Core structure and secondary breakdown of an exploding wire in the current-pause regime

The results of experiments with rapidly exploding thin conductors inthe current-pause regime are presented. Copper wires 25mmin diameter and 12 mm in length serve as loads for a GVP pulsed generator based on a low-inductance capacitor. The generator produces current pulses of up to 10 kA with dI/dt up to 50 A/ns. A 100-800-ns current-pause regime is obtained for charging voltages of 10-15 kV. The discharge channel structure is studied by shadow photography using 0.53-mu m, 10-ns second-harmonic pulses from a Nd3+: YAG laser. In the experiments, three types of secondary breakdown are observed, with different symmetry types, different current-pause durations, and different dependences on the energy deposited into the wire during its resistive heating. All of these breakdown types develop inside a tubular core that is produced in the current-pause stage and that remains almost undamaged by the breakdown. (C) 2019 Author(s).