Cooling-induced deformation of polystyrene spherical shells

We carried out experiments on cooling-induced deformation (CID) of inertial -fusion fuel capsules. Polystyrene spherical shells were used as test sampl es. in the experiments, approximately 90 shells were cooled using liquid ni trogen and observed with an optical microscope. Pictures of each shell were recorded at 0 degrees C and -190 degrees C. and they were compared with ea ch other. About a half of the tested shells showed CID, where the maximum d eformation was in the order of 1% of the shell radius. Although the polysty rene shells were fabricated by a density-matched emulsion method using both hand-shaken microencapsulation and triple-orifice droplet-generator techni ques, we recognized no significant difference in deformation characteristic s between these two techniques. The observed CTD showed poor reproducibilit y. We tried annealing in order to prevent CID, but no apparent improvement was recognized.