X-Ray Radiation from Compact Tungsten Wire Arrays at 1 MA Current

Abstract

We have extensively studied plasma formation, implosion and radiative characteristics of two types of compact load configurations before: compact multi-planar and cylindrical wire arrays <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1, 2</sup> . The experiments with such loads were performed on the 1-1.7 MA Zebra generator at UNR <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1, 2</sup> , and also on the Saturn generator at SNL <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3, 4</sup> . It was demonstrated that such wire arrays of 3-6 mm diameter/width are excellent radiation sources and can be useful for novel ICF applications <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2, 3</sup> , however currently there is very limited research on compact wire arrays. During the last few years, there is also a renewed interest to study hard x-ray non-thermal inner-shell emission from Z-pinch plasmas of high-atomic-number materials on Sandia's Z and NRL Gamble II generators. We present here the analysis of three experiments with W wire arrays performed on the 1 MA Zebra in the same day. Two compact cylindrical wire arrays (CCWA) of 6 mm diameter with a similar array mass <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{m}=91-92\ \mu \mathrm{g}/\text{cm})$</tex> and the same number of wires (one with 24 W wires and another with alternating 12 W and 12 brass wires) and one single planar wire array (SPWA, 10 W wires, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{m}=74\ \mu \mathrm{g}/\text{cm}$</tex> ) are considered. A comprehensive set of diagnostics was implemented. We focus mostly on time-gated hard x-ray spectroscopy of “cold” W L-shell lines (1–1.6 Å) from W and W/brass CCWAs recorded from 10 ns before to 15 ns after stagnation and correlations between their relative intensities and x-ray diode and electron beam measurements. The results are compared with W SPWA, warm dense matter results, and modeling. In addition, Cu and Zn <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{K}\alpha$</tex> lines from W/brass CCWA are investigated in the same spectral range and compared with brass CCWA <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> . Future work on using “cold” W L-shell lines for electron beam studies is discussed.