Laser examination of wire array dynamics on Z

Summary form only given. We present laser shadowgraph "movies" of plasma structures associated with wire array implosion dynamics for several different load geometries and wire materials fielded on the Z accelerator. A sub-nanosecond visible framing camera is used to record 6 sequential frames of laser illumination or plasma self-emission. The strength of these observations is the ability to correlate early ablation features with later stagnation structures on the same shot. Simultaneously, a monochromatic X-ray backlighter was used to probe the wire array plasma at a single moment in time but at a greater density and spatial resolution. This set of complimentary diagnostics provides new possibilities for the direct observation of wire array ablation and stagnation dynamics. We observe a strong disagreement between experimental results and a 0-D compression trajectory. The compression starts later in time and has a steeper trajectory than the 0-D prediction due to prolonged plasma generation. Periodic structures, or flares, form initially at the cathode end of the array with a spatial period of /spl sim/250 /spl mu/m and angle up towards the anode at 9/spl deg/. Correlated with the formation of these flares is the observation, later in time, of lower plasma densities in this region near the cathode. This implosion asymmetry is thought to be responsible for the observed top/bottom asymmentry of the X-ray power. Also occuring during initiation are small explosions which are randomly distributed along the lengths of the wires. These explosions are strongly correlated to regions where mass remains behind which does not participate in the implosion. Even after the main implosion front has passed, this mass remains at the original position of the wires drifting up towards the anode faster than it drifts in towards the axis.