Color ultrafast photography study of a high-current discharge initiated by exploding a short wire in the atmosphere

In this paper, we describe the ultrafast slit-scanning photography of light phenomena arising at the stage of the electrical breakdown in the atmosphere and in a channel initiated by a wire explosion. The characteristics and features of the photographic registration of the SFR-1 camera using color and spectrozonal negative aerial films sensitive in the visible and near infrared regions of the optical spectrum are presented. Using photograms in color, we were able to visualize small-scale inhomogeneities, a current-carrying channel and its “shell,” emissions of matter, and shock waves in the plasma. This technique made it possible to record a secondary shock wave in the plasma on the discharge axis during the explosion of short (length $\approx$15 mm) copper and nichrome wires with a diameter of 100–150 $\mu$m at a stored energy of $\sim$100 J. At the moment of cumulation in the plasma, a “hot spot” with a minimum size of $\sim$0.5 mm was formed on the discharge axis. It may be the source of narrow-beam coherent radiation with X-ray photon energies of 10–30 keV. The cumulation mechanism is discussed based on the regularities of the $z$-pinch phenomenon in a discharge initiated by a wire explosion.