Studies of Implosion and Radiative Properties of Tungsten Planar Wire Arrays on Michigan’s Linear Transformer Driver Pulsed-Power Generator

摘要

Wire arrays were widely studied as loads for Z-pinch generators in order to be used for multiple scientific applications. More recently, tungsten double planar wire arrays (DPWAs), which consist of two parallel planes of wires at a distance of a few millimeters, were suggested and tested for indirect drive inertial confinement fusion. Tungsten DPWAs have previously demonstrated the highest (among planar wire arrays) radiation yield (up to 30 kJ), compact size (few millimeters), and strong electron beam production on university-scale highimpedance Marx bank Zebra generator at University of Nevada, Reno. During the last few years, we have reported on the outcome of the experiments with uniform and mixed Al and stainless steel DPWAs on the low-impedance linear transformer driver (LTD) Michigan accelerator for inductive Z-Pinch experiments (MAIZE) generator at University of Michigan. Here, we present the results of the most recent campaigns with tungsten DPWA loads, where the successful implosion of W wire arrays on a university-scale LTD MAIZE generator was demonstrated and analyzed. These implosions were recorded using filtered X-ray diodes, X-ray spectrometers, and pinhole cameras, and a 12-frame optical shadowgraphy system. In particular, tungsten DPWAs with a mass up to 87 μg/cm arranged in various configurations were successfully imploded at a peak current of 0.5 MA during~190-215 ns. The experimentally estimated changes of tungsten DPWA plasma region inductance and total load inductance were correlated qualitatively in time with X-ray bursts. In addition, on shots that demonstrated strong plasma pinching process and Faraday cup signals time were correlated with the appearance of the minimum current-carrying radius of the plasma column. In addition, analysis of soft (4-7 Å) and hard (1-2.4 Å) line radiation indicate keV M-shell tungsten (W) plasma and the presence of electron beams.