LASER FUSION TARGET SHELL WALL THICKNESS FROM INTERFERENCE FRINGE SHAPE-ANALYSIS

We have developed an analytic expression to describe the shape of inte rference fringes produced by transparent shells using plane-wave front dual-beam interferometry. Using this expression, one can calculate th e wall thickness of the shell from a few simple measurements of the cu rvature or separation of fringes relative to its size. ft is feasible to calculate wall thickness to within a few percent, the limit being t he ability to accurately locate the center of the interference fringes . One of our approaches has been incorporated into an image analysis p rogram. We will discuss the usefulness of this approach as a first ste p toward an automated image analysis program.