Resolving Conductor-to-Plasma Transition Through Low-Energy Electrical Explosion of metallic foils

Abstract

Electrical explosion of metallic foils involves a rapid transition from solid-state conduction through melting and vaporization to formation of an ionized plasma. Resolving intermediate processes is challenging because these transformations occur over strongly overlapping timescales. In this work, to examine temporal evolution of conductor-to-plasma transition, electrical explosion of Al foil is investigated under two controlled energy-deposition regimes. At higher energy deposition, synchronized current, voltage, and fast-framing optical measurements capture explosive destruction of foil and subsequent plasma formation. However, underlying intermediate processes remain temporally compressed. To resolve these processes, experiments are performed at a lower energy-deposition rate while maintaining comparable circuit timescales. Under these conditions, characteristic features in the electrical waveforms allow successive stages of heating, melting, liquid-phase evolution, vaporization, and vapor discharge to be delineated. Experimentally determined action integrals associated with observed transitions are compared with predictions based on the Tucker Toth specific-action model and available literature. A particularly notable observation is a sharp voltage turnaround immediately preceding current re-strike, occurring simultaneously with increasing current and reproducibly associated with plasma formation. Although its physical origin remains unresolved, the feature suggests a rapid nonlinear reorganization during final transition from exploding conductor and metal vapor to plasma conduction. Results demonstrate that controlled energy-deposition rate provides an effective means of temporally resolving processes otherwise compressed and offers a useful approach for investigating the dynamics preceding plasma formation in electrically exploded foils.