9615982 Hervig This grant provides $95,210 as partial support of the costs of acquiring a normal incidence electron gun (NIEG)for the Cameca 3f secondary ion mass spectrometer (SIMS) at Arizona State. This accessory compensates for charge buildup that occurs on the surface of samples that are being sputtered with positively charged ion beams of alkali metals (i.e. Cs+), such as is necessary to analyze for oxygen isotopes and other electronegative elements (i.e., H, C, F, Cl, P, S, As, Sb, Se). The beam-normal geometry of this electron gun allows for analysis of samples that are prone to damage from intense electron bombardment that occurs using an oblique angle electron gun that was designed in-house. Addition of this accessory will allow an increase in the precision (to ca. 1 per mil)and perhaps in the lateral resolution of oxygen isotopic SIMS analyses of insulator phases and thus will provide for nearly a factor of two increase in the precision of their currently configured SIMS. The increase in precision affordable with the addition of a normal incidence electron gun will undoubtedly be used fruitfully by this PI in his continued studies of the early diagenesis of authigenic clay minerals, volatile element budgets in magmas based on Sulfur isotopic analyses of melt inclusions in volcanic rocks and mapping of volatile trace element abundances in environmental samples. ***
