Our objective is to place better constraints on the minor element composition of the solar wind (SW) through the analysis of Genesis solar wind collectors. Because the SW samples the solar photosphere, the composition of which is thought to represent that of the solar nebula (Bochsler, 2000), we will investigate how SW chemistry compares with current estimates of bulk Solar System (e.g., Lodders, 2003; Palme and Jones, 2003) and solar photospheric chemical abundances (e.g. Asplund et al., 2006). Na has not yet been successfully measured in Genesis spacecraft collector arrays, but it is predicted to have a sufficiently high fluence for accurate measurements to be obtained by secondary ion mass spectrometry (SIMS) (1.1e11; Burnett et al., 2003). Our goal is to use SIMS to measure the Na elemental abundance in the Genesis diamondlike carbon (DLC) collector wafers, which are the only conducting Geneses array-wafer type suited to Na analysis (A. Jurewicz, oral communication). Previous reconnaissance measurements of Na were limited by surface contamination on the Genesis collectors (Burnett et al., 2007; A. Jurewicz; oral communication). We believe we can address this analytical challenge by beginning our SIMS depth profile analysis on the backside of mechanically and chemically thinned collector wafers. Backside depth profiling has recently been developed for analysis of Genesis Si collectors (Heber et al. 2010) to reduce the contribution of surface particulate contamination, and permit the analysis crater surface to achieve steady state conditions with regard to the secondary ion yields. Exposing the back side of the thinned collector surface will also allow us to internally-standardize our SIMS analyses using reference implants. This cannot be done from the front, as there is only one stable isotope of Na. The fluences of Ca and Cr will also be investigated in order to cross-check the results of our approach with results from other laboratories (c.f., Veryovkin et al., 2010a, b). That Ca and Cr are estimated to have relatively high fluences in the Genesis bulk collector wafers (1.2e11 and 2.6e10 atoms/cm2 respectively; Burnett et al., 2003) should also facilitate high precision analyses.
|Effective start/end date||9/1/12 → 8/31/15|
- NASA: Goddard Space Flight Center: $89,385.00