Seeing Shell Wall Fluctuations

Irregularities in ICF shells need to be characterized in detail. Outside and inside surface, and wall thickness fluctuations are all Raleigh-Taylor unstable and can cause a shell to fail during compression. Until recently we could only detect outside surface profile fluctuations, measured along three mutually perpendicular great circles and displayed as line graphs. Measurements, paths, and display have all been upgraded to improve our ability to see fluctuations. We have added a Wallmapper that can determine thickness along the same paths as the surface profiles. The thickness data can be subtracted from the outer surface profile to give a (low resolution) inner surface profile. We have measured the surface profiles along up to 8 paths, and have displayed these profiles wrapped around the image of a sphere. With sufficient paths, this format gives a sense of the 2-D surface fluctuations on the shell. These additions should help us to understand the nature of shell defects and optimize our production processes.