Investigation of two-step precursor formation in multi-planar wire arrays on the 1MA Zebra generator

Abstract

Summary form only given. The double-planar wire array (DPWA) is the most promising Z-pinch load studied on the Zebra generator for application to radiation physics and inertial confinement fusion studies. These loads radiate powers and energies up to ~1 TW and ~25 kJ, respectively, in a versatile pulse shape on the 1 MA Zebra generator. Recent studies show that radiation yields of this load scale near-quadratically with currents ranging 0.8-1.4 MA, and that maximum powers were obtained with the Mo DPWA at the minimum inter-planar gap studied: 1.5 mm (6 mm width). This scalability with current and dimension, along with superior yields, make the DPWA attractive for future studies on larger, pulsed-power generators. Initial investigation of this load revealed unique implosion dynamics: each plane implodes independently into two off-axis columns before coalescing into the final pinch. New results are presented exploring the formation of these off-axis plasma columns with laser shadowgraphy and time-gated X-ray imaging, each fielded along the radial line of symmetry. The wire ablation dynamics model (WADM) is used to show new details about the precursor formation and implosion of DPWA loads composed of Al, SS, and W. The WADM was used with combined-material nested cylindrical wire arrays to show an ablation dominated implosion regime. This technique is applied to combined Al/SS and Al/W DPWA to study ablation effects on the formation of the precursor and implosion. This analysis is then applied to the triple-planar wire array and the new, skewed-wire, DPWA with axial magnetic field. Finally, results from the analysis of Al/SS DPWA time-gated spectra are presented.