Dynamics of a plasma formed by exploding metal wires and insulator fibres

Abstract

High-current nanosecond discharges through metal wires and insulator fibres were investigated in the NIKE-3 (100 kA, 50 ns) and BIN (250 kA, 100 ns) facilities. Glass fibres were used as an example in a study of the dependence of the discharge conditions on the linear density μ of the load. An increase in μ altered the nature of the discharge through the diode from a mismatched regime accompanied by generation of an electron beam (μ < 4 μg cm-1) to the formation of 'hot spots' (μ = 8–20 μg cm-1) and then to a regime of a luminous skin layer ( μ > 30 μg cm-1). A strong influence of the state of the surface on the nature of an explosion of a metal wire was observed. The experimental results obtained at the beginning of wire explosions were accounted for by a model of the metal—plasma transition. The plasma motion and the development of instabilities of a plasma filament during a discharge were investigated by optical methods. Some of the experiments indicated simultaneous development of helical and 'sausage' instabilities. A two-dimensional ideal magnetohydrodynamic model was employed in calculations dealing with the process of formation of a constriction (pinching) and the results were in good agreement with the observations.