Optimization of Single and Double Planar Wire Arrays as a Powerful Radiator for Possible ICF Applicatios

Abstract

Summary form only given. An enhancement of energy conversion of the pulsed power source into the radiation from the Z-pinch plasma, and shaping of radiation pulses from a compact (in comparison with a cavity dimension) driver is critical for the Z-pinch driven ICF. A planar wire array placed in the center of the Z-pinch chamber was found to be an interesting for these problems resolution. Recently, experiments with single and double planar arrays (SPA and DPA) from Al, Cu, Mo, and W wires have been performed on the 1 MA Zebra generator at the UNR. The diagnostics include X-ray/EUV diodes, bolometer, time-gated and -integrated X-ray spectrometers and pinhole cameras. In the SPA wires were mounted in a one linear row. The DPA includes two parallel rows with an inter-row gap (2-6 mm) smaller than an array width (5-10 mm). The SPA and DPA can be more compact than cylindrical arrays. The DPA more capable than SPA to shaping an X-ray pulse by changing geometry and material. The DPA imploded even with different material in rows (one row-Al and another-Mo). A scaling of arrays performance with width, material, mass, wire numbers, inter-wire and -row gaps was studied. Hot spots play a significant role not only in a final implosion, but also during an early plasma formation. Non-LTE kinetic modeling of X-ray spectra provided time-and spatially-resolved plasma parameters: Te of 1.3 keV and Ne of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> was observed in hot spots (the Mo SPA.) A comparison with conventional and compact cylindrical arrays is discussed. The total radiation yield (19 kJ and 24 kJ from Mo SPA and DPA, respectively) exceeds the inductive energy change at least by a factor of 4-5. Observed strong small scale plasma inhomogeneity indicates a resistivity of such a plasma as a possible energy coupling mechanism. Wire dynamics model was developed to calculate the implosion dynamics. The 2D (x,y) imploding plasma layer model is used to simulate the radiation yield.