Different breakdown modes of electrical exploding aluminum wires in air

Summary form only given. Compared to the exploding wires in the vacuum, the air would suppress the expansion of the vaporized metal or impurities and then delay the procedure of voltage collapse. Electrical exploding wires in air are often characterized by a current pause stage before the voltage collapse. In this paper, we will report two different electrical breakdown modes of electrical exploding aluminum wires in air.Based on the 1 kA, 90-170 A/ns negative-polarity pulsed power generator, experiments of electrical explosions of aluminum wires in air are testing and diagnosed by a set of comprehensive diagnostics, including fast photography, optical streak photography, optical emission spectroscopy (OES), focused shadowgraphy, schlieren, and Mach-Zehnder interferometry. At a low charging voltage, current pause is observed with a fast moving shock wave front and a much slower expanding plasma column. But with a higher voltage, current pause disappears and the plasma edge just beside the shock wave front is observed. We think the phenomena may come from different voltage breakdown modes with breakdown channels located in the air and the exploding wire respectively. The differences of the ohmic energy deposition, expansion rate of the shock wave front and exploding wire, and plasma emission spectroscopy from the two electrical breakdown modes are also compared.