Search

AbstractAll planned National Ignition Facility (NIF) capsule targets except machined beryllium require a glow discharge polymer (GDP) mandrel upon which the ablator is applied. This mandrel, ~2 mm in diameter, must at least meet if not exceed the symmetry and surface finish requirements of the final capsule. Such mandrels are currently produced by the three-step depolymerizable mandrel technique. The quality of the final mandrel depends upon precise optimization and execution of each of the three steps. We had shown previously that fabrication of a mandrel which met the symmetry and surface finish requirements was feasible using this technique. In this paper we will discuss recent progress towards converting this process into a high yield, production scale process.

We determined the intra-individual biological variability of plasma homocysteine in 20 healthy subjects. The intra-individual coefficient of variation was relatively low (8·3%), indicating that a single measurement can be used to characterize the average homocysteine concentration. A population study measuring plasma homocysteine and serum folate levels was conducted on serum samples collected from 1109 randomly selected, fasting adults with a wide age range. We determined age- and gender-specific central 0·95 intervals and found that subjects in the highest quartile of serum folate had significantly lower (P= 0·0001) mean plasma homocysteine concentrations than did those in the lowest quartile of folate values. An ‘ideal’ homocysteine reference range, based on targeting those subjects who are likely to be folate replete, is preferable to the population-based range using the central 0·95 interval.

AbstractAn improved process for production of ICF Target Mandrels has been developed. Shells made from PAMS (poly-α-methylstyrene) are coated with GDP (glow discharge polymer). The PAMS is then removed by depolymerization and volatilization at 300°C, leaving a GDP mandrel. Compared to past polymer mandrels, this process yields GDP mandrels with significant improvements in wall thickness control, sphericity and concentricity, and the complete absence of vacuoles. The process is capable of making GDP shells with a wide size range (from 300 < o.d. < 2700 µm), and an independently controlled wall thickness (from 1 to 30 µm). The GDP can be doped with a variety of elements.

Natural abundance 13C NMR experiments using cross polarization and magic angle spinning provide a unique method for monitoring the doping of polyacetylene. In contrast with previous authors we find that the doping of cis-polyacetylene with AsF5 leads, even at low doping levels, to a new signal characteristic of the doped regions of the polymer. Similar measurements on trans-polyacetylene indicate that the doping of the trans isomer proceeds considerably more uniformly than that of the cis isomer. Comparisons with appropriate model compounds suggest that the observed shift of the 13C NMR signal on doping is primarily a chemical shift rather than a Knight shift. Finally we discuss recent results on the nature of proton acid doping of polyacetylene, a process which shows remarkable similarities to oxidative doping.