Preparation of Hollow Shell ICF Targets Using A Depolymerizing Mandrel

Abstract

A new technique for producing hollow shell laser fusion fuel capsules was developed that starts with a depolymerizable mandrel. In this technique we use poly(alpha-methylstyrene) (PAMS) beads or shells as mandrels which are overcoated with plasma polymer. The PAMS mandrel is thermally depolymerized to gas phase monomer, which diffuses through the permeable and thermally more stable plasma polymer coating, leaving a hollow shell. We have developed methods for controlling the size of the PAMS mandrel by either grinding to make smaller sizes or melt sintering to form larger mandrels. Sphericity and surface finish are improved by heating the PAMS mandrels in hot water using a surfactant to prevent aggregation. Using this technique we have made shells from 200 μm to 4 mm diameter with 15 to 100 μm wall thickness having sphericity better than 2 μm and local surface finish better than 10 nm RMS.