Tungsten Planar Wire Arrays On Michigan’s Ltd Generator

Abstract

Since the first wire-array tungsten (W) experiments on Z at SNL, where the record x-ray power of 200 TW and x-ray yield of nearly 2 MJ were achieved 1, such arrays were actively studied and considered for various applications including inertial confinement fusion (ICF) 2. More recently, W Double Planar Wire Arrays (DPWAs) were suggested and tested for indirect drive ICF 3. DPWA consists of two parallel planes of wires of the same (uniform) or different (mixed) wire materials. W DPWAs have previously demonstrated the highest (among PWAs) radiation yield (up to 30 kJ), compact size (few mm), and strong electron beams at the Universityscale high-impedance generator 3. 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 University of Michigan’s low-impedance Linear Transformer Driver (LTD) MAIZE generator. Here we present the results of the most recent campaign with W and W/Al DPWAs recorded using filtered x-ray diodes, x-ray spectrometers and pinhole cameras, and a twelve frame shadowgraphy system. For the first time, implosion of W wire arrays on LTD generator in USA was demonstrated and analyzed. In particular, uniform W and mixed W/Al DPWAs with a mass up to 87 μg arranged in various configurations were successfully imploded at the current of 0.5 MA during $\sim 210$ns. The most interesting results were obtained with W/Al DPWAs where a long-term standing shock wave was consistently formed at the W side, which was also observed at the high-impedance Zebra generator at UNR. In addition, soft (4-7 Å) and hard (1-2.4 Å) line radiation was substantially suppressed by including the Al plane.