Direct drive double shell target implosion hydrodynamics on OMEGA

Imploding indirect-drive double shell targets may provide an alternative, non-cryogenic path to ignition on the National Ignition Facility (NIF). Experiments are being pursued at OMEGA to understand the hydrodynamics of these implosions and the possibility of scaling to NIF designs. We have used 40 beams from the OMEGA laser to directly drive the capsules, and we have used the remaining 20 beams to backlight the imploding shells from two different directions at multiple times. We will review the recent experiments to measure the hydrodynamics of the targets using two-view x-ray radiography of the capsules. We will present data on measured yields from the targets. We will present a measured time history of the hydrodynamics of the implosion. Experiments were pursued using direct drive in which the M-band effect, experienced in the indirect drive experiments, could be eliminated or controlled. It was learned in the direct drive experiments that the best performing capsules were those that had a thin outer layer of gold. This effectively causes M-band pre-heat effects giving implosion hydrodynamics and performance closer to the indirect drive case. We will review the method used to radiograph the targets and the techniques used to extract useful information to compare withmore » calculations. The effect of imperfections in the target construction will be shown to be minimal during the initial stage of the implosion. The yields from the targets were observed to be uniformly low compared to indirect-drive.« less