Investigations of the ablation phase of low wire number arrays at 200 kA

Summary form only given. The ablation phase of wire array z-pinch wire experiments driven by fast-rising currents is poorly understood at present. In particular, the of a quasi-periodic modulation in the plasma flow accelerated from the wire cores appears in systems in which both global and local global magnetic are dynamically significant. This structure is observed at all current levels, and is not fully explained. This lack of a complete description of the physical process which drive the ablation structure leads to uncertainties in the scaling of the plasma parameters with drive current. In order to increase confidence in projected performance, data from a range of experiments can be used to benchmark computational codes. Small scale generators have played a vital role in this area during the recent renaissance of wire arrays as a high power x-ray source and possible driver for Inertial Confinement Fusion (ICF) and Inertial Fusion Energy (IFE). We present an investigation of low wire number wire arrays on the 200 kA GenASIS device at UCSD. Laser interferometry is used to examine several materials, and two- dimensional electron density maps of the ablation structure are recovered as a function of both space and time with spatial resolution -50 I????m. Gated emission imaging provides an estimate of the local variation in plasma temperature as a function of radius and axial position, to allow an inference of the ionization state. Experimental data are compared to 3D simulations performed with the GORGON resistive MHD code, which provides a range of simulated diagnostic views to allow a direct comparison to experiments. Results indicate good agreement regarding the mass density variation across the ablation structure as a function of axial position, which is typically a factor of- 1 -2 for wire materials studied to date.