Inertial confinement fusion and fast ignitor studies

Laser imprinting has been studied and, in particular, saturation of areal d ensity perturbations induced by near single mode laser imprinting was obser ved. Several issues important for the foam buffered direct drive scheme hav e been investigated. These studies included measurements of the absolute le vels of stimulated Brillouin and Raman scattering observed from laser irrad iated low density foam targets, either bare or overcoated with a thin layer of gold. A novel scheme is proposed to increase the pressure in indirectly driven targets. By heating a foam supersonically that is attached to a sol id target the pressure generated is not only the ablation pressure but also the combined pressure due to ablation at the foam-foil interface and the h eated foam material. Planar brominated plastic foil targets overcoated with a low density foam were irradiated by a soft ?( ray pulse. The pressure wa s obtained by comparing the rear side trajectory of the driven target obser ved by soft X ray. radiography with one dimensional radiation hydrodynamic simulations. Observations were also carried out of the transition from supe rsonic to subsonic propagation of an ionization front in low density chlori nated foam targets irradiated by an intense soft X ray pulse. The diagnosti c for these measurements was K shell point projection absorption spectrosco py. In the fast ignitor area the channelling and guiding of picosecond lase r pulses through underdense plasmas, preformed density channels and microtu bes were investigated. It was observed that a large fraction of the inciden t laser energy can be propagated. Megagauss magnetic fields were measured, with a polarimetric technique, during and after propagation of intense pico second pulses in preionized plasmas. Two types of toroidal fields, of oppos ite orientation, were detected. In addition, the production and propagation of an electron beam through solid glass targets irradiated at intensities above 10(19) W/cm(2) were observed using optical probing techniques.