Stability and symmetry in inertial confinement fusion

The asymmetries of spherical implosions driven by direct laser illuminations are of fundamental concern to the inertial confinement fusion community because they provide severe limitations on high gain pellet designs. Theoretical progress on several fronts has recently been made through numerical simulations in providing a more complete understanding of the physical processes involved in these asymmetries and instabilities. The results also suggest methods of controlling these processes and their implications for laser fusion systems design. Stability and symmetry issues have been investigated. Laser matter coupling and scaling laws relating the asymmetry results to spherical pellet designs have been investigated. Principle results include finding (1) the requirements for thermal smoothing of laser nonuniformities, (2) reduced Rayleigh-Taylor growth rates and saturation via the nonlinear Kelvin-Helmholtz roll-up, (3) that perturbation wavelengths greater than the shell thicknesses are most likely to cause an asymmetric implosion, (4) a new theory based on vortex shedding that explains the reduced linear Rayleigh-Taylor growth rates and (5) a possible wavelength-intensity window for direct illumination where the requirements of pellet velocity, symmetry, and efficiency necessary for high gain can be simultaneously met.