Study on presolar grain using multi-parameter coincidence spectroscopy method

We developed the multi-gamma ray activation analysis method, which is a highly sensitive and non-destructive elemental analysis due to the combination of the multi-gamma ray coincidence measurement with the neutron activation analysis. An anomalous concentration of iridium on the earth surface is an important clue to the meteorite flying, because the iridium content on the earth surface is much smaller than that in a meteorite. We succeeded to measure the iridium in 50-100 mg rock with 10 ppt detection limit. In this investigation, the elemental analysis of trace amounts was attempted on a presolar grain found in meteorites using this method. Consequently, eight kinds of elements were detected, the iridium isotope ratio in a nanodiamond being estimated. From these results, it may be expected that some information is obtained on several processes of elemental synthesis forming the solar system. (M.H.)