9305201 Hervig The secondary ion mass spectrometer (SIMS or ion microprobe) at Arizona State University will be modified to improve the performance of the primary ion beam (smaller diameter and, hence, better analytical spatial resolution). A better vacuum will also be achieved, resulting in a lowering of detection limits, especially for light volatile elements. The instrument modifications will be designed, built and tested in-house by the Principal Investigator and colleagues. The improved ASU ion microprobe will be available to on-campus and off-campus researchers, and will be used primarily in earth sciences projects to determine isotope and trace element compositions of geological and meteorite samples with a spatial resolution on the order of several micrometers. ***