This award provides one-half the funds needed to acquire a mass spectrometer that will be installed and operated in the Division of Geological and Planetary Sciences at the California Institute of Technology. The mass spectrometer will be of a novel design combining a standard magnetic sector mass filter with a second stage electric quadrupole mass filter in order to achieve maximum sensitivity for isotope ratio analysis. The Caltech group acquiring this instrument have been involved in design its prototype specifically to carry out analysis of thorium 232/230 isotope ratios where the abundant 232 isotope normally masks the presence of thorium 230 unless the ratio is measured on an instrument capable of ultra high- sensitivity. The thorium 232/230 measurement is especially useful for dating natural materials in the age range 10,000 to 1,000,000 years before present.
