocarbon
sample preparation ability using existing routine systems of H2/Fe and Zn/Fe,
the small-mass samples prepared by four different methods are tested. They are
mass division method, mass dilution method, H2/Fe reduction method and Zn/Fe
reduction method. The results show that carbon mass above 25ug can be prepared
using the existing Zn/Fe system, but no less than 100ug is required using the
existing H2/Fe system, which can be improved. This indicates Xi'an-AMS are now
able to analyze small-mass radiocarbon samples.
