Optimization of 18O measurement using NRA for studies of isotopic content in fossil meteorites

In this work, we discuss the possibility of a new approach to measuring oxygen isotope ratios in fossil meteorite samples, specifically one based on nuclear reaction analysis (NRA). Variations of oxygen ratios within meteoritic chromite grains can help to determine the type of meteorite to which the grains originally belonged. In this work, we have evaluated the possibility to use the reaction 18O(p, α)15N just above the 846 keV resonance to estimate the relative oxygen-18 content in a number of test samples. Another technique has to be employed for oxygen-16 measurements. A large area segmented silicon detector is used to detect the produced α particles. Results of the experimental 18O measurements for a number of samples including four extraterrestrial chromite grains are presented and compared with SIMNRA simulations. The advantage of a segmented silicon detector in the form of inherent pile-up suppression can be clearly seen in the current work.