SOLAR WIND KRYPTON IN POLISHED ALUMINUM GENESIS COLLECTOR: CURRENT STATUS.

Introduction: One of the major Genesis Mission goals is to verify solar wind composition previously estimated from analysis of solar-wind-rich lunar and meteoritic materials [e. g., 1, 2, 3]. The difference, if observed, may constrain a temporal variation of solar wind isotopic composition. The heavy noble gases, Kr and Xe, are special because they have multiple isotopes spanning over ten mass units, so they can be used as indicators of nonlinear fractionation. Here we present isotopic composition of krypton extracted from Polished Aluminum Genesis solar wind collector. Experimental: Presently our major difficulty measuring the heavy noble gas in the solar wind is impurities in the Genesis collectors which constitutes up to a half of the amount of collected solar wind. To solve this problem we first attempted to separate surface blank from deeply implanted solar wind noble gases using stepped power UV-laser extraction. Although this approach was very productive for light noble gases, it was not for Xe and Kr. Our Xe, Kr blanks turned out to be neither sufficiently reproducible nor linearly proportional to the raster area. Therefore, in this work we extracted all of the solar wind noble gases in one single step, with surface correlated gases being removed by 3-week 150°C baking followed by several low power defocused UV rastering of the entire collector. Our latest design of the extraction cell solves our earlier problem of sputtered Al condensation on the vacuum viewport. The collector is placed at 45° relative to incident laser beam and an additional 45° dichroic mirror is installed outside of the extraction cell to keep working distance constant (Fig. 1a,b). The long-focusing laser objective required for this arrangement has the benefit of a larger “depth of field”, which solves our earlier focus problems on the slightly curved polished aluminum collector (PAC).