Prospects for 2 mm diameter NIF polymer capsules

The National Ignition Facility (NIF) will require 2 mm diameter shells with a flexible composition profile and variable thickness. These shells must meet out of roundness (OOR) and surface roughness specifications which are at least as good as the best 1/2 mm shells shot on NOVA. These perturbations are generally expected to become worse with increasing diameter, so there is some concern about the prospects of meeting those exacting specifications with shells with four times larger diameters. The PAMS/GDP technique we are currently using for 1 mm diameter OMEGA shells seems capable of producing satisfactory NIF shells. It can produce shells with a wide variety of dopant elements and concentration profiles, and wall thicknesses. Comparing the OOR of NOVA and OMEGA shells made with the PAMS/GDIP process with that of larger shells made of polystyrene by a similar process at the Osaka University Institute of Laser Engineering (ILE) suggests that the perturbations during curing can be less important than previously believed. We see no fundamental barrier to providing shells to NIF specifications. However, process optimization will be required