Advances in compact wire-array Z-pinch X-ray sources and Z-pinch diagnostics

Abstract

Summary form only given. The Z facility at Sandia National Laboratories is a 100-ns, 20-MA pulsed power driver for plasma radiation sources. Experiments with tungsten wire-array Z pinches on the Z facility can produce >200 TW and 1.8 MJ of soft X rays in the 100-10,000 eV range. The best performance from tungsten wire arrays on the Z facility was originally obtained with 40-mm diameter arrays. As part of a concentrated multi-year campaign studying both single and nested (concentric) wire arrays, we have experimentally demonstrated comparable results using 20-mm diameter arrays, a feat that was not obviously achievable even a few years ago. The use of compact X-ray sources is critical to designs for double-ended, Z-pinch driven hohlraum inertial confinement fusion (ICF) concept. Concurrent with our compact X-ray source research, we have also actively pursued the development of advanced diagnostics for studying Z pinches, such as monochromatic X-ray backlighting/imaging and grazing incidence cameras. Monochromatic X-ray backlighting has played a critical role in confirming models for wire ablation physics and also in verifying the role of rapid current transfer and ablation of the inner wire array in a nested array implosion. These observations helped us develop methods for controlling the radiation pulse shapes attainable from nested wire-array implosions, allowing us to experimentally demonstrate radiation pulse shapes equivalent to those required for fusion capsule implosions. Recent experiments studying single-array implosions have demonstrated high coupling efficiency between the pulsed power and the X-ray pulses from short-implosion-time arrays that appears to be the result of contributions from non-kinetic sources of energy, a result consistent with array-on-rod tests. These diagnostics and experiments have provided us with a wealth of new data on Z-pinch dynamics that is being used to constrain models for wire-array Z pinches