Breakdown of stratified electrical explosion products: Plasma development and its mechanical effect

The physical image of breakdown dynamics inside striations is depicted. High-speed photography along with electrophysical and spectral diagnostics reveals three modes for plasma development in Cu wire explosion: current cutoff, initial breakdown (with quenching), and main breakdown (with re-strike). The growth of spatial heterogeneity by electrothermal instability (ETI) provides a stratified structure before the initial breakdown. The characteristic wavelength of the strata is mu m for thinner wires (d = 90/130 mu m) but in mm level for thicker ones (d = 240/290 mu m). By increasing the stored energy from 200 to 220 J, the 290-mu m-diameter Cu wire experiences a transition from current cutoff to initial breakdown, with a deposited energy of 2.64 and 3.10 eV/atom. Although the energy is not sufficient to vaporize the wire, axial micro-plasma-channels develop among bright layers (higher temperature but lower density), forming a crossed low-conductive plasma-network connecting two electrodes. If the residual energy is enough, the scenario (main breakdown) would be similar to streamer-spark transition and enhance the expansion of discharge channel. Two paralleled wires are exploded simultaneously but only one establishes main breakdown; therein, three stronger shock waves are detected, namely, two for vaporization and one for breakdown.

Automated summary

The study investigates the breakdown dynamics inside striations during Cu wire explosion using high-speed photography and electrophysical diagnostics. Three modes of plasma development are revealed, along with the formation of spatial heterogeneity before initial breakdown. By increasing stored energy, a transition in breakdown modes is observed, with the possibility of enhancing discharge channel expansion if residual energy is sufficient.