Funding is requested to acquire a mass spectrometer to be installed at the Scripps Institution of Oceanography. The spectrometer is to be dedicated to the analysis of the isotopes of neon and nitrogen, volatile species whose isotopic signatures in basalts, mantle-derived xenoliths, diamonds, ocean waters, stratospheric air, and polar ice cores are significant in the interpretation of the geochemical history of the Earth's mantle and the evolution of the crust, oceans and atmosphere. The proposed mass spectrometer uses a novel system of switching ion beams on its collectors to achieve essentially simultaneous triple collection for either masses 20, 21 and 22 (neon) or 28, 29 and 30 (nitrogen) to make possible the analysis of very small samples containing low concentrations of these isotopes.
