Different mechanisms of shock wave generation and scenarios of second breakdown development upon electrical explosion of wires

The structure of the discharge channel upon nanosecond wire explosion has been studied using laser Schlieren probing. Wires of 25 μm diameter and 12 mm length were exploded in air and vacuum by 10 kA current pulse having a 50 A/ns rise time. The development of shock waves in the air was observed. The propagation of shock waves was analyzed using a simple model of flat piston. It became possible to draw conclusions the dislocation of the flow of the main part of the current in the volume of the discharge channel. This permitted to distinguish two scenarios of development of secondary breakdown of the interelectrode gap. The scenario (shunting or internal) in accordance with which secondary breakdown develops in each concrete case depends to a large extent on the properties of the material of the exploding conductor.