Study on electrical explosion of bare and insulation coated tungsten wires

Summary form only given. Electrical explosion of single wire is the initial stage of wire array z-pinches. In order to study the physical process of single wire explosion, a small-scale pulsed power generator was established, which can provide positive and negative polarity current with the peak value of 3kA and the rise-time from 20ns to hundreds of nanoseconds. The single wire loads are bare and insulation coated tungsten wires with a dozen microns in diameter. The electrical behavior (i.e. the voltage and current waveforms) of the wire explosion was measured by a capacitive divider and a Rogowski coil, respectively. The evolution images of wire explosion were photographed with laser shadowgraph, interferometry and schlieren. A large number of experiments of wire explosion have been carried out on the small pulsed power generator. The results show that for the bare tungsten wire, due to the earlier flashover breakdown along the wire surface, the energy deposited into the wire is less than the energy needed for vaporizing the whole wire, which always results in a heterogeneous structure of exploding wire, i.e. high-density wire core surrounded by low-density coronal plasma. While for the insulation coated tungsten wires, the flashover can be delayed and thus the deposited energy can be close to or greater than the vaporization energy, which leads to a higher wire expansion ratio, and wire core free explosion (i.e. wire material totally vaporized) can be achieved before flashover occurs with suitable current waveforms.