Targets for low-adiabat direct-drive-implosion experiments on OMEGA must meet rigorous specifications and tight tolerances on the diameter,wall thickness,wall-thickness uniformity,and presence of surface features.Of t...Targets for low-adiabat direct-drive-implosion experiments on OMEGA must meet rigorous specifications and tight tolerances on the diameter,wall thickness,wall-thickness uniformity,and presence of surface features.Of these,restrictions on the size and number of defects(bumps and depressions)on the surface are the most challenging.The properties of targets that are made using vapor-deposition and solution-based microencapsulation techniques are reviewed.Targets were characterized using confocal microscopy,bright-and dark-field microscopy,atomic force microscopy,electron microscopy,and interferometry.Each technique has merits and limitations,and a combination of these techniques is necessary to adequately characterize a target.The main limitation with the glow-discharge polymerization(GDP)method for making targets is that it produces hundreds of domes with a lateral dimension of 0.7-2 μm.Polishing these targets reduces the size of some but not all domes,but it adds scratches and grooves to the surface.Solution-made polystyrene shells lack the dome features of GDP targets but have hundreds of submicrometer-size voids throughout the wall of the target;a few of these voids can be as large as~12 μm at the surface.展开更多
基金This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944the University of Rochester,and the New York State Energy Research and Development Authority.
文摘Targets for low-adiabat direct-drive-implosion experiments on OMEGA must meet rigorous specifications and tight tolerances on the diameter,wall thickness,wall-thickness uniformity,and presence of surface features.Of these,restrictions on the size and number of defects(bumps and depressions)on the surface are the most challenging.The properties of targets that are made using vapor-deposition and solution-based microencapsulation techniques are reviewed.Targets were characterized using confocal microscopy,bright-and dark-field microscopy,atomic force microscopy,electron microscopy,and interferometry.Each technique has merits and limitations,and a combination of these techniques is necessary to adequately characterize a target.The main limitation with the glow-discharge polymerization(GDP)method for making targets is that it produces hundreds of domes with a lateral dimension of 0.7-2 μm.Polishing these targets reduces the size of some but not all domes,but it adds scratches and grooves to the surface.Solution-made polystyrene shells lack the dome features of GDP targets but have hundreds of submicrometer-size voids throughout the wall of the target;a few of these voids can be as large as~12 μm at the surface.
