High-Speed Imaging of Transition from Fluid Breakup to Phase Explosion in Electric Explosion of Tungsten Wires in Air

High-speed visible imaging of sub-microsecond electric explosion of wires at the low specific energy deposition threshold reveals three distinct modes of wire failure as capacitor charge voltage and energy deposition are increased. For 100 micron diameter gold-plated tungsten wires of 2 cm length, deposited energies of 1.9 eV/atom produces a liquid column that undergoes hydrodynamic breakup into droplets with radii of order of wire diameter on timescales of 200 microseconds. Instability growth, column breakup, and droplet coalescence follow classic Rayleigh-Plateau predictions for instability of fluid column. Above 3.2 eV/atom of deposited energy, wires are seen to abruptly transition to an expanding mixture of micron scale liquid-droplets and vapor within one frame (less than 3.33 microseconds), which has been termed phase explosion in literature. Between these two limits, at 2.5 eV/atom of deposited energy, wire radius is unchanged for the first 10 microseconds before the onset of a rapid expansion and disintegration that resembles homogeneous nucleation of mechanically unstable bubbles. Thermodynamic calculations are presented that separate cases by temperature obtained during heating: below boiling point, near boiling point, and exceeding boiling point.