Double Z-Pinch-Driven Hohlraums: Symmetric ICF Capsule Implosions and Wire-Array Z-Pinch Source Physics

Summary form only given. There continues to be dramatic progress in applying pulsed-power driven wire arrays to research in Inertial Confinement Fusion (ICF). The Z facility at Sandia National Laboratories delivers -20 MA to a wire-array z pinch that supersonically implodes the wire-array plasma, and ultimately produces a 100-200 TW X-ray source at stagnation. Wire array X-ray sources appear to be an excellent match to the driver capital cost, hohlraum size, and radiation pulse lengths required to implode the large-diameter (ges 2.65 mm) ICF capsules necessary to achieve high-yield (ges 400 MJ) fusion. Two different z-pinch driven ICF concepts are being studied: the dynamic-hohlraum and the double-ended z-pinch-driven hohlraum (DEH). This talk will focus on progress in achieving radiation symmetry of 2-4% for ICF capsule implosions with the DEH and in our understanding and scaling of the wire-array source. The DEH is the first pulsed power concept to demonstrate ICF-relevant radiation symmetry. In this concept, two wire-array pinches heat two separate primary hohlraums located at either end of a central coaxial secondary hohlraum containing the ICF capsule. X-ray backlighting measurements show control of low-mode radiation symmetry with 2.2-4.7 mm capsule diameters. High radial capsule-convergence ratios of 14-21 have been achieved. Scaling to capsule drive temperatures relevant for fusion will require total X-ray powers of ~2 PW. The DEH approach largely decouples the z-pinch source physics (in the primary hohlraum) from capsule implosion physics (in the secondary hohlraum), allowing independent study of both. This has enabled rapid progress in our understanding of high-current single and nested wire array physics. Experiments have studied the scaling of wire array ablation and implosion dynamics and X-ray power with current, array mass, and current rate of rise. The mass distribution of single and nested arrays has been measured with monochromatic X-ray backlight- ng and laser shadowgraphy. Our improved understanding has led to z-pinch designs with control of radiation pulse shaping appropriate for low-entropy ICF capsule compression.