New Approaches to the Preparation of PαMS Beads as Mandrels for NIF-Scale Target Capsules

We report on a new method using heated density gradient columns for preparing spherical poly(α-methylstyrene) (PαMS) bead mandrels for inertial confinement fusion spherical shell targets. Using 1,2 propane diol/glycerol mixtures, stable density gradient columns for supporting PαMS beads can be prepared at temperatures as high as 150 °C. At these temperatures plasticized commercial beads become fluid and spherical, however loss of the plasticizer and very low molecular weight components of the bead due to limited solubility in the column fluid leads to surface finish problems. We also present results on PαMS beads prepared in an aqueous bath batch mode. Using these techniques beads with maximum out-of-rounds less than 5 μm have been produced.