The isotopic composition of Gd in one chondrite, two achondrites, and the silicate inclusions of two iron meteorites has been determined. When corrected for mass discrimination, Gd in all samples except the Norton County achondrite shows the same relative isotopic abundances as terrestrial Gd. These results set an
Analysis of the Genesis samples is underway. Preliminary elemental abundances based on Genesis sample analyses are in good agreement with in situ-measured elemental abundances made by ACE/SWICS during the Genesis collection period. Comparison of these abundances with those of earlier solar cycles indicates that the solar wind composition is relatively stable between cycles for a given type of flow. ACE/SWICS measurements for the Genesis collection period also show a continuum in compositional variation as a function of velocity for the quasi-stationary flow that defies the simple binning of samples into their sources of coronal hole (CH) and interstream (IS).
An amorphous diamond-like carbon film deposited on silicon made at Sandia National Laboratory by pulsed laser deposition was one of several solar wind (SW) collectors used by the Genesis Mission (NASA Discovery Class Mission #5). The film was *1 lm thick, amorphous, anhydrous, and had a high ratio of sp 3 -sp 2 bonds ([50%). For 27 months of exposure to space at the first Lagrange point, the collectors were passively irradiated with SW (H fluence *2 9 10 16 ions cm -2 ; He fluence *8 9 10 14 ions cm -2 ). The radiation damage caused by the implanted H ions peaked at 12-14 nm below the surface of the film and that of He about 20-23 nm. To enable quantitative measurement of the SW fluences by secondary ion mass spectroscopy, minor isotopes of Mg ( 25 Mg and 26 Mg) were commercially implanted into flight-spare collectors at 75 keV and a fluence of 1 9 10 14 ions cm -2 . The shapes of analytical depth profiles, the rate at which the profiles were sputtered by a given beam current, and the intensity of ion yields are used to characterize the structure of the material in small areas (*200 9 200 ± 50 lm). Data were consistent with the hypothesis that minor structural changes in the film were induced by SW exposure.
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