Review of indirect-drive ignition design options for the National Ignition Facility

Several inertial confinement fusion (ICF) capsule designs have been proposed as possible candidates for achieving ignition by indirect drive on the National Ignition Facility (NIF) laser [Paisner et al., Laser Focus World 30, 75 (1994)]. This article reviews these designs, their predicted performance using one-, two-, and three-dimensional numerical simulations, and their fabricability. Recent design work at a peak x-ray drive temperature of 250 eV with either 900 or 1300 kJ total laser energy confirms earlier capsule performance estimates [Lindl, Phys. Plasmas 2, 3933 (1995)] that were based on hydrodynamic stability arguments. These simulations at 250 eV and others at the nominal 300 eV drive show that capsules having either copper doped beryllium $(\mathrm{Be+Cu})$ or polyimide $({\mathrm{C}}_{\mathrm{22}}{\mathrm{H}}_{\mathrm{10}}{\mathrm{N}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{4}})$ ablators have favorable implosion stability and material fabrication properties. Prototypes of capsules using these ablator materials are being constructed using several techniques: brazing together machined hemishells (Be+Cu), sputter deposition (Be+Cu), and monomer deposition followed by thermal processing (polyimide).