Expansion of the plasma corona from a wire exploded in vacuum

An experiment was performed with the aim to determine the expansion velocity of the corona that is formed around a wire exploded in vacuum. The corona expansion velocity was found for Al and W wires as the wire current density was increased to 1× 10⁸ -1.4× 10⁸ A/cm². It was estimated by the time at which current started flowing through auxiliary electrodes separated from the wire axis by a certain distance. The measurements were performed with preliminary heated and unheated wires. It has been demonstrated that for unheated wires the expansion velocity of the plasma corona is determined by the expansion velocity of the desorbed gas and approximately equals (7±0.5) × 10⁶, (9±0.5) × 10⁶, and (1.1±0.6) × 10⁷ cm/s at a generator charge voltage of 10, 20, and 30 kV, respectively. For preliminary heated tungsten wires the metal vapor expansion velocity was (4.2±0.5) × 10⁶, (7±0.5) × 10⁶, and (9±0.6) × 10⁶ cm/s at a charge voltage of 10, 20, and 30 kV, respectively.